Ok guys I know you have all heard this before but I am pissed now. Took a trip to Pismp this weekend going up the grades pulling 2 quads and a golf kart and a quad in the back of my truck my transmission and engine both dored up to the red zone. I only have 4,000 miles on my truck its an 04.5. Now I was think about buying a toy hauler but those dreams were crushed on this trip. I would like to know what you guys are doing about your problems and see if you can give me any advice on what to do. Thank You

go to this forum,


http://www.gm-diesel.com/


look down through the topic Duramax Diesels


look for the thread Update to my hot running LLY


read about that gentleman's experience


GM is starting buybacks when you have all you ducks in a row and can prove the issue. be nice and polite. get all your evidence together. make sure there are no modifications that can be blamed for the problem and go from there


dave

Wait a second, you must have a problem with your truck. I pull a toy hauler in AZ where it is hot as hell and it does get hot,but nothing close to the red zone. Pulling an open trailer with that kind of load and over heating, there is something not working as it should be. Take it to the shop and let them correct whet ever is currently missed up. REMOVE the Edge before it goes in any shop!!!!!


DAN

Just curious, was that with or without the Edge? Edited by: Bill Gisse

Yeah, what dwrat said! http://www.dieselplace.com/forum/smileys/Approve.gif I'm towing a 40' triple axle toy hauler with GCW of 24,500lbs with no overheating issues. Yanks it up and pulls it down the highway very easily. The truck will run up to 230* engine temp, 200 tranny temp, when pulling long grades or mountains in hot weather but goes right back to normal operating temp afterwards. Never anywhere near the red zone! http://www.dieselplace.com/forum/smileys/Thumbs Up.gif So far, so good!


Ditto what Gisse asked. Is the edge/juice the only upgrade you have done to your truck? Bigger tires? Brush guard? Aftermarket grille?


It's a new truck, if you have any concerns or issues they are on GM's dime. The only down side is you will likely be without your truck while they putz around with it. My experience with dealer techs in my area is few are very well versed with the DMAX or Allison. If you find a tech that is stick with him, or her? http://www.dieselplace.com/forum/smileys/HiHi.gif Politically correct! You will also be establishing a record in GM's database for any future issues. Good luck! JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

This past weekend I pulled a 40' triple axle that Grossed about 11,000lbs, it was 86-88 degrees according to the temp in the rearview mirror, the terrain was mainly flat except two moderate grade hills (5-6%) and about 3/4 to a mile long I watched the gauges very closely because of others complaining about overheating the truck never went nor never touched the 210 degree mark and the tranny never hit 200 degrees. The trip was about 100 miles one way...

Read some of the posts in the engine temp section and you will see you are not alone.

JJ i'm running about the same temp's as you only i'm on the west coast. I did the same trip to Pismo Beach 2 weeks ago pulling my 28'TB with a 8500lb gross at 70 mph. It was 90*.

Same here came back from Pismo LAbor day wkend 26' Wanderer w/ 3 quads, probably around 8500-9000 lbs Ran the same temps as JJ and, my truck is boner stock! I pulled the hill at 40-45mph thought, I didn't want to push it to hard!





JLewhttp://www.dieselplace.com/forum/smileys/HiHi.gifEdited by: screaminjlew

huntsalot, JJ's in his anal mode! http://www.dieselplace.com/forum/smileys/HiHi.gif Do you recall exactly what the engine temp, tranny temp, rpm's and speed were when it entered "the red zone"? Also any add-on's to the front grille area?


As you can see from the other posts several guys are pulling heavy with these LLY's and not overheating, yet some are and we're trying to figure this out on another post (engine temps). JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

No overheating problems at all here. Pulling 6.5% grade, 5 mile long hill.


10,500lb 5th wheel. Engine temp will stay at 200 Deg. Trans will go up to 200 Deg. and Never Move from there. The engine fan comes on and keeps things nice and cool.


Now if I can just keep everyone else out of the passing lane!!!http://www.dieselplace.com/forum/smileys/Evil Smile.gif

http://www.dieselplace.com/forum/smileys/Confused.gifI think that all LLy owners owe it to themselves to hook up a trailer and see how their trucks do. There are tons of complaints in on this forum as well as others. Some experience a problem and some don't. We need to figure this out for GM, as it will have adverse affects on resale value for ALL 2004 LLY trucks. I have been reading the posts on this subject every night. I know that myself and a good friend ordered our trucks within a week of each other. We took delivery of them at about the same time, late July. First thing we noticed was that both trucks had the fans running about 80% of the time. I bought a toy hauler that weighs 10900lbs loaded and he has a 5th wheel that weighs 7000lbs. Both trucks pulling hills heat up to nearly the 260 mark. Even with the weight difference they act nearly identicle. It also seems that for our 2 trucks that the outside air temp has made fairly little diff in engine temp while pulling. I have had my truck in the shop several times for various problems and this last time I told them of the heating issue. I also called GM cust service with the heat complaint and they have been very interested in what the dealer finds on this(many, many phone calls to the dealer). GM wants me to saddle up my trailer and take them for a ride to show them what's happening. I am going to and so is my friend. See I really like my truck, and it makes me real upset to like so many things about the truck only to have a few extremley critical things ruin it. With as many people as have posted about the fan always running, I woulld guess the majority of those people would experience the same temp problems as us if they tried putting their truck through it's paces. It's the old squeaky wheel gets the grease thing. They put thier efforts were they are needed most, lets help focus them on our problems. I bought a truck that was advertised to pull upto 15000lb but I must have missed the fine print that said - only on level groung, under 30mph, air off and never when the sun is out. I just want our trucks fixed.

Driveing today flat ground 89 outside and trans goes over 200 and temp goes over 210. and I took out my hole edge system this is making me sick to my stomach and very upset. I had 2 foeds that went back as lemons so I go and buy a dmax and this is what I get I wish I just would of got a 6.0 now.

Huntsablot, No, no, no! The D/A combination in these trucks is awesome. Check the forums for a good mechanic in your area. There is also an "Ask the Tech" forum. These trucks have 2 thermostats, one might be sticking or just bad.


As for the 6.0, several weeks after I got my truck I had to leave my truck with the accessories guys to install some stuff. The owner loaned me his 2004 Silverado with the 6.0 to drive. Acceleration was awful compared to the D/A, actually almost got nailed pulling into traffic due to the lack of getting the power to the wheels like the D/A. Gas mileage was horrific! My truck gets 15-16 around town and 18-19 on the road. Try 10-12 around town and a whopping 14-15 on the road. Ouch!http://www.dieselplace.com/forum/smileys/Pinch.gif


Have your issues addressed at the dealer. If they can't fix it then GM may owe you another one. The overwhelming majority of D/A owners aren't having this problem. Good luck! JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

I was also told that this was the truck of choice for pulling a load of 15000lbs. But what they didn't say, if you have to climb a hill, all of your over heat gauges will climb with you and all of your warning lights will come on to warn you that you are preparing to "walk". I live in the San Joaquin Valley and the only way to get out of here is over a hill. The truck has been to the dealers service 3 times and 1 test drive up the ridge route. I didn't buy it to take it to the shop. And yes, he did see the temp gauge and the light on. He said they are designed to run hot.. I don't think so!! This is my 3rd diesel truck. Two Fords before and no problems..I told the service manager that if I wasn't pulling anything or didn't have any hills to climb, I would have never known that this truck had a problem. On the flat and down hill this truck is a dream to drive.. With this over heat problem, what about the log term affect on all the engine and transmission "seals"????? A couple of years and we will have many oil leaks.

I would agree to the statement that the majority of people are not having an overheating problem. I would also say that the majority are not pulling large loads up hills. Maybe this problem is not on every truck, but it is on a lot of them. Some are worse than others. This could be driving style. The only not statistical facts that we have here are that there is a problem with some LLY trucks overheating and that all LLY trucks are designed to run hotter than the LB7. They changed the pitch of the fan (see noise) to try to account for it. If you have this problem, keep beating up your dealer. If you don't have this problem, and don'thave a solution to the problem....


GM will not figure out the problem if there is no noise from the users. If you are towing heavy up big hills without heat problems, I would be curious to know things like build dates. Maybe there is a bad batch or something. Someone once sugested casting issues.


Basically, this horse is beat. Fingers has done a whole lot of testing trying to figure it out. Dealers are shrugging their shoulders. Some guys are getting buy backs with the aid of lawyers. I say advertise for GM! They will eventually fix it. I am not going to ruin my truck in any way until they do. That is my only choice.

I may not be “towing” a big load up hill, but I have a camper that sits in my bed that weighs a lot more than the sticker in the glove box says I should haul, and I drive 70mph up LONG grades and mountain roads with very little climb in temps.

2004.5 lly GMC 3500 CC

I have 2 2004.5's and both over heat when pulling. Really bad on 1,(pull over and wait to add water BAD), minor so far on 2nd. New 4" exhaust, (no cat), on 1 seems to have helped milage, power, and dropped temp a little. Too early to verify. Great system installed by Warp Speed Performance in Rogers, Arkansas. EGR plate hurt mileage, but also helped temp problem. Edge box helped temp when loaded heavy. Have not tried Edge or EGR plate since exhaust was put on. I wanted to get accurate info on what helped and how much. Edited by: RickDLance

Ditto what Exford said! http://www.dieselplace.com/forum/smileys/Clap.gif There are LLY owners out there towing well above GCWR, then there are LLY owners that can't tow 10k lbs without running high temps. GM needs to nail this down, and we're the best testing ground they have. Need to find a "win-win" solution for both.


gtay1234, I like your dealers approach, sounds like they are willing to listen and seek a resolution. If your LLY's fan is engaged 80% of the time there is a problem with too much heat building up in the engine compartment. I rarely ever hear the fan engage unless I am towing my 5ver (24,500GCW). I'm not exactly certain what the build dates will tell us, but tell me where to find it and I'll post it. Are all these trucks built at the same assembly plant (Mexico?)? Is your truck still stock, if not what changes have you made?


I do feel for the guys experiencing the overheating problems. http://www.dieselplace.com/forum/smileys/Hug.gif I would be sick if my truck was doing this to me after spending that kind of money. I'll check some other diesel sites to see if they have any insight.


JJ's out! http://www.dieselplace.com/forum/smileys/Big Smile.gif

The door sticker will get you your build date. It would be nice if we could tabulate the people who are doing fine and the ones that are over heating (or just getting to hot) and see if we can find some similarities.

The only date I saw was 05/04? Not sure if that means May the 4th, or just May of 2004. JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

Both my truck and friends trucks were built 06/04. The only mod I have done is 285's. Same with friends. Fan ran all the time with the 245's befor I changed. Today is the first day that I have been able to really drive the truck in about a week and a half. It's been in and out of the shop for some front end problems. I will give GM some credit, they seem to have tried hard to help - I appreciate that.

My build date is 04/04.

3/04 and so far no REAL problems...4500 miles.

exford, so far ktduramax's LLY was built in March, yours in April, mine in May. March and May report no problems, does your April Duramax have problems? If this is the case what could have happened in April on that production line? http://www.dieselplace.com/forum/smileys/Ermm.gif


I did a totally unscientific experiment yesterday.http://www.dieselplace.com/forum/smileys/Geek.gif My LLY was good and warm from my wife running errands. I found a 3 mile section of 2 lane highway, set the cruise at 60mph, OD engaged, outside temperature range 90-92*. Engine temps stayed right at 200-205*, tranny at 180*. RPM's around 1800. I turned around and drove the same route back with OD disengaged and cruise set at 60mph. Engine/tranny temps were the same on the way back, even with higher RPM's(2500).http://www.dieselplace.com/forum/smileys/Ermm.gif


I expected the temps to be a bit lower given the faster circulation of fluids into/out of the engine and tranny and higher fan speed. Maybe I need a longer run to see any noticeable results. Then again the engine was producing significantly higher HP at 2500rpms versus 1800 which likely meant more heat.


One thing appears consistent though, the thermostats are keeping temps consistent in my LLY at both operating ranges. I'm suspicious of the thermostat's on the LLY overheats! If I recall correctly there are 2 thermostats on the LLY's with different operating ranges. If 2 of the higher temp thermostats were put into an LLY, what impact would this have?


Is it possible that the wrong box of thermostats was layed out in the production line in April? If 2 of the higher temp thermostats were installed this would not allow the water to exit the engine to the radiator soon enough to be cooled sufficiently before it is reintroduced back into the engine. End result, OVERHEAT! http://www.dieselplace.com/forum/smileys/Ermm.gif


Before you techies have me for lunch, my original disclaimer still applies: JJ IS "MECHA-NICKEL-ALLY" challenged so it is totally within reason that my analysis is full of holes, BUT I'M TRYING!


Quick way to find out, plus they are real easy to change out! Other thoughts? JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

JJ do u have J/A in your truck?


I see a hair under 210* pulling loads on truck gauge and 180s at the attitude.


So something w/ the temp gauge isn't right.

I have had my thermostats changed and still overheats.

DMax 10, no juice/attitude, I see the same temps as well.


RickDLance, CRAP! http://www.dieselplace.com/forum/smileys/Cry.gif Are you fairly certain the proper thermostats were put in? I don't have a lot of confidence in the dealer mech's with the duramax's. If yes, then back to the ole drawing board. JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

Quick update! I posted on the "Ask the Tech's" forum and one suggested this may be caused by too much fuel being combusted by the LLY's. One commented that if you are getting lousy MPG's and your LLY doesn't smoke a lot, the LLY is combusting all the diesel fuel which will result in higher engine temps. http://www.dieselplace.com/forum/smileys/Geek.gif Kinda makes sense.


SSSSSSSSOOOOOOOO, those guys experiencing high engine temps or overheating are you getting lousy mpg's or excessive smoking from your LLY's? I also wonder if engaging the tow/haul mode in anyway affects the fuel ratio? BTW, GM has a reflash out that is supposed to improve either fuel delivery or efficiency, something like that. JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

My milage has been loaded with 10000lb trailer 7.5 consistantly. Empty the best I have ever averaged is 14.7. I only see smoke when I first romp on it and not a lot like other trucks. I, when pulling can make it heat way up at will. When climbing just keep my foot in it and it's to the red. Every person that I've talked to here in my area that has a LLY has a similar story to mine if they pull anything. Also friend told my he talked to his dealer about this problem because he is sick of this crap and they told him to sit tight because a solution is in the works. I sure hope so.

I never see any smoke. Unloaded, with mostly freeway driving (70 – 75 mph), I am getting 15 mpg. Towing with a 10k 5er, I get about 10 mpg. This is after I adjust for tire size, I use the following site for calculations; http://www.4lo.com/4LoCalc.htm

I too can heat it up at will while towing. After calling the GM customer assistance number last week they did not admit to any previous complaints and made a 3 way call with the SM at my dealer and I have an appointment to take a ride with the SM this Friday.

I don’t want my money back or another truck, I want my truck fixed! My truck was produced in March of 2004.

http://www.dieselplace.com/forum/uploads/Z_Web_Wildcat_004.jpg

Nice rig cadent45. Both yours and gtay1234's LLY's fall in line with what DH in AZ suspects. I'll go back to the "Ask The Tech" forum to see if anyone knows what the reflash does. Will advise. JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

My status. Pulling trailer 9.5 mpg. Empty? somewhere around 14, not good statistics cause I am not usually empty. No smoke unless idleing for a long period of time. It will get hot on hills if I push it.

I have been following the overheat issues here since they started and I am a little worried, BUT, my truck was built 02/04 it is an LLY, I pull a 30' 7000LB trailer. Everytime I go anywhere I pull decent sized hills. I pull Trappers loop in Utah which is 7% one direction and 8% the other and it is pretty long and I do not over heat, I watched my temps last time to be sure and the highest I get is just barely past the 210 mark. I also pull Daniels summit which is 6% but pretty long and my temps are the same.


I just got a rack for the bed of the truck that hold 2 ATVs and will be pulling the whole load in two weeks so I will see what my temps do.


My truck is stock except for 285s. Hopefully I don't have or get the problem.

Falkirk, the law of averages is on your side. The majority of LLY owners do not appear to be experiencing the overheating issue. Enjoy your family, your truck, have a great trip and drive safely! Just watch your GVWR, GAWR, GCWR and those gauges! http://www.dieselplace.com/forum/smileys/Approve.gif


Back to business! Maynard PM'd me with the following message. While he is not having the overheating issue with his LLY, he did have the reflash done. He states: The reflash that's being done to LLY's is to recalibrate the injectors. I had been working with a Bill Carnaballi(sp), who is the GM/Duramax Quality Manager, to solve a rough idle situation when the engine temps were between 160-180 degrees. GM is aware of the problem and up until a few weeks ago the solution was to replace the injectors. I had all eight replaced and so far so good. My MPG has also increased by about 2mpg. At the time(June/July) they were working on a software fix to calibrate these injectors in the vehicle to avoid costly replacement of injectors that were for all intents and purposes fine. Im not sure if this would affect engine temps as was suggested but Im no authority either. I can say that I was towing 8500# or so for three months with a "bad" (#2 was over-fueling due to calibration problem) injector and not once did I experience any engine temp problems. This includes some pretty hilly conditions as well. Not sure if any of this helps but good luck. THANK YOU MAYNARD! http://dieselplace.com/forum/smileys/Hug.gif


He is going to PM me the phone number for Mr. Carnabelli. Now we need someone from the forum that knows diesel engines, coolant design, etc., inside and out to talk with him. Any volunteers before JJ starts PM'ng you guys in the know?http://www.dieselplace.com/forum/smileys/HiHi.gif You know you don't want me talking to him, ddddddduuuuuuuuuhhhhhhhhhhh! http://www.dieselplace.com/forum/smileys/Wacko.gif JJ

Most I ever pull is about 5k. Never any probs here in mi (no hills), but when on vac last month in PA, boy did I pull some hills. No overheating probs, but man were the EGT's insane--edge/*** set at level 1 or 0 and the thing was hitting backdown all the time (max EGT set at 1300) Course these were steep hills and I was maintaining 65mph. Gotta try an exhuast next. Are you guys calling 210 engine temp overheating? Cause that ain't overheating--it ain't overheating till vapor is pissing out the rad!

I'm going to call mine the 4th stage of overheating. The first stage is a warning on the odometer readout panel. The second stage is an audible alarm with a differant warning on the odometer readout. The 3rd stage is a noticible loss in power (controled by the ECM). The fourth and final stage which I have hit 6 times now is sitting along side the road waiting for it to cool and adding water!!!

redneck45, no we're not calling 210 overheating! What do we sound like, rednecks?http://www.dieselplace.com/forum/smileys/HiHi.gif Overheating is either when your radiator burpshttp://www.dieselplace.com/forum/smileys/Throw Up.gif or your overheat light comes on. This normally happens around 260*.


At 65mph the EGT's you were seeing sound too high given that you weren't pulling anything and the EA was backed down. Most of those with overheating LLY's appear to do so while towing fairly heavy, like over 10k lbs.


Thanks for your input. JJ http://www.dieselplace.com/forum/smileys/Big Smile.gifEdited by: JJs DuMax

Yea, I would say 260 is a bit high. Not sure whats up with my EGT's--these were big hills though.http://www.dieselplace.com/forum/smileys/Confused.gif

I have flat DOGGED the CRAP out of my truck both empty and towing. Empty I have raced against a gasser truck with mods, this went on for a good 10 miles, most of it foot to the floor on a 96* day many times foot was on the floor for 30 second intervals cause I didn't want him catching me (he didn't!). I have also ran it really hard towing my boat for a good 130 miles. I have never pulled the weights that you guys are talking about, but my temps are never much out of normal. The fan does come on sometimes but never for more than a few secs and it always shuts off as soon as the speed rises (fans don't do much over 30 or maybe 35 mph anyway, hell my old firebird was ok when the electric fan died as long as you didn't sit still long and was able to get over 20mph when moving. Ran it that way for months when I was way younger and couldn't afford a new fan!)

The temps did climb a bit to maybe 215 engine and just over 200 tranny during the extended racing game, but letting up a bit while he caught back up was enough for them to fall right back where they sit on a normal day when its all warmed up. I have a hard time believing that my truck would overheat based on its performance so far.

I get the good mileage so maybe there is a correlation to the warmer temps and the trucks that get crappy mileage. I am gonna talk to some friends and see if I can borrow a heavy load to go run up and down the Fred Hartman bridge over and over to see if my truck will get hot as it is plenty steep and long. There aren't any real hills around here other than that for me to make a useful comparison otherwise.

If it overheats I will be VERY suprised.

Redneck, what is the attitude reading for engine temps compared to factory gauge?

TxChristopher, must be the bug deflector!http://www.dieselplace.com/forum/smileys/HiHi.gif Many of us LLY owners can put our foot to the pedal and never see temps above 205*, that is until we slap some serious weight behind it. In my case a 16-17k lb 5ver. To date I haven't experienced the overheating problem, OR maybe I should say I haven't ran into the wrong set of circumstances for it to overheat.http://www.dieselplace.com/forum/smileys/Geek.gif We're trying to figure out why some LLY's are overheating through our dialogue. Welcome! http://www.dieselplace.com/forum/smileys/Big Smile.gif


Your boat is too aerodynamic to create any serious drag like a trailer will. With my dually I forget the dang thing is back there most of the time. I'm thinking I'll have my father-in-law sit in the boat and jump up and down so I'll know its back therehttp://www.dieselplace.com/forum/smileys/HiHi.gif. He's a sport!


I doubt pulling your buddy's trailer is going to bring anything new to this issue that we're not already aware of. But if you just want to satisfy your own curiosity???? http://www.dieselplace.com/forum/smileys/Ermm.gif If your not used to towing heavy please be careful.


On your Quad 110, do you know if it changed your fuel pressure settings at all? Does it monitor engine temps?


JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

You may be right about the boat being aerodynamic, especially with the cover on it, but I have also been on it pretty dang hard pulling horses and that horse trailer is more like raising a sail to pull against. Still the weight of either haven't been in the ranges you guys are discussing nor do I have big hills to climb.

The quad changes the fuel mapping (pulse width, pulse timing, and pulse duration) and seems to have command of the turbo. I doubt it does anything with the fuel pressure, at least as far as I know. It doesn't monitor anything, its a tuner and after it flashes the PCM there is nothing left behind to display.

I don't think that testing it with a buds heavy trailer will bring anything out either, but you never know. I have had cars with cooling syatems that were barely adequate in the past, most notably my 1989 IROC-Z 350. Driving it hard like I did against that chevy gasser the other day would have heated it up VERY quickly and I am sure it would have puked, that's why I feel my truck has had some pressure put on it enough to get a whiff.

I had already read all 11 pages of the other thread concerning hot running LLY trucks before this one. I am of the same opinion as fingers, I expect my 40k+ truck to do what GM claims. That's why I plan to latch onto a 10k to 15k load and do laps over the Fred Hartman bridge. I pulled the boat over that bridge one time with the boat full of water (another story) and at full throttle I was losing speed. Dunno what it weighed that day but it was MOST noticeable and if it had 1000 gallons of water in it I wouldn't be suprised as the entire hull was FULL. The fan came on that day and it was hot outside, but the temps didn't seem to move much. At least I didn't notice them, and I know I would I monitor all gauges when I drive.

Dunno what the grade is of that bridge but I assure you it is plenty long and plenty steep, it is the largest cable stay bridge in the U.S.

I will be careful and hit it on a weekend so it will be clear and during a hot day to see if my truck crys or just does its job. I would think 3 or 4 or 5 consecutive passes over it flat out would simulate some of these grades others have discussed.

Oh yeah, I also built a 1980 Triumph TR7 with a Chevy 350, turbo 350, and chrysler 8 3/4 rear. That car was a real bit*h to cool, having that closed nose didn't help. Even after I went through many diff rated electric fans (pushers and pullers and even both at the same time), high flow thermostats, high flow water pumps, and even had a custom 6 row radiator made for it the system was marginal at best. If I ran it ANYWHERE near hard as I have my DMAX the windshield would be covered in coolant. It ended up being reliable (the cooling system) but not for real hard running, that's a one off type vehicle so issues are to be expected. There should be NONE on our high $$$ new trucks.

Just my .02

;)

Mine got the warning light only once. Combined weight just over 17,000, ~5000ft altitude, 6%+ grade, 111 deg air temp, running 75mph in 4th. As soon as I shifted into 5th, no more problems.

I have done the reflash on my computer with good results. I also have pulled the EGR valve which I feel has made a difference. I know this because I raced a truck like mine, other than I had the codes and 285's. I took off and pulled out to a cab length lead and from there slowly pulled away from him. So the codes do not detune your truck. My truck idles and run alot smoother. So do It!

Gomax, did your LLY ever run high temps, like over 230*, and if so is there any notable difference in engine temps after the reflash? JJ http://www.dieselplace.com/forum/smileys/Geek.gif


TxChristopher, I just have to know how your boat got filled up with water, and why you didn't drain it before putting it on the road? http://www.dieselplace.com/forum/smileys/Ermm.gif

LOL inquiring minds wanna know.....

Ok :)

It had been a couple weeks since we had last taken the boat out. So we figured lets go grab it and run up to Lake Houston and cruise around for a bit, see what we can find. So we run over to storage and hook up the boat and head out. Stopped and filled the truck and the boat up with fuel, and when pulling out of the station had to stomp on it to quick cross three lanes of traffic to get to our three lanes cause a particular car was coming faster than the rest. The truck broke the tires loose trying to get going quick then bit hard and seemed to bog somewhat against the weight but still pulled hard and accelerated decently. I was like "hmmmm that was different" but shrugged it off.

Fast forward about 30 minutes later and we are coming up to the Fred Hartman bridge. I had the truck set on cruise at 70mph as we hit the beginning of the bridge. Now this bridge begins to rise, gets a little steeper, then really gets steep as you head up to the cable stay sections. On the initial grade the I could feel the truck beginning to work against the weight. "No big deal, cruise will handle this" I thought. Started into the second part of the rise, which is a little steeper, and the cruise was losing ground. "Oh well she will downshift in a few secs and she'll recover" I told myself. When the big climb hit we were down 5mph and sinkin fast, the truck downshifted instantly and it was obvious the cruise wasn't gonna keep up so I took over with the foot.

Well, I started to get into it slow at first but the speed was still dropping at a good clip so I mashed it to the floor. "We'll gain speed now. Hah!" I thought.

By now I was midway through the steepest part and under full throttle I lost 3 more mph before it fought to a draw and the rise started to subside so the battle was over.

"Damn that bridge is meaner than I thought and my truck is sure weaker than I thought".

:)

Got to lake and started prepping boat. First thing turned on main power and engine compartment vent fan and automatic bilge pump. Water starts coming out of the side from the pump right away. "Hmmm, must be a little water at the bottom of the bilge" and went on getting stuff ready to deploy, like fenders etc etc. Wifey is in the boat putting the detachable face stereo on and asks me "where does all the water comes from that is being pumped out", and I explain that when we got the boat they didn't have any covers for it and that our cover is on backorder, so when it rains water gets in it. She looks around and says "but I don't see any water in here" so I say "well it rains in here but the water goes below deck thru all these different doors in the floor, like this big one up front that holds the skis and wakeboards"

I open up the ski hold in the floor to show her and it is FULL of freakin water!

I literally said "oh sh*t" and turned and looked and there was a small lake being formed by the STILL running bilge pump. Quick opened the next one down where the fuel tank is.....FULL OF WATER......oh damn......opened up the engine compartment........TOTALLY FULL.

Jumped off the back of the boat and WTF the drain plug is already in???????

Pulled the plug, of course water is gushing out of it. It took the pump and the plug right at 25 minutes more from that point to get all that water out of the boat.

I can't say enough that I have a routine, we prep the boat and put the plug in and then launch. When we are done the first thing I do is pull the plug. I explained everything to my friend who had borrowed the boat the weekend before, but he forgot to take the plug out and I wasn't used to checking for it being in because I always know its not in from the time before.

So all week it had rained its azz off and basically it filled the boat like a big azz washtub.

:)

Dunno how much water was in there, but it was a bun

JJ, yes my truck does run over 230* and NO there is no noteable difference in temps. Currently in the process of having my truck bought back. I wanted them to give me a time frame of when the overheating will be fixed, and they could not do it. Would rather keep this truck, but not the overheating.

My truck never gets over 195 on the Attitude. Factory gauge looks to be around 200. Don't think I ever saw the tranny get to 200.

Yea, I would say 260 is a bit high. Not sure whats up with my EGT's--these were big hills though.http://www.dieselplace.com/forum/smileys/Confused.gif


I can reach 1425* with stock motor.......pulling 8,000lbs up 6% grades...

Anyone know how accurate the factory temp guages and temp senders are. My LLY runs at about 205 up hill and down or stuck in traffic when it's 116 degrees or near freezing. This is with a moderate load in the bed but free of a tow. Reading of all the variances in temps I really wonder how good these guages are. Low bidder out-sourced stuff for sure. Edited by: aka108

I have flat DOGGED the CRAP out of my truck both empty and towing. Empty I have raced against a gasser truck with mods, this went on for a good 10 miles, most of it foot to the floor on a 96* day many times foot was on the floor for 30 second intervals cause I didn't want him catching me (he didn't!). I have also ran it really hard towing my boat for a good 130 miles. I have never pulled the weights that you guys are talking about, but my temps are never much out of normal. The fan does come on sometimes but never for more than a few secs and it always shuts off as soon as the speed rises (fans don't do much over 30 or maybe 35 mph anyway, hell my old firebird was ok when the electric fan died as long as you didn't sit still long and was able to get over 20mph when moving. Ran it that way for months when I was way younger and couldn't afford a new fan!)

The temps did climb a bit to maybe 215 engine and just over 200 tranny during the extended racing game, but letting up a bit while he caught back up was enough for them to fall right back where they sit on a normal day when its all warmed up. I have a hard time believing that my truck would overheat based on its performance so far.

I get the good mileage so maybe there is a correlation to the warmer temps and the trucks that get crappy mileage. I am gonna talk to some friends and see if I can borrow a heavy load to go run up and down the Fred Hartman bridge over and over to see if my truck will get hot as it is plenty steep and long. There aren't any real hills around here other than that for me to make a useful comparison otherwise.

If it overheats I will be VERY suprised.

What is your EGR Mod?, disconnect or plug.

Disconnect, but I am going to put a plate in before the cooler to keep the system from having to cool migrating heat. There isn't any flow because the EGR is held closed by a spring, but you have to just know with 1100 or 1200 degree or even HIGHER temp exhaust gasses looming around in there that it surely places extra load on the cooling system.

I don't see how the "cooler" can be anything other than a coolant WARMER as the thermal transfer is obviously from the super hot exhaust gasses to our 200 to 210 degree water. That spread in temps is just too great. Some owners have reported a 15 degree water temp drop under load with the plate in.

One thing I have been wondering, I read about the guys that do overflow putting water back in after it cools, many on the sides of the road or at a station. If you aren't adding glycol based product back in as well then you are heading in a downward spiral because your boiling point is getting lower and lower due to the gain in water and the overall loss in coolant ratio.

I also wonder if the trucks that are getting hot are coming off the floor with a weak mix? Just a thought.......

Anyone verify that their pressure cap holds at least to advertised rating? Being new doesn't make something correct, and sometimes the $2 part ruins the $40k one.....

This and the actual coolant are often overlooked in favor of the major or expensive parts.....

That would only prevent the boiler over. The temps are getting to the boiler over point for the correct system pressure for some guys. This problem is not as simple as coolant. There is either a casting issue or something else. Too much heat.

I don't know how anyone could have verified the correct system temps and pressure at the boilover point while driving down the road because the truck isn't equipped with a pressure monitoring device, it only has the gauge and I am sure that it is far from being a precision device. The rudimentary markings on the facing tell me it was never meant to tell you the exact temperature of the motor.

Reducing the coolant content mix for sure would have a detrimental effect on your cooling system's ability to handle the heat load for a few reasons. The main one I was looking at in this case is reaching the temperature and pressure much easier than if it was correct.

It very well could be a casting issue, causing hotspots if that's what you are thinking....if that is true you should be able to see heat differences with a handheld temp measuring device.

The other thing is the EGT's with the new turbo are higher in the LLY (they hit 1400 in the last pulloff completely stock...but where was the boilover????) and the housing is still water cooled. More heat there.

Problem is not all trucks are overheating and modern castings are pretty good these days with all the computers.....that's why I was looking at the cheap parts and the human controlled mixtures.....

By the way I take issue with your larger tires only "reducing your power off the line", they are reducing it everywhere and creating a healthy load on your engine that's just a fact. Try slapping 2" or 3" taller tires on a healthy street racer and see how the power vanishes.
Edited by: TxChristopher

Water transfers more heat than coolant does. Running pure water with a "water wetter" will transfer more heat than any other option including 100% coolant.


If these guys who are overheating are reporting accurately, and not blocking airflow to the cooling system, there is certainly something wrong with their trucks that coolant ain't going to fix.


Hope GM actually researches this throughly and finds the reason.

TxChristopher


Gages may be slightly off, but not more than 10 degrees. My dealer verified my accuracy with a Tech II to be within a couple of degrees. I don't believe anyone is reporting burping before the needle is at 250 or more. That would indicate a pressure problem. Until there is vapor involved, temperature and pressure are dependant. It is great that everyone here is coming up with ideas, and believe me, the guys with the problem are interested in any ideas. I have put alot of thought into this. I truely believe that there is one of 3 things gong on with these trucks.


1. The engine, turbo and EGR are develping more heat than GM calculated.


2. There is a casting issue with a group of motors (build date on the motors may be different than the trucks). I realize that casting issues are rare now that computers are handling the layout, but it still can happen.


3. There is a problem with coolant flow.


BTW, anyone out there with cooling problems notice if either of there radiator hoses appear flattened when the motor is at operating temps? I noticed this once and had not gotten into it. I can not remember wether it was on the supply or return or both. That would tell me that some thing weird is going on with pressure. I would have expected them to be nice and fat.

BTW, bigger tires change gear ratio, therefore only can change torque available. HP or rate of work will only be affected by change in the weight, drag or rolling resistance. This just means guys with bigger tires may have to down shift earlier (lack of torque at the right speed). This does not create any heat. What issue do you take with this?

I love these discussions http://www.dieselplace.com/forum/smileys/Big Smile.gif cause I am a problem solver by nature and talking about this stuff gets the mind going. Wow so many points brought up. Gonna have to do multiple posts to properly address each one.


McRat: I agree with you that water is better at absorbing heat and transferring it, it is roughly 40% better than glycol products, and with water wetter it's capacity to absorb and transfer heat is increased slightly more. The problem is that water performs poorly as heat is applied that surpasses its boiling point, and water wetter does very little to aid in this. The reason for this is water has a high surface tension and is a tremendous creator of pressure when the heat continues to increase beyond the boiling point. By the time you reach 225 degrees with water only you have created around 20psi of pressure and by 250 degrees you have created around 30psi. Game obviously over there. Water wetter helps water very little in this way so when the heat is on they fail miserably. Glycol products increase the boiling point dramatically, pure Ethylene Glycol wont boil even under atmospheric pressure until well over 350 degrees and doesnt create 15psi until real close to 400 degrees. If we had no surface temperatures inside the engine over say 220 degrees then water would be the ticket, but we have areas that get well over that (cylinder heads, cylinder liners, turbo housings, now EGR coolers, etc) so water and water wetter just cannot get the job done.


So in effect you are right about waters ability to transfer heat.....but only up to the point that it vaporizes which is way way to low a temperature to be an effective engine coolant when alone or even with water wetter. In other words if it really generates heat then water is not an option.

LLY's do run hotter than the LB7 no question. Mine hits 220 it a heartbeat pulling a load so when you add power it gets even worse. I've tried about everything to cool truck but not much luck. Water injection has made most difference so far. Just my 2cents

my truck was getting hot and my coolant line was kinda flat started looking under the truck and there was some coolant on the block the bottom of the water pump is leaking not enough to drip on the ground but enough to be present on the block and frame rail it was not visual from the top of the motor but it might be the weak point in my cooling system it is at the dealer getting a new water pump I hope this solves my heat problem.If you look under the motor and see orange crap that looks like silicone on the block that might be where your trucks cooling system is loosing pressure

exford: I still take complete issue with the tire size and effect on torque and horsepower to the ground. A decrease of mechanical leverage by extending out the distance from the center that a rotational force is applied will always reduce the measured amout of force at the end of that arc. Larger tires are there no matter what the engine speed, gear ratio, or vehicle speed so the effect is a 100% constant and the effect is linear across the entire operating range. Horsepower and Torque are tied at the hip mathmatically, especially in our case due to the operating range we operate in. Our Horsepower is 100% dependent on our torque. Here is a statement that cannot be refuted:


It is impossible to increase horespower without increasing torque below 5252 rpm. Horsepower is 100% dependant on torque below 5252 rpm.


I find it odd that you concede that your torque is lessened but not your horsepower. I agree with you that horsepower is the rate at which work is done. The original calculation for horsepower was weight over distance versus time, how far a horse could move a certain amount of weight in a certain amount of time. It ended up being 330 pounds over 100 feet in one minute.


Horsepower is also expressed in electricty using watts, if I recall right 746 watts in one horsepower.


In our case we are dealing strictly with a rotational device, so our horsepower is derived from our torque. The only way to make horsepower is to make more torque, until you get to 5252 rpm then from that point on horsepower will forever increase as long as torque stays the same. With enough rpm you can lose torque and still gain horsepower.


Why? Because horsepower is afterall, like you said, a variable describing a rate of application. More rate, more horses.


The equation for hp is: hp = torque x rpm / 5252


Plug some numbers into that and see what happens.


Edited by: TxChristopher

exford: now that you have given me the temp numbers I am almost 100% sure it is a coolant or pressure problem. With a 50/50 proper mix of coolant and water the boiling point at 15psi is 265 degrees. With 70% coolant and 30% water you increase this to about 275 degrees. My overflow tank clearly states that it holds 15psi. You wont have the high pressures unless you have reached that boiling point, it is what creates the pressure.


If you puked at 250 degrees or even 260 degrees there can only be two possible explanations:


1) the system is not holding 15psi


2) the concentration of coolant is too low which is allowing it to boil early (lower temp) and create the pressure needed to puke.


It could be a combination of both. If thats wrong someone explain to me why.


If it isnt holding pressure or if the mixture is weak then your engine would get hotter easier and when it did it would be on the fast track to overheating.

JUST GOT REFLASHED TODAY. Dealer said not all trucks fall under the reflashing, but it made a world of difference to mine. No more pinging, more responsive and runs from 220-230 to 195ish. Definatly worth it. My service writer said it was the first one to his knowledge that they have done. And was curious were I heard about it..


THANK YOU DIESELPLACE.COM

What issues did the reflash address? Improper fueling by injectors causing high combustion temps? JJ had made a possible correlation to mileage, smoke, etc.

I asked the closest stealer to me about a reflash and they said they don't do them unless something really points to a PCM problem.

Any more info you have would be greatly appreciated!

Hey Tx, I told my dealer about the reflash and he asked me if I would mind trying it. There was no difference in eng temps, but it idles and runs smoother and quieter. It is a little more responsive. The reflash adresses rough idle, parking lot surging, turbo ping. If I were you or anyone reading this LIE (or do what they do to you) and get this done. It took my dealer 10 min to do this.

Should I take out my edge before reflash?

Gomax: yeah that's what I heard from the stealer too when I asked about the reflash. I mentioned the temp problem and they said it didn't have anything to do with that (maybe that's the marching orders they have who knows). Thing was the stealer said unless the truck has those symptoms as you described that they won't do the flash. I told him seems to me that if an update was out there that it seems they would automatically do it anytime a vehicle came in for anything. Nope. So I guess if anyone wants the flash to go and and lie and say your truck has these symptoms?

Thing is if ya don't really have those issues is it good to go against the old "why fix it if it ain't broke" addage..........the possibility exists to CREATE a problem then.

Should I take out my edge before reflash?





YES!!!!!!!!!!!!!!!!!!!!!!!!!!!!! I would or your warranty will be http://www.dieselplace.com/forum/smileys/Dead.gif

TX, The problem is getting any where near those temps, not what happens once it is there. If guys were burping at 230, then we would be looking at a coolant mixture problem. They are burping at the designed temp to burp. Whatever is the problem is getting the system to that temp. I agree, water or even the proper mixture could spot boil at any extremely hot surface, such as the turbo or EGR. We have talked about that. This would cause cavitation if it did not liquify by the time it got back to the pump. I still think that might be part of it. There is just too much heat being generated.


You are absolutely correct in your equations. HP is a function of torque. Answer this, what are the pieces in your conservation of energy equation. I said the torque would be available at a different rpm. Your available torque and horsepower are just at different rpms -- see your equation. Steady state driving (not take off), maintaining a speed, work is how much energy is needed to overcome the opposing forces. Larger diameter tires do not play into that, except any rolling resistance change, only in the moment of inertia. Increasing speed, or acceleration would change. The original debate was if larger tires increased heat load. I say only on acceleration, not maintaining speed. The easy fix is to simply change gear ratios.

TX and Exford, hats off for sticking to the facts and great dialogue. Most of what you guys are saying is over my head, but so long as we're sticking to the issue at hand and making progress I'm happy.http://www.dieselplace.com/forum/smileys/Clap.gif


Couple of questions/comments: Is the LLY engine block a totally new design from the LB7? I thought they were the same block and heads, just the injectors were moved externally, the new variable ratio turbo, and some other minor improvements. The LB7's in service in California and the Northeast have operated with EGR's and CAT's for several years with no overheating issues. IMHO this kinda puts a questions mark for the EGR causing the overheating.


I disconnected the EGR for a few weeks, then towed the 5ver to 500 miles, then reconnected it for the trip back with no difference in engine temps. Actually thought the grade braking worked better with it reconnected.http://www.dieselplace.com/forum/smileys/Wacko.gif


The possibility of some LLY's overfueling is one idea I haven't seen anyone explore or refute. Is there a way to nail this down, say like putting a probe in the exhaust to analyze excess fuel or something like that? Would like your opinions on this? JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

I had my reflash done today. I did not notice any improvement in performance, mileage, or temps. I put 30 miles without the 5er and 40 miles with the trailer.

The dealer installed a “data collector” with a hand held switch to activate the recorder when truck acted up or got hot.

I hooked up the 5er, not fully loaded though, and went up the 5 Fwy north of Castaic Junction for a climb. This was not the hill that gave me trouble, but a formidable hill. The outside temps were about 96 degrees, the hill is about 5 miles long, with less than a 5% grade, rising to an altitude of about 4,000 feet. The hill that gave me the “CAUTION ENGINE COLLANT HOT” and a 250 degree engine temp and 240 trans temp was the southbound side on the other side of the mountain (the infamous “Grapevine”). The "Grapevine" is about a 6% grade, shorter in distance, starts out at a lower altitude and rises to about 5,000 feet.

I did not feel like driving another 40 miles just to go back up that hill. On the “lesser” hill, I did record engine temps in excess of 240, and trans temp in excess of 230. This is too hot IMHO.

Other than this cooling issue, I love this truck! I don’t want a new one, and certainly not another brand, I just want it fixed. The tech that worked on my truck mentioned that he had seen some of the new 2005 gas HD’s and noticed they now have two electric cooling fans instead of a clutch fan. Has anyone bought or seen a ’05 Duramax HD? Do they have electric or clutch fans?

After I return the recorder early next week, my next call is to Lemon Law Attorney John Mcque. I already spoke with him once. John seems to be a very nice person and extremely knowledgeable attorney. I hope he can get GM to listen and find a repair for our trucks.Edited by: cadent45

Cadent45, today I saw a new 05 and it does not have electric fans. Take this for what it is worth. The dealer told me the way they are staying cool is taller hood and more open grill space.

exford: the burping is not dependent on temperature. The only thing that causes burping is pressure period. It would burp when it gets past 15psi whether the temp was 100, 250, 500 or any other number.

The expansion tank handles the liquid expansion volume caused by the heating. The cap controls system pressure. Those are hard set factors that do NOT change.

The pressure only comes when you boil the coolant mixture. I am not talking about at a specific hot spot because that will return to liquid quickly when it moves away. The water pump creates a small amout and so does the thermal expansion but by far and away the boiling brings in the pressure. So until you boil the coolant you won't have much pressure and surely not anywhere near enough to burp.

The boiling point of a proper 50/50 mixture of water and coolant is 265 degrees at 15psi. Those are set numbers as well, they do not change.

So please explain to me how you can possibly burp at 250 degrees......there are only two possibilities and they are the system is not holding 15psi or the coolant is weak (too much water) and is boiling early, or a combination of both.

Even at 260 you are still in the good to not burp it.

If I was burping at those temps I would have the stealer pressure test extensively (including the cap on the expansion tank) to be SURE my system holds 15psi "like a rock" and also drain and fill my system with a 50/50 mix (60 coolant/40 water would be even better)

Do not tie this to WHERE the heat load is coming from. I am focusing on the proper response from the cooling system and until it performs correctly there is no base to begin finding the problem.

I am gonna get to your heat source on my next post.......

Pressure and temperature are directly related. I agree, burping at 250 means a problem, but I meant higher than 250. What I am trying to say is that unless there is a flow problem, coolant is not the problem. Some thing else is getting the coolant past 210. JJ's idea about messed up thermostats might have something to it. The whole issue here is why some new trucks are seeing 230 or greater while previous LB7's never budged the gage. There is definately heat generating changes made to the entire system. Blocking the EGR does not seem to solve the problem. Maybe it is something with the VVT, 3rd injection pulse. I really think the only way this is going to be solved is by GM stepping up, taking a problem truck and analyzing it. They know what is supposed to be going on. Bad part about that is if they might have already figured it out and found that the repair is to expensive to address so they plan to blow everyone off.

Ok. It only took reading the various threads about this overheating topic a good five times each to come to some workable conclusions. Before I get to that I wanna hit this tire issue one last time.


I cannot stress to you guys enough how much power you are tossing out the window with the big azz tires. I street raced for 15 years very successfully, enough to make it into magazines, and I can tell you that adding a tire two inches taller really knocks the hell out of the power, and you guys are going well well beyond 2 inches. I once went from a 26 inch tall street tire to a 28 inch tall slick looking for more traction, my 60 foot time fell by a solid tenth but the car was four tenths slower and a few mph slower at the quarter. Tried several runs with the same effect and finally went to the pit and changed back to the street tires and the ET's dropped back to normal. The math showed about a 40 horsepower loss from the tire change.


Exford, I know you are gonna say otherwise, and I am not so sure that you really arent sure yourself as much as you are just quoting fingers on the tire issue. The things you have been posting are practically word for word what fingers says on the tire issue. Yes the power from the engine is still the same but the losses in your drivetrain are eating you alive. If you dont think resistance at the wheels can sap your power try towing with the parking brake dragging. I am in the process of getting a gtech pro rr and a set of 315's so I can show you the dramatic power loss to the ground you are incurring. I wouldnt be suprised if it is on the order of 40 or 50 horsepower and probably more. Imagine trying to tow the weights you guys are towing with only 260 or 270 horsepower (and thats peak, everywhere else horsepower will be far lower as well). Do the math on your torque losses at low rpm to be at that low of horsepower and you will crap. May as well be trying to tow that monster weight in a one ton gasser 5.3 liter. The stress (load) from your bigger tires is coming back to nail your alli and thats a point I am gonna get to after this. I find it more than a coincidence that exford, fingers, and cadent44 all tow big, all overheat, and all have the big tires.


quoting cadent44: "The only change I made to the truck is the wheels and tires, they are H2 wheels and tires, (315-70x17),
but that should not change anything, right?"


cadent44 dont let these guys fool you, try putting the stockers back on and go after that same hill, drive it reasonably and tell us what happens.


I am gonna leave the tire issue until I have the gtech to back me up, and I know it will. I could do the math on the actual forces but I dont want to spend hours calculating vectors and rotational mass and effective gear ratios at a billion different rpm's.





So now on to the next thing I have noticed. Nobody is gonna like this one I think, but it seems to ring true with the trucks that are overheating. It may be a factor in the poor mpg trucks as well.


First some quotes from this thread and another about the overheating:


OLD RIVER: "Truck temp crawled up to 250 with "engine coolant hot" light on at 45 mph. Transmission got to about 240"


cadent44: "On the “lesser” hill, I did record engine temps in excess of 240, and trans temp in excess of 230. This is too hot IMHO


socal LLy: "just got the call from the dealer they could not find anything wrong with my truck 7mpg and over heated trans and motor"


huntsalot: "Driveing today flat ground 89 outside and trans goes over 200 and temp goes over 210"


cadent44: [i]"The hill that gave me the “CAUTION ENGINE COLLANT HOT” and a 250 degree engine temp and 240 trans t

Thing that stands out to me and I cant believe I didnt see before are those transmission temps. We have been focusing all over the LLY having a cooling problem but even if it does explain to me those high transmission temps????? The two DO NOT share a cooling system, so your engine should be able to overheat to its hearts content and the alli should be at a normal temp.

Not exactly true. The transmission fluid goes from the transmission to the passenger side of the radiator where there is a water/oil cooler. It then goes to the front of the radiator stack for the air cooler. So if you got high transmission temps your heating the cooled water that goes to the engine.

Otherwise I think your noticing something about trucks that overheat. Bet no one will put their stock tires back on and try the hills again.

Jim

I have the 2 LLY's overheating. Stock tires and have not noticed any tranny heat problems. Overheated yesterday in Montana in 58 degree weather with a total 18,000 pounds gross.

My tires are stock. 3500 SRW comes with 265's, not big in my opinion. Sufficient is what I call them. I'll back off on the tire size thing, but I am not quoting fingers. Last time, rolling resistance is the only thing that changes. Not quite like riding the emergency brake, but it will affect it because typically larger tires are wider and more agressive tread, not to mention a different rubber composition.


One of the reasons why I traded in my Ford was my tranny temps were too high. Didn't seem to affect the engine temps on that one. Check out this, courtesy of Russmonster. Now what. My tranny temps rarely get over 200 and I run in TH as soon as I hook up. One time out of a fuel station I forget to put it back on. Flat land by Tucson, trans temp went 215, engine temp 205 (normal). As soon as I put TH back on, all was good.


Maybe you are on to something, if all I need is the dealer to replace my tires with the dinky ones that they put on the 2500's, I would be thrilled. They are load range E at least.


If I was quoting fingers, I would have mentioned how his driving habbits compensate for his big tires. Keep the RPM's up.


In the picture, he is out of TH, but he states the reason was so that it would cool back down. I didn't go along with that, but it was him having to pull over, not me.


Since my tires are stock, wouldn't you say that GM would have changed the programming to compensate for shift points and such?





http://dieselplace.com/forum/uploads/947_dash.jpg

I believe our problem is in the radiator and the main source of heat is coming from the LLY. With mine it is always the engine temp that begins first. After extended time of high heat in the radiator the transmission fluid will eventually reach the same temperature as the motor. With that much heat over load on the radiator it will not recover until the load is taking off the motor, or in our case, we reach the top of the hill. Once the transmission fluid is that hot it takes a long time to cool it back down. My truck is 100% stock and will not be changed until a fix is found. It is a 3500 single rear wheel 4x4 crew long bed with every tow option that GM has to offer and should pull my 36' 15000lb 5th wheel over any major grade in North America with "No" problems. I think you guys are doing great and with strength in numbers we will find the problem... Which is "GM".

Quick posts, the hurricane keeps knocking our power out. Guys are overheating with stock tires, tranny utilizes the radiator to both heat/cool fluid. Not all LLY's are overheating so inherent design flaw very questionable.


Thermostats are very big player in the engines ability to dissipate heat. Inadequate airflow across the radiator, thermostats installed improperly, or a combination of both very suspect! LLY's overfueling is another potential heat generator! How do we narrow these down?


Couple of guys have had their thermostats changed out by the dealer, but I have to tell you the techs may not be aware of just how critical it is to "get them right"! More to come, but posting to avoid losing with power failure. JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

How do we narrow these down? We need for the guys with the overheating LLY's to "take the bull by the horns". Basics first, make sure you have all maintenance issues addressed. By this I mean new or fairly new engine oil, clean air filter, proper coolant mixture, tire pressures up to max, etc.


Then, one of you guys that are mechanically inclined need to change out both thermostats, paying careful attention to put them in their proper location. Afterwards if you can pull a heavy load and report the results. If that doesn't do it, on to overfueling? That's way out of my league!


One more thought! Am I recalling correctly no LLY's are overheating without a load on them? Help me out here if I'm wrong guys! If true, what changes might the PCM make to fuel pressure, timing, etc., to sustain vehicle speed, hp and torque when towing? Anyone know of any compensations the PCM will make when towing? JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

Seems I missed the line sneaking into the tranny and back out to the cooler, it was early twilight when I crawled under there to look, so my bad. Also exford I thought the way you defended the tires you had them as well. Sorry about that.


I agree JJ that the guys with the hot trucks need to define overheating, as in engine temps and tranny temps, outside temps, grades and the speeds they were attempting to hold. They also need to tell what mods and if the truck was in T/H or not.


Towing without the T/H active will have you without a locked converter which will be making heat like a mofo under big loads (aka lotsa weights steep hill) and now that I see the alli and the LLY share some cooling that could be an issue.


Still collecting data, either way my alli cooler is gonna be moved away from the front of everything. Maybe it will help lower the occurence of that clutch fan coming on as well. The passing through the radiator of the alli lines is also suspect, I dont like my big heatsink tranny palming off its heat to my cooling system. More than a few racers have eliminated the tranny cooler lines and not had a problem with the trannies warming up.

Boy am I glad that I've found this place!! Misery loves company I guess.


I bought a 2004.5 lly 3500 drw to pull my 5er and I can't get out of the valley I live in with out overheating! I am bone stock with 2800 miles waited till I had 1500 miles before I pulled anything. Best milage average on the DIC is 13.0 mpg. This is my first deisel so I am dissapointed to say the least.


5er and truck weigh 20,700 so I am not overloading this according to GM. Talked to Dealer He says one other person has also compained about this.


Sure am hoping we, they, you guys figure this out I love this truck when it's not pulling up hills

Wallbanger: welcome to the forum, sorry you are having problems.

Do you have any details? Sure would help. Such as:

Normal engine temp (truck warmed up)
Normal tranny temp (truck warmed up)

When overheating happened:

Engine temp
Tranny temp
Outside temp
Tow/haul on or off
Weight of load
Percent grade being climbed
Speed you were attempting to maintain

Details details......more information is needed to begin to try to figure out what this problem may be.

[QUOTE=exford]

My tires are stock.* 3500 SRW comes with 265's, not big in my opinion.* Sufficient is what I call them.* I'll back off on the tire size thing, but I am not quoting fingers.* Last time, rolling resistance is the only thing that changes.* Not quite like riding the emergency brake, but it will affect it because typically larger tires are wider and more agressive tread, not to mention a different rubber composition.


One of the reasons why I traded in my Ford was my tranny temps were too high.* Didn't seem to affect the engine temps on that one.* Check out this, courtesy of Russmonster.* Now what.* My tranny temps rarely get over 200 and I run in TH as soon as I hook up.* One time out of a fuel station I forget to put it back on.* Flat land by Tucson, trans temp went 215, engine temp 205 (normal).* As soon as I put TH back on, all was good.


Maybe you are on to something, if all I need is the dealer to replace my tires with the dinky ones that they put on the 2500's, I would be thrilled.* They are load range E at least.


If I was quoting fingers, I would have mentioned how his driving habbits compensate for his big tires.* Keep the RPM's up.


In the picture, he is out of TH, but he states the reason was so that it would cool back down.* I didn't go along with that, but it was him having to pull over, not me.


Since my tires are stock, wouldn't you say that GM would have changed the programming to compensate for shift points and such?_____________________________________________ __________

Did anyone previously mention or notice that the tranny is not overheated in this photo?Edited by: cadent45

Thanks TX glad to be hear.


normal water temp stock gages 205


trans temp normal around town 190


pulling 5er at 13,500 up a 4mile 5% to 6% grade try to maintain 2000 to 2200 rpm water temp red line with dic engine overheat. tranny also climbs rightbehind engine temp to 250 and yes I had stealer change tranny fluid. outside temps do not matter. has happened at 62* and 104*. Always pull with T/H on. as far as speed goes worry more about keeping rpm's up for cooling but start out at 65 mph and top out at about 30mph

Oh believe me exford, I noticed that first time I saw it, and it is really the damn wrench in the cogs because mostly everyone says the tranny temp follows the engine temp when the overheat happens. I have been unable to account for yours at all.....was that taken on the fly or after pulled over? I am glad you asked this because the exact circumstances of that pic have been bothering me for a while now. I was kinda thinking you had stopped and the tranny had perhaps coooled some.......

Only you know. Spill it!
Edited by: TxChristopher

I just got back from a trip to Big Bear Lake. I went up the “back way”, Highway 18 via Lucerne Valley. For those of you that know the area, I’m sure you’ll agree this is quite a nasty hill. For those that do not know, it starts out on the desert floor (about 2.500 +/- feet), and climbs to Big Bear Lake (about 6,500 +/- feet). The last 2,500 feet of the climb is an 11% grade with three hairpin switch backs. Pretty tough stuff!

I made this trip to get a final recording on the data recorder the dealer installed last Friday. While climbing the area of the 11% grade, my engine temp immediately went to 250, the DIC came on and stated “Engine Coolant Hot” and the tranny also reached 250 towards the end of the climb. I was forced to turn off the a/c and turn the heat on to 90 with the fan on full speed to keep it from boiling over. There is no place to pull over and stop, so I did not want to risk getting stuck. Outside temps started out at 95 degrees and decreased to 80 degrees at the top of the hill. I never let the rpm’s drop below 2,200 and never got near 3,000. This situation is not acceptable!

Several years ago I climbed the same hill with 33’ Bounder Motorhome with a Ford 460 motor, and a 26’ Four Winns Cuddy Cabin boat with an i/o V-8 motor behind the Motorhome. The 16k lbs. Motorhome and 6k lbs. boat, never overheated, no rise in temps. Yes a climb in such a combo was not the smartest thing to do, but it made up and down the mountain.

First of all, I always, yes always tow in TH, no exceptions.

Secondly, it is always the engine that heats up first and is also first to cool down. When the trans gets hot, it always stays hotter longer.

Third, no overheating issues unless I am towing, and my trailer is no where near the maximum weight capacity.

Lastly, overheating occurs when out side temps are over 90 degrees.

And yes I am aware that larger tires affect initial take off, but they do not noticeably reduce my power output once I am rolling.

I’ll update this post later this week after the dealer analyzes the info on the data recorder.

TX, picture is not me, read the other thread and you will get the details. I have never got to this point. I couldn't help but back off before I got to that point.


Notice most of these are in the SW with big hills. When I back off and turn off AC, the temps don't recover, but don't rise anymore than 240 or so. I really think that lack of power should slow me down on a hill not temps.

Yeah I figured out the russmonster thing, and I mistook cadents post for yours a couple back (driving down the road reading posts)


I am with you, you would think that lack of power would slow you down, not temps. And turning off the AC is ridiculous.


If the trucks were being held at redline then that would be a different story since that would be imposing all the big frictional losses etc etc etc but that isnt the case. I am quickly coming to a dead end here and it is frustrating. Your overheating problems are consistant with a cracked block or head type problem, light loads hide it but heavy use brings it right out.


I havent been able to get with my friend to see about dragging a heavy trailer, I really wanna see if my truck gets hot too. I would hope it doesnt but it just might.


Its been so long since I went thru the overheat problems I am having a hard time recalling some of the things we discovered. The flat hose thing bothers me, isnt that a thermostat cycling problem?


I need to do more research...........


*On edit: I keep thinking we used to get the lower hose to flatten when a block was emptied of water, and after adding water the cool water would hit the thermostat and cause it to briefly or partially close, which would then cause suction from the water pump to collapse the hose. Either way the hose flattening is an indication of a flow problem, as in blockage, it is NOT a good sign at all and the root cause of it MUST be determined. Maybe there was casting crap or sealant pieces or some other foreign material that is plugging the radiators of these overheating trucks, not totally blocking the flow but restricing it enough that when the heat is on from towing you dont have the reserves you need to survive.


Another possibility, has the hose supplier or part# changed? An inferior part could be collapsing under higher engine speeds as the water pump suction increases. Hmmmmmmm didnt someone post something about a new water pump that flows more on the LLY?????? Maybe the new pump is capable of sucking more than the hose, which might have and probably did stay the same, can withstand, and it partially or totally collapses and restricts flow.


Anyone willing to try replacing the lower hose with maybe one of those generic spring filled hoses like they sell at autozone and then go towing to see what happens?


*On second edit: I went outside and crawled under the truck, it takes like NO pressure at all to press the lower hose flat with your hand, there is NO anti collapse spring or ribbing or anything and the hose material is VERY soft......maybe there is something there guys......the new water pump may have enough suction to flatten it and restrict flow and unless you were putting the big strain (towing) you might never know? Just a theory......dont bash me for this!





Edited by: TxChristopher

just got my truck from the dealer it got a new water pump and steal getting hot and now the belt sounds worse then ever and was looking under the hood and noticed that the upper radiator hose was flat as a pancake and low coolant light on the dash back to the dealer tomorrow

So maybe the new pump has enough output pressure and suction that it is capable of flattening one or both hoses. Too much pressure drop across the thermostat perhaps? That hose being flat is the key. I wonder if I tie my truck to a immoveable object with my 30,000 lb tow strap and stall it up to 2000 an hold it there if I can simulate this........should warm it right up, would be a helluva load and airflow would be nil and I could have the hood open to see if the hoses crap out or not.....

Might not be able to though because you guys are hitting higher rpms where the pump would be flowing a LOT more and also where it would have more suction and pressure output.

Socal.......try replacing that hose with one of those ribbed hoses that has the metal wire to prevent collapse in it. They sell them at autozone, sorta a generic hose for when you have a one off, like a TriumphTR7 with a chevy 350 in it :)

You can always go back to stock if it doesn't work. It would be worth a try I think.

Once that hose flattens the flow is pinched off and you WILL overheat, there is no way around it!

TX,
possibly you are on the right track. Reading all these posts I am thinking since a while that the LLY might be not the main reason for the overheating problem. Too little has changed between the 2 engines to cause that kind of problem.
Maybe just simple things have changed together with the LLY like a different radiator hose, different water pump, different connector at the radiator or different thermostats. Maybe its also a cracked exhaust manifold because of the new turbo charger...
The picture with the hot as hell engine and cold tranny makes no sense to me at all.

Same thing I was thinking, not a huge change in design really, the EGR was on LB7 trucks in california and you don't hear them complaining about them.

That higher output water pump is a new animal though, and the way these guys are describing the sudden quick temp climbs fits my idea about it pinching the hose or hoses off from too much suction combined with too much output. Think about how fast your temps would climb if the water were STOPPED suddenly.

It has been a zillion years, I had a TR7 that did that (discussed it in previous post start of this thread) and solved it with the hose I am describing.

I would try the hose, or maybe even get the stealer to put an LB7 pump on my LLY, one of these dealerships that have been having to do endless work on one of these trucks might be willing to try that. The hose may solve it though.

That way the picture from Russmonster truck would all make sense suddenly. Rapid rising engine temp, boilover and burping because the coolant hose is flat (sudden increase in pressure). The tranny has its own pump so it takes a while to get hot from the hot water in the radiator so its still cool while the engine is boiling...
time so sleep.....finally

I have also noticed the flat hoses on my trucks!

I am thinking it may follow its way back to the bottom hose, I cant believe there is no anti flatten spring in it. As it stands now I would be looking to replace entire hoses or major sections with wire reinforced hoses that cannot collapse. This is not rocket science. The dealer may and should be able to help you with this.......run the idea by them that the hoses are being sucked flat by the suction of the new high volume water pump on the LLY. Seems that pump has the suction to pull down even the top hose across the radiator core, which is possible.


Thermostat flow may be too little for the new pump and causing the pressure drop is also a big concern, its tougher for the top hose to get flattened but with "blockage" aka too small of a thermostat opening in front of it, you would see the upper hose get sucked down......


I would say #1 priority.....new or larger flowing thermostat.....if not possible new or larger flowing bypass around the thermostat and the addition of wire reinforced hoses that will not crush. The hoses by themselves may solve this problem though.







*On edit: Reading back through posts yet again, seems that guys can back off and avoid the overheat....seems to fit right with this diagnosis since backing off would slow the gear driven pump and possibly relieve the pressure problem.....

Also, the GM info specifically mentions the front thermostat acts as a RESTRICTION to the cooling system, creating a pressure drop! Dollar to a donut says the drop with the new pump is too great and it is causing head pressure and big suction .....more food for thought......
Edited by: TxChristopher

Someone in a warm climate could substantiate the suspected thermostat problem by removing one or the other or both and then test again. No flat hoses or overheat condition and the trouble is isolated. I know this is common sense, just wanted to throw in my 2 cents.

I thought of the thermostat removal too, but it raises pump cavitation issues as it also serves as a restriction to prevent cavitation.

I was trying to go for the long term fix by going with the LB7 pump, hoses that are wire reinforced, or a thermostat with slightly less restriction or more bypass around the thermostat to reduce the pressure drop.

Socal could get the stealer to put the LB7 pump on and test his truck.....the thermo removal he could do at home I doubt the stealer would go along with that.

Good suggestion though, keep the ideas coming!

*On edit: I am favoring the reinforced hoses though as I would prefer to keep the higher flow from the new pump, as well as the higher pressure inside the engine which raises my ultimate coolant boiling point quite handily!



Also the hoses are an easy fix....


Edited by: TxChristopher

Perhaps I should have been more clear. I was just suggesting removing them to isolate the trouble. If removing the thermostats seems to help or corrects the problem entirely, then it would seem that the problem is with the thermostats and that, at least to me, seems like a problem for GM.


I should think it would be best to remove them one at a time and test each configuration to better isolate it. In other words, remove one and make a test run. Replace the t-stat and remove the other and make a run. Then remove them both and make a run. It may not require removing both to isolate the source of the problem, but it may help GM to know what the results are.


I agree that removing the thermostats should not be considered a permanent fix, but it sure seems like an easy way to confirm or eliminate them as a potential problem point.


The reinforced hose may end up being a permanent fix, (I like the idea!http://www.dieselplace.com/forum/smileys/Big Smile.gif) but if the problem is actually a restiction in the thermostats, then the hose may mask the problem slightly but still not fully correct it. Either way, a non-collapsible hose sounds like a good idea.


I had a problem in an S-10 with a thermostat that would open half way. Normal driving seemed okay, but hit the interstate and gun it and watch out! Not really a fair comparison, but if you will consider that normal driving produced steady, although somewhat elevated temps, and heavy footed run & gun produced extremely elevated temps for short periods hopefully, you can see some possible simularities. I replaced the t-stat after it cooked my radiator and realized what it should have looked like all along. Towed my boat around with it and the temp never budged again.

Nah man, you were clear the first time. I wasn't knocking what you were saying at all. My truck doesn't overheat, I don't tow big like these guys so I haven't run into this problem personally. I agree with you on the test of removing the thermostat. As far as it being a restriction, it is designed by GM to be a restriction to prevent water pump cavitation. I just don't think they factored in the huge rise in pressure before and after the thermostat causing the pressure drop. You can imagine the rock and a hard place you are in once that hose is flat.

I agree with everything you are saying just trying to point out the part about the thermostat being an INTENTIONAL restriction.

I find it ironic that I went thru nearly this exact same stuff about 15 years ago when I built my TR7 with the chevy drivetrain. I went thru griffin radiators, high flow robert shaw thermostats, a crapload of electric fan combos, mega flow high volume water pumps, and then reinforced hoses to stop hose collapse. I had mostly forgotten all that stuff until someone posted the hose flattening issue and it made me think back to my troubles with that car.

Keep the ideas coming!
Edited by: TxChristopher

I just thought maybe I wasn't clear. I do tend to leave out important details from time to time. Since I understand what I mean, I figure everyone else must too! http://www.dieselplace.com/forum/smileys/HiHi.gif Its a flaw I'm guilty of having.


Mine doesn't overheat either. I even went out this weekend and towed the 4wheelers around to see if I suffered from this problem. Couldn't duplicate it. Ran the air too. I know the 4wheelers are nowhere near the weight some of these guys are haulin' but I have a 6" lift with 315/75R16s so I figured even with low tow weight I still might be a good candidate for overheating issues. Of course, I did change my diff gears to 4.10 after the lift to get my final drive back up. Its still low at 3.62, but nobody makes a 4.23 to put me back to 3.73 so I had to settle. Around here (Wyoming) I have some nice elevation changes to test with and some pretty long steep climbs with switchbacks and such.


I guess I should be thankful I'm not suffering from overheating. At least not yet anyway.


Love the forum. Thanks to everyone for all the great info!

I know exactly what you mean on trying to duplicate this. Thing is, its hard for us to impose the biggest baddest heat load without pulling the 15, 18, or even 20k these guys are. Even then there will be a lot of uncontrollable variables we can't duplicate like vehicle speed, engine rpm, wind resistance, etc etc etc. Some hoses might have a weak spot in them, some trucks might produce an extra lb of suction more some thermostats might be slightly more or less restrictive......the variables are tough here and that's what has made this a biatch!

I keep waiting for one of the overheating truck owners to come back with test results. I want my theory to play out so that GM can issue a TSB or even better a recall so that NO duramax is embarrassed on a hill again and even more important no owner left stranded or right next to it again!

*On edit: hope this is the solution, I know wifey is getting tired of me waking up late and looking up things and generally spending a LOT of time on this, also crawling all over and under the truck with a flashlight.....I am sure she thinks something is wrong with our truck by now!

Edited by: TxChristopher

Be careful now, don't wanna pi** off the boss!http://www.dieselplace.com/forum/smileys/HiHi.gif

Welcome to the dog house boys! My wife has been bitchin, eerrr I mean complaining, that all I do is spend evenings on this site. Dang if she ain't right! http://www.dieselplace.com/forum/smileys/HiHi.gif


First I've heard of the flat hoses! http://www.dieselplace.com/forum/smileys/Geek.gif Sure would seem to inhibit coolant flow and create significant backpressure. This should be simple to run to ground. I'll PM RickDLance, Fingers, Russmonster and a couple of the guys with overheating LLY's to see if any of them can change out their hoses with the wired ones. A $20 fix works for me! http://www.dieselplace.com/forum/smileys/Embarrased.gif JJ

One additional thought! As the coolant temperature heats up the hoses get hotter and more pliable. The combination of the heat buildup coupled with an abrupt increase in backpressure could collapse the hose. Hope that makes sense!


Sure am glad that hurry cane got the heck out of here and my power is back on. WWWWWWWWWEEEEEEEEHHHHHHHHHHHH! JJ http://www.dieselplace.com/forum/smileys/HiHi.gif

I've PM'd all the above except Fingers, I'll do that in a few. Mama JJ took our 5ver up to GA to get out of the hurricanes path. She'll be back tomorrow. I don't mind changing my hoses out even though I haven't overheated. Highest temps I have seen are 230*, fan kicks in like a mother and temps drop. But I will be able to tell if the temps don't climb at all.


Hopefully one of the guys with an overheating LLY will try this first, that will give us our best results. JJ

Hey JJ, good to see you didnt get blown away there in the great "Hurricane State"!!!


The flat hose thing was easy to miss, nobody was reporting it and I think it was only mentioned one time in that other long thread about overheating. May have been exford. Once I started theorizing about it suddenly all the overheating guys say that their trucks do it. I think we are well on the right track now.


When you get your truck back pop the hood, that top hose is so pliable, that straight section betwen the two bends already is oval shaped just sitting there cold, when coolant first gets into it it is all wobbly. You can easily press it shut with two fingers, I am talking no pressure at all. It would take only a small amount of suction from that newly improved water pump to flatten that baby out, imagine after the engine is goin hot like 220-230 from a load what the pressure must be in front of that stat when combined with the water pump output.....a safe bet is a good bit of water gets "stacked" behind it then the pressure drops across the stat and the pump sucks the hose flat because it is pulling water in like a beast. Quick path to overheat is what you are on then, as in when these guys been saying the temps quickly rise up.


The bottom hose would be suspect as well, I am very suprised it doesnt have a spring in it. It is far larger than the top one but still very soft.


Anyway I hope this is the solution to the problem.....I am assuming you went back and read all the stuff posted while you were out playing in the stormhttp://www.dieselplace.com/forum/smileys/Cool.gif

Could this just be a bad batch of hoses? Most Dmax's obviously don't overheat. I don't have the overheating problem (yet) and hope this proves to be the answer.


Simple way would be to replace the hose with an aftermarket item and give it a test.





Rob

I have only noticed the flat hose after I shut it off. I assumed that was a result of shutting it off. Has anyone observed this with the truck running? I will be very dissapointed if some Six Sigma Blackbelt bean counting geek decided to save a couple of cents on my radiator hoses. Your alright TX. I hope this is the fix. GM would owe you and whoever proves it in a test at least a new truck. They send out a few heavy duty replacements and all is good.

Top hose: PN 15198345 SABO Made In Brazil.


Bottom hose cant read, but seems very long but fairly stout. My truck is cold right now and the top hose is flat.

I am not guaranteeing this is the ultimate problem, I was working off the assumption the hoses were flat when running. If they are then we are all over this thing. We need the guys that have seen this to report in.

I stalled my truck up against the alli yesterday, held it like that until the tranny hit 230 almost 240 degrees. The engine never even hit 210. I was hoping to get it hot then rev it up higher to see if the pump could suck down the hose but I couldn't get the truck hot with this method even after over 10 minutes of 2000 to 2500 rpm against the brakes. I guess it was worth a try even though wifey was just standing there shaking her head! The best part though was after I got the truck as warmed up as I could and then got her to get in and powerbrake it up so I could monitor under the hood, it was great seeing her face when the tires kept breaking all loose in back while I was yelling "take it higher!!!"

Did disprove my theory of the alli temp affecting the truck though :)
The LLY was totally unmoved by the alli temperature even though we know that hot fluid was passing thru the radiator and the cooler in front was radiating plenty of heat. We went ahead and went to dinner then, it took the alli a good 30 minutes to cool down while driving til it finally settled at 180. The tranny cooler is definitly inadequate.

It appears the only way to truly replicate the overheating is to slap some serious weight behind it and tackle some serious grades. I have heard back from a couple of the guys with overheating LLY's, hopefully one of them will try this mod asap and post results.


Here's JJ's hypothesis (no laughing pleasehttp://www.dieselplace.com/forum/smileys/hihi.gif) of what may be happening!


Talking through my significant climbs when towing heavy, tow/haul engaged, I'll start pushing the accelerator to gain speed and up the RPM's before I hit the big climbs. Once the climb begins I will downshift to keep speed and RPM's up, somewhere between 2200-2700 in most cases. Engine temps will begin to climb moments after the climb begins, fan will start roaring. Remember, there is tremendous strain being exerted on just about every component of the drivetrain during this evolution. Lots of heat is being generated under the hood!


As my RPM's stay high the water pump is moving coolant faster throughout the system, both thermostats should open to allow maximum dissipation of heat in the coolant, I now have significant heat and pressure building throughout the coolant system. THEN?


It appears that once temperatures get hot enough the combination of heat, pliability of the hoses, and tremendous suction being generated by the water pump may be collapsing the hoses to the radiator thereby severely restricting coolant flow and causing backpressure throughout the system. The coolant can't dissipate heat fast enough through the radiator to avoid overheating.


I have never reached the overheating point on my LLY, but 230* is easy to hit when pulling significant grades. I suspect that I just haven't hit the "wrong" climb under the "right" conditions? http://www.dieselplace.com/forum/smileys/smiley5.gif


It appears that a sustained climb of significant grades in high outside temps is the "wrong" combination for the LLY's. Personally, I still haven't ruled out the overfueling possibility. Collapsing hoses only happens when running very hot, the bad mpg's and no smoke issues wouldn't appear to coincide with the hose issues, but would certainly generate a lot of excess heat. http://www.dieselplace.com/forum/smileys/smiley23.gif


Anyone had a chance to shop around for the hoses with the springs in them. I have heard back from several of the guys with overheating LLY's, sure would be nice to have one of them change them out, pull heavy again to see what happens. http://www.dieselplace.com/forum/smileys/smiley32.gif Good input from all! JJ http://www.dieselplace.com/forum/smileys/smiley2.gif

JJ, is your hose flat when your truck is cold? Have you checked it running at temp? I don't drive mine daily, so I have to wait to check this. If it is flat cold, that could be normal. Water cooling back down and pressures dropping, but if it is flat while running at temp, this is bad and probably a major factor in temps climbing. I have a freind with a LB7, I am meeting him for lunch. I will get him to pop his hood and look at what he has for a hose and if it is flat.

While you are at it check the lower hose as well, see if it is the same. It is far more common for a lower hose to collapse than an upper. My lower hose is larger, but very soft coming out of the bottom of the radiator before it gets to that "tee". I was very suprised there was no anti-collapse spring in it.

All this theory is riding on the new high flow pump on the LLY creating pressures/suctions that on the same old LB7 system that GM didn't account for. Its the only glaring difference in the two cooling systems that I can find, especially since the EGR block has been tried and not proven to eliminate the problem.

I haven't experienced the overheating so I haven't checked them hot or cold. Mama JJ is on her way home from GA with the 5ver today. Just talked to her, engine temps 205*, tranny 190*. I'll check the hoses while warm and again in the morning and advise. http://www.dieselplace.com/forum/smileys/smiley23.gif


It is common DP knowledge that when it comes to "meck-anickel" stuff ole JJ is one brick shy of a full load. http://www.dieselplace.com/forum/smileys/hihi.gif But I have to think that flat hoses at any temp range, cold or hot, ain't a good thing! Even the hoses with springs in them still expand with high temps, but they cannot flatten. If the hoses are being sucked flat isn't there considerable backpressure being exerted on the system? Too much IMHO.


Hopefully RickDLance can change his out today, pull heavy grade and advise. http://www.dieselplace.com/forum/smileys/smiley32.gif JJ

exford: While you are at it check the lower hose as well, see if it is the same on the LB7. It is far more common for a lower hose to collapse than an upper. My lower hose is larger than the upper, but very soft coming out of the bottom of the radiator before it gets to that "tee". I was very suprised there was no anti-collapse spring in it.

All this theory is riding on the new high flow pump on the LLY creating pressures/suctions on the otherwise same old LB7 system, that GM didn't account for. Its the only glaring difference in the two cooling systems that I can find, especially since the EGR block has been tried and not proven to eliminate the problem.
Edited by: TxChristopher

Guys a couple of basic points of cooling system fuctions. When hot the cooling system is preasurized. expanding the hoses as much as possible. When it cools off if any coolant has been pushed into the overflow tank the cooling system preasure will be reduced to the point of creating a vacume at which point it will suck any coolant it pushed into the overflow tank back into the radiator. If there is suffciant suction it will flatted out the top hose. The bottom hose should have a spring in it to keep the water pump from flatting it out when running. To see a flat hose on the top of the radiator when not running and cold is perfectly normal. THAT IS THE ONLY TIME IT COULD BE FLAT! IF IT IS FLAT ANY OTHER TIME SOMETHING IS WRONG

We are in agreement with all of that. I know for a fact that the first section of my lower hose is soft and pliable, no spring in it and it would take very little for the pump to pull it down. I was very suprised to not find a spring in it.

We are looking at BOTH hoses and possible reasons they might be flattening WHILE RUNNING which is what others have seem to have posted. If we mistook what they reported then its sorta a dead issue, except the lower hose still could be getting sucked down either fully or partially causing a restriction leading to overheating. It didn't alarm me much about the upper not being a reinforced hose even from the start of this idea, but it did and still does about the lower one.

Right. I have seen my hose flat when the engine was up to temp but it was not running, I don't think that is 100% conclusive, but it is not good. Got to check while running.

exford: did you geta chance to compare the lower hose on the LB7 to the LLY? I am talking about right where it comes out of the radiator and before that line tee's into it. The LLY one is soft and no spring, it is bothering the hell out of me that a lower hose has no spring protection to keep the pump from sucking it flat.

Especially since the new pump is capable of more flow than the LB7 one......even the same hose may no longer be sufficient under the conditions the new pump presents.

Two items.

1) Aftermarket springs are available to keep the hoses open. Those
with a problem should buy one and try it out. This would be the simplest
fix ever. If no spring is available, wind one out of 1/8" ceiling
suspension wire from Home Depot.

2) My local Chevy deal says he knows of no problems, and doubts there is
one! Does anybody have a list of GM buy-backs and/or know problem
cases? The evidence here is much too strong to dismiss.

I am meeting him in an hour. I'll let you know after lunch. (Mountain time) I am still bothered with the top hose being flattened when the system is still warm. The only way that I see that hose being flat is when it has completely cooled down. This still could be a sign of something else like a bad thermostat and putting a heavy duty hose with springs will only mask it. The top hose will only have a little more pressure than the bottom hose. How much pressure do you think the radiator drops? I would figure the max would be 5psi or so, but that is only a guess based on what is acceptable pressure drops for a coil in HVAC. I would say that the top hose is still considered to be on the suction side of the pump. The major restrictions being the water jackets, egr cooler, turbo cooler and thermostats. Wish I could test this but I am not planning a trip for 2 weeks.

My dealer said only one other guy complained and he wasn't using T/H mode. I believe that TX proved that the tranny temps don't directly affect the engine temps. Might come out different with a load on.

No way anyone could convince me the alli has a significant effect on the LLY cooling system after yesterday. The alli temps flew up and STAYED UP over 230 close to 240 during my ridiculous 10 minute stall test. I wasn't being nice to it at all, there was no airflow over the truck except what the fan provided once the engine got close to 210. The engine NEVER fully covered the 210 mark during any of this, it was exposed to the allisons temp that whole time and then 30 minutes more as the allison took FOREVER to get back to 180.

Based on that test I don't see how T/H could affect anything other than the tranny temps.


Remember: the thermostat is DESIGNED to be the restriction in this system, according the GM literature. That is the ONLY reason I am willing to buy into the upper hose getting sucked flat, it exposes the entire radiator to suction from the pump, otherwise only the bottom hose is suspect and could turn out to be a problem as well (no spring).

Is there a chance of adversely affecting the system drawing from the reservoir by using a hose that won't collapse? JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

You sorta lost me with "reservoir"......

There are no negatives to having non-collapsable hoses on the inlet and outlet of the radiator other than they cost more......if this is what you were asking......

Some peopel might be wondering why it is the thermostats are designed
to provide a flow restriction. The best discussion of why, in all the
required real-life and technical detail is provided in AG Bell's two fairly
recent books "Four Stroke Performance Tuning" and "Two Stroke
Performance Tuning". The main idea is the pump creates a dynamic
pressure when it is turning. Added pressure increases cooling.

This is not simple concept, but if the static pressure is 10 PSI, the pump
might produce a dynamic pressure of 50 PSI. The thermostat as a
restriction is an important tuning tool in distribution of pump pressure,
and thus cooling, to places around the water jacket.

Of course if the hoses flatten all bets are off. Flat hoses are a hard one
to detect, but a very old idea.

TX, reservoir aka "overflow tank". Sorry about the terminology! JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

I kinda thought you meant the "overflow tank", its technically an expansion tank, either way no because it is supposed to be a closed system with a set volume, its capacity and expansion amount decided the designed volume of the tank.

In our case the tank serves as pressure controller too since we have no radiator cap.

Good question though!

guys, I ran test #2 today, completely covered the truck grill and revved it to 2500rpm to 3000 rpm for nearly 20 minutes. Could not get the truck to get to 210 degrees. Tranny never even got to operating temp, no suprise there, this further shows they are independent of each other. There was a time underneath that the lower hose was not under real pressure, I could press it together with my thumb and three fingers, but it had resistance. The only thing I got out of this was vapor was blowing into the expansion tank, which is somewhat suprising since the temp wasnt up to 210 even. Temp in the radiator is higher than the engine maybe?????? I dunno.


My trucks needle sits at about one needles width below 210 once it is warmed up and I havent figured a way to budge it.

I was very surprised to hear about overheating problems, here's why: my duramax (LLY) / Allison was built in March 2004 and I have had no problems with overheating. I pull a 10,000 lb trailer with an additional 1500 lbs in the bed of the truck in Oregons Cascade Mountain Range and Coastal Mountain Range. Believe me I am lead footed when crossing these ranges (steep and long) because I'm always in a hurry to get over them. I usually push it to 3000 rpm for 2 to 5 miles trying to keep 65 (sometimes upward of 75) MPH up the hills and yes I hear the fan clutch engage but have never seen the temp gauge hit the 210 mark (maybe up to 205 max). The transmission cooler goes only slightly higher than unloaded driving (I don't know the exact temp but I know it's no where near red). A good number of these trips have been in the hot part of this summer because I just got the truck last spring. So I would have to disagree with heating problems with the truck, of course I only have the experience of one vehicle though!

TX, The LB7 hose setup seems the same (top and bottom), but his top hose was not flat like mine is. There is either too much suction from the pump or there is a restriction.

My truck was also built in March of 2004 and I have never gone over 210 degrees

For the guys who are not having any problems, can you inspect your hoses when you are at normal operating temp and see if they are flat at all. This would tell me hose problem or other restriction.

Doug, I am sure exford and the others just grumble when they hear what their trucks SHOULD be doing! Keep the info coming though anything helps.

exford: my hose conditions are like this. The upper hose with the truck sitting cold is oval shaped in that center area. I also want to denote sitting there cold it has liquid in it. As soon as the truck is anywhere near warm it baloons up tight, fully expanded. I have never seen it flat or anywhere near flat. The bottom hose during test #2 was varying in its tightness, although it never ever was rock hard like the upper, once the truck was fully warmed and being held above 2500rpm it could be squished without much difficulty but it had enough resistance it seemed to hold its shape.

Anyone reporting a flat hose while running? And do you guys have coolant in your upper hose when cold?

As you know, I have not suffered from overheating.


Cold, my hoses are normal.


I'll check them again after lunch when I get the truck up to temp to see if they plump up and then again later in the day to see if there is any change.


L8r.

Checked the hoses last night after a 5 hour 22k lb GCWR tow in 95* weather, no flat hoses. Checked again today at normal operating temp with same results.


There sure is a lot of stuff all around the radiator. What do the 2 large metal pipes go to? It would appear difficult for much air to get past the tranny cooler, the cooler the metal pipes attach to, and last but certainly not least the radiator that dissipates heat from the engine coolant.


I'm still not convinced that somehow the tstats weren't inverted on the production line, or someone grabbed 2 boxes of the same tstats and put them in a bunch of LLY's. Either of these scenarios could cause backpressure issues, flatten hoses and cause overheating.


Since there doesn't appear to have been any major changes to the engine coolant system during the first 9 months of production it reasons that something in the production process got off track! Same radiator, same water pump, same coolant, same thermostats? Of all of these the tstats are the only component that could be installed backwards/improperly. JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

There sure is a lot of stuff all around the radiator. What do the 2 large metal pipes go to? It would appear difficult for much air to get past the tranny cooler, the cooler the metal pipes attach to, and last but certainly not least the radiator that dissipates heat from the engine coolant.


One comes from the turbo to the intercooler, the other goes from the intercooler to the intake. The tranny cooler is relativity open. Should not be a problem for air to get through that.

Jim

All


I recently traded for a '04.5 D/A built in June. I've been watching this thread with great interest since I traded my '01 6.0 in due to overheating issues pulling my 10k 5ver.


1st trip with the trailer was was early September from Phoenix through Flagstaff to the north rim of the Grand Canyon. 750 miles on truck at the start. Anyone that has traveled this route knows it is pretty much a solid uphill pull. Several long grades to pull, one of which is 17 miles long. Never really levels out for 250+ miles.


Outside temps avg. 95 to 100. I don't remember exact details but know the engine temp never went over about 215*. Tranny stayed real close to 195*. Was able to maintain speed and pass traffic instead of being passed for a change. Fan clutch engaged no more than I would expect under the conditions.


My normal operating temps here in town are around 200 on the engine and 190 on the tranny. I have noticed now that temps are dropping into the 70's at night, the tranny runs much cooler(165 to 180) in the morning and the engine remains near 200.


I checked the hoses cold and after running around town today. No flat or deformed hoses.





Edited by: sb62

JJ: the small cooler in front you know is the alli air cooler. The big black one behind it is the A/C condenser. The big silver one behind that that is the intercooler. Behind the intercooler is the radiator. You are the nut behind the wheel ;)


See my test #2 above. I agree that it doesn't seem like much air could get thru there, but we have seen that it cools just fine when its all working properly. I never owned an LB7 truck, but after my last two tests I know what they mean when they say that the temps on their trucks didn't move, cause mine doesnt either. I blocked mine off from by far the majority of its air and I still couldn't get it hot.

Edited by: TxChristopher

Checked the hoses after getting back with engine warmed up and I see no noticable change in the hoses. Will look again this afternoon after it cools off. Shouldn't take that long today!

sb62, sounds like your LLY is performing as designed. http://www.dieselplace.com/forum/smileys/smiley4.gif Not all LLY's are experiencing the hot temps. We're trying to help the guys out that are having this problem.


TX, did you see my post several pages back describing the thermostat setup on the LLY's? If I understood it correctly the tstats are set to open at different operating temps which somehow enhances cooling efficiencyhttp://www.dieselplace.com/forum/smileys/smiley5.gif, have to admit I don't totally understand the theory.


If the tstats were improperly installed like I suggested above wouldn't it have the effect of creating either too much pressure or backpressure which could adversely affect cooling efficiency. If the thermostats aren't allowing the coolant to recirculate fast enough through the cooling system, OR it is staying in the engine too long, it could cause overheating.


I would pull my tstats but since I'm not overheating it wouldn't be the best results. Any LLY overheaters out there willing to change them out to see? If you do make sure you get them in the right spot! JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

My truck was built in may 2004 and I have never gone over 210 deg Towing 12k lb. At normal operating temp the hoses are not flat.

















________________


2004.5 Chevy LLY

New to the forum. Lots of great info for a first time diesel owner. I checked my hoses both cold and hot, they were not compressed. I have towed my 5k boat which isnt really much of a chore for the DMAX. Temp hand never moved from normal 200 degrees. GA. does not have the type hills some are pulling. Only one issue pinging/rattling during light to moderate accel. Reflashed PCM with latest update tech said all LLY dmax's he has worked on have this issue?? but didnt help other than that;


http://www.dieselplace.com/forum/smileys/hihi.gifLOVIN MY DMAXhttp://www.dieselplace.com/forum/smileys/smiley32.gif

Further info on hoses: My upper hose is the same dead cold in the morning as it is right after the truck has been run for an hour. It is full of coolant anytime the truck is not running, and for comparisons sake it also makes a "clicking" noise when you squeeze and release the hose, the sound seems to be coming from the thermostat housing. It does this whether hot or cold.





Just trying to give the overheating guys some points of reference http://www.dieselplace.com/forum/smileys/smiley1.gif





JJ: I did notice your posting a few times on the thermostats, I havent had a chance to focus on the thermostat issue as of yet. I generally try to run each possibility to its end before swinging the spotlight to the next. I am not even sure that they are possible to swap out, the top one is a two stage from what I understand.......

Mine makes that clicking noise too when you squish the top hose, Doesn't look flattened either cold or hot running or not.


When running the highway most I get up to is 210 at 70 mph outside temp was 83F, When I back off to 60 temp drops. Haven't towed anything yet.


no egr, no cat





R

I have the flat hose happening on 2 trucks, one built 3-04 and one built 5-04. I had the reflash done today and decided not to try a spring in the hoses untill I get a chance to evaluate the reflash. I have however decided to try a usb camera for my laptop to watch the hoses while I drive. It will take me a couple of days to rig this up. My top hose is the only one I have noticed flat and it stays flat from cold to driving sometime, just idling never seemed to open it.http://www.dieselplace.com/forum/uploads/RickDLance/2004-09-29_191123_DCP_1863_Small.JPG Edited by: RickDLance

RickDLance: was that pic taken while the engine was running? If so you have a major flow restriction, perhaps something stuck in the thermostat housing or the thermostat itself stuck. If that pic was taken with your truck running then I am sure you have overheat problems, in fact I am impressed your LLY is able to run at all it speaks well for its cooling system if it can operate at all crippled like that.

I feel like we are making good progress here, this problem is going to get solved. Good idea on the camera, but if it were me no way could I resist pulling that thermostat housing off and inspecting it for some foreign object, and taking the thermostat inside and dropping it into a pot of boiling water while I was at it to verify it opens.

My hoses have coolant in them at all times, cold, warm, running temp.

If your upper hose is flattened like that while your truck is running then you have near blockage from the thermostat itself or blockage in the intake manifold water passages allowing the water pump to cause suction across the entire radiator. Now I am starting to believe the oddball trucks that overheat need disassembly of the intake to see what the problem is, such as what dipsh*t assembly line person forgot to remove production line plugs, totally non functional thermostats etc.........you have blockage period and it isn't going to go away without opening that baby up.

If there is no obvious blockage at the thermostat housing then you must force the stealer to remove your intake for examination. It has to be done.
Edited by: TxChristopher

That picture could be of my truck hot or cold when not running. I will look at it running when I get a chance.

Maybe we should replace our hoses with the following Goodyear hose? Does anyone know of a better one?

http://www.goodyearbeltsandhose.com/cars/wirerad.html

http://www.dieselplace.com/forum/uploads/cadent45/2004-09-29_221004_Radiator_Hose.gif

Coming into this late but after doing some reading and some searching on the internet for collapsed upper hoses thought I would offer up another view point. I appologize if any of this has been brought up already but with so many posts, I didn't see it.


I found what look to be similar circumstances on 2 different sites with 2 different remedies. Not GM related but the theory should be the same.


#1 Aussy site: Late model Landcruiser w/Turbo Diesel engine. Cooling issue under moderate to heavy use with collapsed upper hose. Fix: Owner installed suport spring in hose. Toyota did not acknowledge as a legit problem. If it were my truck with the problem I would not buy into this fix. I think it would be masking the real problem. Could be a weak hose but rubber molding technology has advanced significantly through the years and as a result become very consistant.


The 2nd site dealt with Lancer cars. Collapsed upper radiator hose with marginal cooling capacity. The OEM published a TSB calling for the replacement of the radiator pressure cap. It appears as though a number of caps of questionable quality and pressure ratings randomly made it to the assembly line. The faulty caps did not allow the cooling system to relax after cooling down from normal operating pressures, creating a vacuum on the system, thus the collapsed upper hose.


If I were having problems with mine, I would buy the cap out of my own pocket(or at least make them do a pressure test) before letting the dealer tear the top end off. As I stated earlier, I think the support spring in the hose is masking the real problem.


Just my .02


Steve

Guys, I can be a pain in the azz for sure, and I hate to cover old ground twice, but if you havent made sure you have the proper coolant mixture and that your system holds 15psi pressure then shame on you, you deserve to have an overheating truck. The only reason I ranted about coolant mixtures and pressure caps in the first place was in the hopes that someone that hasn't done that would have gotten motivated and eliminated that possibility. I would think that the stealer would also have eliminated thermostats and even pumps on some trucks, those are common sense shot in the dark things that joe blow mechanic would try.


sb62: if we are talking a running engine that has a collapsed hose then your #2 situation does not apply. RickDLance said "it stays flat from cold to driving sometime, just idling never seemed to open it". The only way I will accept my theory of the water pump being able to pull down the top hose is at HIGH rpm, after it has gained and gained on the system through high head pressure and high suction because GM upped the pump output and may have left the rest (including the designed thermostat restriction) the same. In such a case the spring hose would solve the problem.


However, RickDLance said idling and nobody is going to convince me the pump is that powerful that it can gain suction across the radiator versus pump output at idle. After long periods of high rpm, maybe. But not at idle.


If that pic was idling then you have a physical restriction that is allowing the pump this ability. There just isnt enough flow at idle otherwise. It may be a stuck thermostat or a foreign object in it, the first place to check would be the thermostat housing. But lets be clear, if you dont find anything in there and the thermostat is operating correctly, then that intake HAS to come off for inspection of the intake/head water passages. I would also say the heads need to come off as well but there are so many passageways between the heads and the block that it would be hard to believe that blocking one, two, or even three or more of them would result in the kind of blockage needed to give the pump ability to pull down the upper hose at idle. I know nobody wants to hear this but I dont see any way around it.


If I am missing something please someone step in, I am not perfect and make mistakes for sure........


*On edit: it would seem obvious but I dont wanna leave stones unturned, have you made sure that hose is not twisted by loosening the clamps and freeing the hose from the piping? This is dependent on it looking like that pic with engine off not running, pressure running would force even a twisted hose to baloon out beyond what I am seeing in that pic.





Edited by: TxChristopher

The picture I posted was cold. I tried to let it warm up and the hose stayed collapsed. I drove it around the block and it was ok then. My dealer has replaced both thermostats on 1 of the trucks. I like the cap idea, but I am still going to try the camera. When my truck heats up it does it so fast the flatened hose idea seams logical.

Rick, you say after you drove around you had a round hose?

JJ: haven't had a chance to look into the physical aspects of whether it is possible to swap the two thermostats, but assuming they are of the same shape and size the worst case would be that they would both still be open by 212* and if the rest of the cooling system were normal you still wouldn't overheat. The truck running warmer than the normal trucks just cruising around would seem to be the penalty.

While we are talking temps, there should be flow through the top hose when temps reach 180*, at this point the hose in RickDLance's truck should expand out.

Chris/Rick/JJ


Not meaning to argue so please don't interpret my comments that way.


I don't see how the collapsed hose on a cold truck can be anything but a cap issue. When cold it has nothing to do with a flow restriction. The cap is simply not relieving the pressure after cool down and creating a vacuum on the hose.


Has anyone looked into flow testing the cooling system? I realize it may end up with the same end result, but I am very apprehensive about letting anyone tear into a new engine. There are still too many checks that have not been performed.


My best advise would be to find a independent shop that specializes in cooling systems. Talk to them, ask them to flow test the system. That will point out any flow restriction. Take the diagnosis/bill to the dealer/GM.

Edited by: TxChristopher

sb62: not taking your comments as arguement at all. The whole point of a forum like this is to share ideas, so keep it coming!

I agree with you, a collapsed hose on a cold engine is no big deal. His is probably more pronounced since he overheats and loses coolant routinely, so a decent vacuum is created at cooldown. He could relieve that by opening the expansion tank to atmosphere and perhaps adding more coolant.

We are taking issue with the upper radiator hose STAYING flat while the engine is running, RickDLance even went so far to say he drove around some. Engine is warm and hose is still flat.

I totally agree also on the testing, that was the first thing I ranted about at the start of this thread. I think some have gone thru the replace and see method of testing (stealership) and the problem persists. Seems the stealer would replace the easy components (thermostat, cap, water pump) in an attempt to solve the problem. Has the stealer done these things guys??????

Maybe it will help if the guys that are overheating will tell everything that has already been done to solve the problem so we can avoid running over the same ground again and again.

So lets hear it guys!

As far as I know the pressure cap is a one way device, it doesn't serve to let in outside atmopheric pressure upon cooldown. All it does is hold a certain psi and it gives up when that is exceeded. Any vacuum pulled on it by the cooling system would only serve to help seat the caps plunger harder.

I don't get the the thing about the cap not "letting the system relax"....to me that has no foundation as that is not the function of the cap.

a hose colasping on a cold engine IS A PROBLEM. The reason it is collasping is that the system is not full of coolant as it should be. When a sytem cools down, it is designed so that if there is not enough coolant in the system, it will create a vacuum. Once the vacuum is high enough, the radiator cap is supposed to allow the vacuum to overcome the spring pressure and allow the rubber seal to come off its seat (inside the radiator neck). Once this happens, the vacuum then pulls coolant out of the overflow tank to replenish the missing coolant in the system. This does not happen all at once on just one heat up/cool down cycle. It takes many cycles to replenish the coolant in the sealed portion of the system.





If your upper hose and or lower hose is collasped when you have a completely cold motor (that has not been started for the day), then you have a RADIATOR CAP THAT HAS GONE BAD. The cap should never allow enough vacuum to be created that would keep the hoses collasped.


If your LOWER hose is going flat while the motor is running at full operating temp (or overheating), then you have a restriction in either the thremostats, upper radiator hose, or the radiator itself. The Lower hose is on the SUCTION/SUPPLY side of the water pump. The Upper hose is on the PRESSURE/RETURN side of the water pump. The only way a lower hose can be sucked flat is if the suction side of the water pump is being starved for fluid. It then creates a vaccum on that hose and once the vacuum is high enough, it collaspses the hose and stops coolant flow.


I've worked on Car's, trucks, tractors, and boats for 30 years...... 99% of any vehicle that has a support spring in a radiator hose will be on the hose between the suction/supply side of the water pump and the radiator. On our trucks, that hose is the lower hose.......


Older vehichles usually always had the support spring, but newer mfg techniques on modern rubber hoses had eliminated the need for the support spring on many models.


RickDLance's picture was taken with the motor off. Look closely at the printing on the fan belt, and the blades of the cooling fan itself. There is no movement indicated on either part. It would take a very expensive high speed camera to take a picture of a running engine and make it appear to be absolutly still. Edited by: Searay90

Help explain to us why an upper hose would stay flat after an engine had warmed up.

Also run that part by me again about the cap allowing stuff back in, we have an expansion tank that is open directly to the radiator (hose running from top of radiator to bottom of expansion tank). Are you telling me the cap is a two way pressure control device? Cause that's a tuffy for me to buy. Must have a spring loaded check ball, never looked at it close enough.
Edited by: TxChristopher

As far as I know the pressure cap is a one way device, it doesn't serve to let in outside atmopheric pressure upon cooldown. All it does is hold a certain psi and it gives up when that is exceeded. Any vacuum pulled on it by the cooling system would only serve to help seat the caps plunger harder.

I don't get the the thing about the cap not "letting the system relax"....to me that has no foundation as that is not the function of the cap.



Actually Chris it does have a vent valve built in. The following should explain what I'm talking about.





http://www.dippy.org/svcman/image/working/0702.jpg


Radiators are equipped with a 14-18 psi (97-124 kPa) pressure cap as standard equipment on all models


The system can operate at higher than atmospheric pressure which raises the coolant boiling point allowing increased radiator cooling capacity. The cap contains a pressure relief spring loaded valve that opens when the pressure exceeds 14-18 psi (89-124 kPa) (Fig. 2 (http://www.dippy.org/svcman/image/working/0702.jpg)). There is also a vent valve in the center of the cap that allows a small flow through the cap when below boiling temperature but is closed by an increase in flow as the boiling point is reached.


This valve also opens when coolant is cooling and contracting allowing coolant to return to radiator from coolant reserve system tank by vacuum through connecting hose. If valve is stuck shut the radiator hose will be observed collapsed on cool down. Clean the vent valve (Fig. 2 (http://www.dippy.org/svcman/image/working/0702.jpg)) to ensure proper sealing when boil point is reached.


There is also a gasket in the cap to seal to the top of the filler neck so that vacuum can be maintained for drawing coolant back into the radiator from the coolant reserve tank.

Will have to look at the expansion tank cap when I get home. I have been wrong before (many times!) although our cap is not a radiator cap as pictured, the radiator has a direct line to the bottom of the tank, coolant does not need to flow thru the cap to get back to the engine.

The radiator cap is a "two way" valve (your term). It allows coolant from the cooling system to "overflow" into the holding tank when the motor overheats, or is running sufficiently over full that it needs to allow some of the coolant to leave the sytem. This happens when the pressure in the cooling system over comes the seat pressure of the radiator cap (14 to 18 psi as mentioned above). When this happens, coolant leaves the cooling system thru the overflow hose until enough pressure (volume of coolant) has dropped to allow the radiator cap to re-seat itself (pressure drops to below 14 to 18 psi).


When you stop the engine and it cools for a long enough period (usually overnight)....... if there is enough vacuum (caused by not enough coolant in the cooling system itself), it will unseat "THE OTHER" valve in the radiator cap and allow the system to suck coolant back out of the overflow tank and replenish the cooling system. But as I said earlier, if you had a significant amount of coolant blow into the tank (or boil over = all over the side of your truck), a single cool down cycle will not fill your cooling system "back up" from the over flow tank. If you have a "boil over", do not rely on the coolant tank to refill your cooling system. You MUST let it cool down, and fill the radiator by removing the radiator cap and adding coolant directly to the radiator. Failure to do it this way will result in continued overheating because the cooling system will not be full of coolant after one "cool down" cycle.

Here is a picture from another post on this site. Wish I had my truck here at work so I could go out and see exactly how our system is connected visa via the hose coming out of the top of the tank on this picture. (Wifes Yukon XL in the body shop for hail damage, so I driving my honda VTX1800R today http://www.dieselplace.com/forum/smileys/smiley1.gif) That hose is clearly NOT on the pressure side of the system. I suspect that if you follow it, it will either connect to the actual radiator cap, or another tank which is the actual overflow tank. If the tank in this picture has an inlet and outlet coming off the bottom of it, then this tank is a "Surge tank" and not an "overflow tank". The terms reference tanks which serve two different functions. If (and I mean if) our radiator caps do not act in the same manner upon cool down as the one shown in the post above, then you would only be able to add coolant to the system when the motor was absolutly cold. If you topped it off hot, then it would always collaspe the hoses when it cooled down because there would be no way to compensate for the reduction in coolant volume when the liquid cooled back down. I'll try to remember to get out the digital camera when I get home and post some pictures.

AFE stage 2 intake
http://img.photobucket.com/albums/v216/2002bolt/DSC00267.jpg

That's what I was trying to get across, our tank is an expansion tank, or surge tank if you want to call it that. There is no "radiator cap", only the cap on the expansion tank. The hose out of the top leads to atmosphere, its an overflow, and there is a hose that leads from the top corner of the cool side of the radiator to the bottom of the expansion tank. That's the whole system.

As far as I knew our cap was a 15psi pressure controller for the system. When I get home I will check to make sure if it has a spring loaded check ball system to allow for system vacuum to pull in fresh new atmosheric air.

Went out and looked at mine to verify.


On the cap, the tank is identified as a surge tank.


The tube shown on the tank above is open ended between the air cleaner and surge tank. Provides the vent and also provides a means to expell access fluid in a severe overheat condition.


There is 1 hose coming from the top of the radiator to the bottom of the tank. As coolant heats up and builds pressure, the coolant transfers to/from the surge tank via this hose. The fluid level should never drop below this connection on the surge tank.


There is no cap on the radiator itself. The cap on the surge tank maintains system pressure. The only reasonable way to fill is through the surge tank.


Although the physical appearance of the cap may be different, it functions the same way. You must have a way to vent the surge tank. Otherwise coolant would not flow back to the radiator until vacuum was sufficient to collapse the surge tank.

Man I'm slow. You posted while I was typing Chris.

Since you are home and I am driving a different vehicle down the road, pull off the expansion/surge tank cap and see if it has a spring loaded check ball/relief valve. My understanding was that the tank would accept the expansion of the coolant, and since it was under the exact same pressure as the rest of the system that upon cooling the pressure would drop system wide and allow the coolant to gravitate back into the radiator (seek level). When the truck is getting hot the first thing that happens is vapor blows into the expansion tank past the resting coolant in it.

So the tank has pressure, not sure it would need to vent to atmosphere to allow coolant to return to the radiator. I thought our system was a closed system. Then again, like I said, I have been wrong before :)

Hmmm my posts are landing twice on here ...... I need a post overflow cap!!! LOL!!! Surely we can figure this thing out guys, its not an arguement it is a learning experience and a fact finding mission so please don't take anything I say wrongly. Thanks!

-end transmission-

.Edited by: TxChristopher

Christopher, what part of town do you live in?


Maybe we can get our heads together on this problem. My 2500HD has'nt had any overheating problems towing my 14K fifth wheel over the 610 bridge over the ship channel on many occasions in our Houston heat, so I've just been lurking with interest on this forum and the other forum that dealt mostly with blaming the EGR for the overheating. I think that now, though, a real solution may be in the works with this cooling system business, as indicated by the collapsed hoses.


2004 2500HD, Metallic Gray, CC, SB, D/A

Hey, we've all been wrong before. LOL Just ask my wife and kids! We might all be wrong now but that isn't the point. When I learn something new (which I have) it's all good! We just need to figure out how this all works.


I had to drop some family off at the airport so it took a while before I could pull the cap. Took a couple of pics of the cap.


http://www.dieselplace.com/forum/uploads/sb62/2004-09-30_144828_Cap1.jpg





http://www.dieselplace.com/forum/uploads/sb62/2004-09-30_145000_Cap2.jpg


The metal disc sounds like it floats. Rattles when you shake the cap.


The way I understand the system you are partially correct. And this only holds true if the hose is collapsed on a cold engine. It may very well take a few miles of warming up to expand everything back to normal.


As the engine heats up, coolant expands, pressure builds and forces coolant to the surge tank. The pressure is sufficient enough to overcome the resistant pressure in the surge tank and access coolant flows.


As the engine cools down, the coolant contracts, pressure drops into the negative and this vacuum "sucks" coolant back to the radiator. Until the vacuum is equalized between the two. At that point the vacuum in the surge tank works as sort of a "brick wall". Flow is stalled. Without a vent on the cap, there will be no more flow and the weakest link will succumb. This is what I believe is collapsing the hose.

I live in Webster off W. Bay Area Blvd @ Pilgrims Point. Back behind Baybrook mall.

I aint buying into the EGR causing the overheating, I have read that other thread on here......and I monitor it still for any ideas...."engine temps" I believe it is called.

There has got to be some sort of valve in that over flow hose, otherwise that pressure cap is pointless. Unless the overflow hose is lined up with the cap just like a radiator cap. Something should be able to release the vacuum. Temp goes up pressure goes up. Cap allows pressure to build to 15. Over 15 the cap should allow overflow to blow vapor/coolant. As pressure drops back down to negative, it should let air back in through the cap or the overflow line. I have removed that cap before and never noticed any kind of pressure or vacuum when it is cold. If a problem here was making my hose flat, opening that cap would have let air in and expanded my hoses. If I have coolant in the surge tank, wouldn't that relieve and expand the hoses? I am going to take a look at this system tonight.

There has got to be some sort of valve in that over flow hose, otherwise that pressure cap is pointless. Unless the overflow hose is lined up with the cap just like a radiator cap. Something should be able to release the vacuum. Temp goes up pressure goes up. Cap allows pressure to build to 15. Over 15 the cap should allow overflow to blow vapor/coolant. As pressure drops back down to negative, it should let air back in through the cap or the overflow line. I have removed that cap before and never noticed any kind of pressure or vacuum when it is cold. If a problem here was making my hose flat, opening that cap would have let air in and expanded my hoses. If I have coolant in the surge tank, wouldn't that relieve and expand the hoses? I am going to take a look at this system tonight.





There is no valve in the hose that I could find. It is supposed to work just as you stated. If your surge tank is not under vacuum cold, and your upper hose is flattened, that pretty much blows the cap theory out of the water for you.

I just checked my truck and the upper hose is collapsed when cold.

Ok guys, I ran test #3 today after rattling all over the function of the overflow/surge/expansion tank and the cap that is on it with a couple of guys on here. We had a more than productive discussion on this. Now on to the results:


These are pics of my hoses, I was able to duplicate the flat hose along roughly 80% of the length of the hose:


http://www.dieselplace.com/forum/uploads/TxChristopher/2004-09-30_181652_hose-2.jpg


http://www.dieselplace.com/forum/uploads/TxChristopher/2004-09-30_181449_hose-1.jpg





I duplicated this by having the wife take the cap off of the expansion tank, then I physically twisted and squeezed every bit of coolant out of the hose I could then had her screw the cap back on. It is hard to see in the pic because they were flat parallel to the ground which made it difficult to get a pic because there is no room to get a camera in there from the side, but trust me the hose is flat all but the final maybe 2" or 3" of each end.


Now for what I discovered. Dexcool tastes crappy! Also I found that the cap does indeed have a relief flap in it. I proved this first by sucking directly on the part of the cap that faces the inside of the tank and is exposed to the tanks pressure (which is where I got to sample Dexcool http://www.dieselplace.com/forum/smileys/smiley4.gif) which produces a rubbery flapping sound and even a cute little horn sound sometimes, but flow nonetheless. The second way I verified the relief valve was by blowing into the overflow hose back into the expansion tank and watching the hose expand back out. So yes there is a relief valve that will allow some air back into the system.


Now, if you are asking why the hoses are staying flat if there is a relief valve present, the answer is that the collapsed hose does not possess enough suction power from the spring of its own walls to overcome the relief flap in the cap. If you remove the cap, the hose instantly moves back to its correct shape. Otherwise it will stay that way probably forever as long as the engine is not running.


The value of all of this was only to provide info on a flat hose in a cold non-running engine.


I have never thought a collapsed hose when cold is anything other than an indication of a system that is a little low on coolant, and I said that earlier specifically about RickDLance's truck when I posted "I agree with you, a collapsed hose on a cold engine is no big deal. His is probably more pronounced since he overheats and loses coolant routinely, so a decent vacuum is created at cooldown. He could relieve that by opening the expansion tank to atmosphere and perhaps adding more coolant"


Please dont anyone take any of this wrong, I am glad that we looked at the overflow/surge/expansion tank and its cap do for a living. I just dont want to get sidetracked on something that isnt the problem, I want to move on looking at symptoms or issues or ideas that cause the overheating, not evidence left behind after the truck has overheated.


Now if anyone can report a collapsed hose while the engine is running and at least 180 degrees then we have something to go after. A collapsed hose while running is what we have been talking about and what we are trying to verify can exist under a load. We also need to know from the guys with the overheating trouble what has been checked and or replaced trying to defeat this problem.


If someone has a truck that is an overheating machine, and the system has passed pressure tests, has the correct 50/50 mixture of coolant in it, has had thermostats and water pumps replaced, and is STILL overheating then you have no choice to move on to physical obstructions in either the radiator or intake manifold. The radiator would be the easiest to clog so maybe get the stealer to replace it and have at it again. If those prove to be free and clear of obstruction

On a more positive note (at least for me http://www.dieselplace.com/forum/smileys/smiley32.gif) my gtech pro rr should be here maybe monday or tuesday. The local stealers threw up a wall on the H2 wheels/tires, around here seems they return them for core money or they want WAY too much for them. Either way I got tired of trying to chase those down so today I took the truck to dicount tire and had 285/75's put on my truck. I hated how the truck looked with the tiny tires on it, so i feel good about making the change there, but I am somewhat regretting not waiting for the gtech so I could establish 100% stock baselines. Now I am considering renting an HD after I get the gtech so I can do a temporary tire swap for baseline testing LOL http://www.dieselplace.com/forum/smileys/hihi.gif !!!!!!!!

Once I can get some time to take a drive, I will post the hose condition. I have seen it flat when it was hot, but it was not running. I think that it should not be flat when warm unless something is wrong. It doesn't take much to get up to temp so I will drive to work tomorrow.

TxChristopher
Now for what I discovered. Dexcool tastes crappy! Also I found that the cap does indeed have a relief flap in it. I proved this first by sucking directly on the part of the cap that faces the inside of the tank and is exposed to the tanks pressure (which is where I got to sample Dexcool http://www.dieselplace.com/forum/smileys/smiley4.gif) which produces a rubbery flapping sound and even a cute little horn sound sometimes, but flow nonetheless. The second way I verified the relief valve was by blowing into the overflow hose back into the expansion tank and watching the hose expand back out. So yes there is a relief valve that will allow some air back into the system.


I just finished watching the debates and went out to the truck before reading your posts. I found out a couple of things: 1) we don't have an "overflow" tank to capture coolant when the engine overheats. The hose just blows it all over the fender. 2) Like you dexcool does not taste good, but I like you did confirm that the surge tank cap has a relief valve in it that allows the system to equalize with atmospheric pressure when the motor cools down. When I unscrewed the cap, I noticed a very slight sound of vaccuum being released. I did the old vaccuum test with my mouth and it did not take much at all to get the vaccuum relief valve to break loose. Maybe your vaccuum relief valve is taking too much vaccuum to release (and then equalize), causing your hoses to collapse.


A cheap test would be to go buy another cap, then fill the system up to specs while the engine is stone cold. Put on the new cap and drive it for 20 miles or so and get it good and warmed up. Then park it and check the hoses the next morning and see if they are collapsing or not. If not, then you found the culprit that is causing the collasped hoses.





FYI the clicking you guys are hearing when you squeeze the upper radiator hose is the small relief valve that most every modern OEM thermostat has. There is an 1/8 inch hole drilled into the housing of the thermostat that allows a small amount of coolant to pass thru it when the thermostat is in the closed position. This allows the thermostat to function better as it has coolant flowing thru it vs stagnet water being around it. In other words it heats up to the same tempature as the water quicker. It also allows small pockets of entrained air to pass out of the thermostat housing and up into the surge tank when the motor is shut off. Most thermostats that have this bypass hole, also have a small piece of metal with a botton head on the top side. The button head is on the top of the thermostat flange, then a very small shaft (either round or stamped flat metal) goes down thru the hole (smaller than the diameter of the hole), and is then bent at the end to keep the thing in place. it has about 1/8 of play built in so when the water pump is turning, the pressure will lift the "button head" off the thermostat flange and allow a small amout of coolant to pass thru it. When you shut off the motor , the button head seats back on the thermostat flange. When you squeeze the upper radiator hose, you are causing coolant to move thru the thermostat housing and are causing the button head of the bypass valve to lift up, and the bottom retainer on the valve to click against the bottom of the thermostat flange. Then just a quickly the coolant stops moving and the bypass valve falls back in place with the top of the button head seating against the top of the thermostat flange. That gives you the second click. Wish I had a picture so I wouldn't have to type so much describing these things. But heck, I used to write maintenance procedures for government missle systems so this is nothing.


Found an example of a thermostat wit

OK, I found out something interesting today, that you all might find interesting. I don't know if this has been brought up yet, but to be honest I didn't want to read through 12 pages, so here goes. You all know by now there are 2 thermostats. The one in the front opens first and the one in the rear opens next. I don't know the exact opening temperatures, but I'll try to find them. So here's what I'm getting at, the 2 t-stats sit on top of that cross-over pipe that connects the 2 heads and theres a tube on the bottom that goes back down to the water pump. If you look at the operation of it, theres a "flapper" on the bottom of the second (rear) t-stat. When the rear t-stat is fully open, the flapper valve, which is on the bottom of the t-stat goes down and closes off the bypass, so that all coolant is directed to the radiator. Its a long shot, but if the crossover/bypass area isn't cast right, it could cause alot of coolant to still get bypassed when the engine is hot. Just a thought.

<?:namespace prefix = v ns = "urn:schemas-microsoft-com:vml" />Basically, the rear thermostat has a round, flat piece attached to the bottom of it. As it opens fully, the t-stat begins to move downward opening the t-stat, and at the same time, since the flat piece is attached, it goes down and closes off the bypass.</v:shape>

Searay90, I call that a rattle valve. But you know what I mean. You can see the bottom flat piece that moves down as the t-stat opens. Sorry for so many posts guys, I posted before I saw his pic.

I dont suffer from either the overheating or the collapsed hoses (thank the lord almighty!) but in my test #3 above I did show that the collapsed hose alone doesnt have the ability to overcome the relief valve. I also discovered today by swinging by the parts house that nearly every GM car or truck today uses the exact same cap as ours to control the system pressure. Cheaper that way to make one part and put it on everything I guess.


Thank you for the info in the clicking sound, beats me having to disassemble it to see what it was. By all means feel free to toss in ANYTHING you think will help nail down this overheating problem!!!!!


socaldieseltech: maybe i can save you the time on those temps:


After the coolant temperature reaches 82°C (180°F) the front thermostat primary valve opening temperature, the front thermostat primary valve will start to open. The coolant is then allowed to circulate through the thermostat to the radiator where the engine heat is dissipated to the atmosphere. As the engine coolant reaches 85°C (185°F) and more coolant demand is required the front thermostat secondary valve begins to close the bypass port and the rear thermostat begins to open coolant flow to the water outlet. The thermostats will continue to control the coolant flow by opening and closing. The front thermostat will be fully open when the coolant temperature reaches 95°C (203°F) the rear thermostat will be fully open when the coolant temperature reaches 100°C (212°F).





Another good theory, moves us into the manifold where it seems we were already heading anyway. Anyone out there have any ideas.....no matter how wild.....bring them out.....

Yeah I have seen that on thermostats over the years, usually on the stock ones as they go into the trash when being replaced by a robert shaw high flow unit!


Guess we can put that to rest, it was just a detail sound I noted when playing with the hose and wanted to see if the overheat guys had the same thing.

I would look at that coolant crossover pipe.

Searay: you have any ideas on exford reporting his upper hose flat when hot????


socal: if posting 6,000 times will reveal a fix then get busy dude! http://www.dieselplace.com/forum/smileys/hihi.gif

Hose is normal when hot. Crap, hoped we had something. Looks like flat hose is just sign that it does get hot. I will keep an eye on it.

Interesting? I was checking out some posts on the LB7 site, several guys with 04 LB7's reported the exact same high temperature issues as the LLY's, i.e. 230* engine temps and tranny temps up around 210* on steep grades towing heavy! Earlier versions of the LB7 didn't experience this. HHHHHMMMMMMMMMM? http://www.dieselplace.com/forum/smileys/smiley24.gif


So what changes were made to the LB7 from 03 to 04 that were then carried over to the LLY's? JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

Maybe they had a bad run on those crossover pipes I was talking about. I think they are the same on the LLY and LB7 not 100% sure though. If so, possible that some late LB7's got it and early LLY's. Is anyone overheating on trucks with the later build dates? I spoke with a guy at TAC on friday afternoon about this and brought up with him what I saying about the coolant crossover pipe and the t-stats operation. He was VERY interested in what I had to say. I was also noticing that in none of the service material does it state how the t-stats function in the way I described, using the flapper valve to shut of the bypass pipe back to the water pump. I just happened to stumble on it while glancing over a DMAX training booklet. I'll quote some stuff from the book. I also want to apologize for my misquote, the bypass (secondary) t-stat is the forward one. Here's a few quotes--


"The secondary thermostat or bypass control thermostat is located within the front of the thermostat housing. This single stage t-stat controls coolant flow and the operation of the bypas flapper valve. When this t-stat is closed, the bypass flapper valve is open to allow coolant flow within the engine only for faster engine warm up. The bypass thermostat befing to open at 185F. As is begins to open, it also begins to close the flapper valve. When this t-stat is fully open at 212F, the bypass flapper will be fully closed, allowing maximum coolant flow to the water outlet and on to the radiator." -- "With both t-stats fully open, coolant flow is 300L per minute, or almost 80 gallons per minute." ---end of quotes-- I was also noticing in this book that this book has 5 pages dedicated to cooling system component operation, of which 2 full pages are about t-stats and their operation. What do I think? I think that 80 GPM would be enough to cool even a bad engine that truly had an overheat problem. Unless it wasn't really flowing 80 GPM to the radiator because of a coolant flow problem. Just throwin this out there.

Usual disclaimer: I ain't "meck-a-nickel-ally" inclined so be gentle. JJ's hypothesis after reading the most recent postings! http://www.dieselplace.com/forum/smileys/hihi.gif


LLY's run 205-210* normal operating temp, allison 150-190 depending upon driving conditions. It is only when pulling heavy, say over 10k lbs, up steep grades with hot outside temps that some LLY's are overheating. So what is happening under the hood? Hang on boys!http://www.dieselplace.com/forum/smileys/hihi.gif


We lay into the accelerator to keep our speed up, gravity starts working against us so we push a little more on the accelerator introducing more fuel for combustion for more power. More fuel means heat, lots of it! Allison heats up as well trying to hold load, putting more heat to the radiator. RPM's are high, temps begin to climb, tstats fully open for max coolant recirculation. The water pump is now cranking 80gpm of hot coolant, radiator hoses get extremely hot making them even more pliable. Is it possible the hoses get sucked down by the water pump, then once the climb is finished and the conditions subside, RPM's return to normal range, etc., the water pump decreases its draw on the hoses they reopen and coolant circulates normally. This may explain why the temps drop so dramatically after the hard climbs.


The high temps only happen while the truck is running at very high RPM's under significant loads so we're unable to see it while driving. If you finish a climb running hot, stop the truck and pop the hood too quickly you will burp the truck since it needs the higher rpm's to cool as well. Also, at idle the water pump isn't putting enough suction on the system to compress the hoses.


Has anyone replaced their radiator hoses with the ones with springs and towed heavy in hot temps to test this theory? JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

When I did test #2 I did find that the lower hose was marginal. It is the one that should have the spring in it. The higher flow pump may be collapsing it, mine was easy to press closed with just a thumb and three fingers when up to temp. Wifey couldnt hold the truck at a steady rpm so the water pump never got to work and work and work to have a fair shot at collapsing it, whereas if you were towing it would.


I wish RickDLance or someone would at least try a spring in the lower hose so we could eliminate that.


What was the flow of the old water pump? 80 gpm sounds like a lot of flow to me for the new one, I wonder how much of an increase it was.


The theory on the bypass is still working, its possible but would take a good bit of water going to the bypass to make the kind of difference we are talking about. The way these guys are describing the overheating it happens QUICKLY.

Several of the guys with 04 LB7's reported the same problems towing heavy, up inclines in hot weather. Exact same temps for engine and tranny. Previous years LB7's ran much cooler, the only ones that ran higher temps were those with aftermarket programmers or tunes.


Whatcha wanna bet GM used the same water pumps in the 04 LB7's? JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

I am sure they did.....the literature on the pumps is dated january 04.....how far into the year did they go with the LB7 before the LLY was started up? I know my truck is 04/04, but people always seem to say 2004.5 LLY.


To me the pump is the only big change in the system. Catching the hose collapsed will be impossible though, so someone just has to try the mod and see.

I am going to try and mount a USB camera to monitor the bottom hose. I would rather see it happen, than just assume it is.

That's a good idea Rick, your idea is really the only way to actually prove it. There is a LOT of real estate on that lower hose, hope you can get an advantageous view to be able to see the whole thing.

I was only recommending the spring inside since it would be really easy and inexpensive to add to the existing hose and would eliminating the possibility of collapse, so after that if the problem was still there collapse could be eliminated the source of overheating.

Just trying to scratch potential problems off the list......

My understanding is the LB7's were installed until the December 2003 timeframe, then the LLY's started coming out in January 2004 or thereabouts. Interesting part is the LB7 pulls like a frickin mule without overheating, their main problem being the injectors. Several guys that bought 2004's with the LB7's in them reported the same overheating issues as our LLY's.


Any 2001-2003 LB7 owners out there know what GPM your water pump is rated at? We're dealing with more horsepower/torque than the LB7, it is interesting that the 2004's with the same waterpump as the LLY experiences the same overheating problem. JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

All the LB7 water pumps are the same. I think the LLY ones are the same as well.

The LLY pump and the LB7 are the same except the LLY is a higher volume pump. Thats why we are wondering if it has gained the ability to collapse the lower hose.


IMPROVED WATER PUMP


The Duramax 6600’s water pump has been redesigned to maximize coolant flow. The housing has not changed, and the pump is still internally gear driven to enhance durability and maximize packaging efficiency. Its impellor has been reshaped to move coolant more quickly through the engine.


Go to this link to see the changes:


http://media.gm.com/division/2005_prodinfo/powertrain/index (http://media.gm.com/division/2005_prodinfo/powertrain/index.html). html

Sounds like its possible. It will be great to see what the camera shows! What a great idea to mount a camera and watch the hose!

Sounded good but so far hasn't worked. First I mounted the camera on the plastic "skid plate". Way too much vibration when running. Then I built a 3/16" plate to mount it to and bolted to frame. First test drive not enough light. Mounted a light under there. Now when I am driving all I see is a hose blur. My guess is the camera's optics are mounted in rubber or something. Going to try a differant brand camera. Edited by: RickDLance

Hats off to RickDLance! http://www.dieselplace.com/forum/smileys/smiley32.gif Given the rigid suspension in these trucks it will prove very challenging to mount a camera and get any decent video while moving. Wish ya luck guy! http://www.dieselplace.com/forum/smileys/smiley4.gif


Is there not another way to put some serious stress on an LLY to replicate pulling heavy in hot temps? What about a dynometer(?) that allows the drivetrain to be engaged and a load put on it? I'm likely not using the right terminology for the machine I'm thinking about. Essentially it places resistance on the wheels to replicate pushing a load. This way one can observe the hoses in action. JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

I talked to Justin at Edge about putting it on their chassis dyno to do some tests and they did not seem interested. I would gladly drive somewhere if somebody has a chassis dyno I can use. I have a 60 gallon aux. tank and will run it out of fuel if needed. My dealer mechanic would go with me if I can find one close to Kansas City.

RickDLance, changing out the radiator hoses with those with springs in them is so cheap it would appear prudent to do those first, pull your heavy rig and see what happens. The video might confirm a collapsing hose, but may take considerable time/money to get it right. Are the temps in your area still fairly high to replicate your overheating conditions? JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

I spoke to the SM at my dealer today. I am going to have them change out my hoses this week, along with the radiator cap and both thermostats. The tech mentioned to me that they may not want to replace the hoses with anything other than factory recommended hoses. I am not sure that GM has a wire reinforced hose that is recommended for the Duramax. Does anyone know if this is the case?

Overheating in my trucks does not seem to be dependant on warm outside temp. I have overheated in 58 degree weather, going uphill with a head wind. It also appears to not be consistant. I can pull the same load up the same hill ten times, one time it will overheat and the next it won't. This is why I thought the hose may be the issue. This is also why I wanted to see it happen on a dyno, and be able to repeat it. Just adding the spring and trying to make it overheat may not be as conclusive as I would like it to be. I have also had the reflash done recently and it is possible that it could help the overheat problems with a differant fuel curve. I know both trucks run better and get better fuel mileage now.

RickD, if the reflash has improved your fuel mileage maybe your LLY's were in fact overfueling. I'm curious to see what your temps are next time you pull. If fixed and you are getting better MPG's my LLY is heading to the dealer asap for the reflash.


The times you pulled the same hills without overheating did the engine still get pretty hot, say above 230*? JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

I understand your approach completely Rick, You want to identify the problem and eliminate it so its never a thought again. No more suprise overheating no more wondering if the hill ahead is gonna bite you, the truck just works.

You are also the first to relate that the overheating is an intermittant problem. That is very valuable information, it eliminates static things like hot spots or casting issues and brings it into the realm of moving parts.......things that change position etc. I was under the impression until now that the trucks that overheat do it EVERY time under heavy loads up big hills.

No wonder the problem could make it by GM testing.

As far as the springs go, I would be looking to add the spring to the factory hose. It would be the easiest mod of the hose instead of trying to fab a different hose to replace it.

Anyone notice if the EGT's are higher running up to the overheat condition? Not talking about after the truck is hot, I am talking about the EGT spiking high and then the temperature following the EGT. Lets say 1400 range. Just trying to explore JJ's idea about fueling causing this, especially after seeing GM updating mapping. Maybe there is a spot in the mapping that is whacked and sends the EGT skyward. The guys with the gauges and the overheat problems could prove/disprove this one quickly.

Intermittent overheating and in cold weather definately sounds like a moving part or other restriction, either airflow or fluid flow, thermostat maybe (though I see you've changed them). Sorry if I am being redundant, late into this reading.


Rick if you have a pyrometer, you will be able to find out a lot more than the dealer can tell you. You can get a baseline of temps along hoses, manifolds during normal ops, then when things go wrong, map the same key locations to find out where theings are "cold" or "hot" to determine the trouble spot.


EG, a cold radiator inlet/exit during an overheat means fluid restriction somewhere. If the radiator is as hot or hotter than normal baseline then look at obstructions to airflow, or bad fan clutch (is it on during the overheat)?


Use a pyrometer IR gun and make a written record , $60.Edited by: masterp2

The hose that has been photographed is the cold hose, correct?


Rick, are your tranny temps normal during the overheat?


Edited by: masterp2

.

Glad to see you joining this thread Michael, I have the same view as you on the tranny cooler, I took a hard look at it trying to run down this overheating issue. I determined mine needed a new home, and after searching the forum I read both your thread and the Mike L thread. Let me know when you finalize your cooler, you may save me the heavy research and testing that you have already done.

In the interest of efficiency I would ask you to take a few and read all the posts in this thread to avoid covering the same ground twice, I think you will find some of your initial questions might have been addressed or maybe the dialogue would spark yet a new idea from you.
I think we have done a fair job of eliminating some things.

Anything you can come up with feel free to toss it into the circle! All ideas welcome......

Haven't really focused on the fan clutch but from the desciptions of the situations I would say that vehicle speeds have been more than high enough to render the fan a non-player in this. In my experience much past 30mph (even 20mph in many cases) fans are not needed in direct airflow open grill applications such as ours as airflow at that point is already sufficient.



.

I felt the same way as you on the fan. Strange as it sounds, there is such a pressure drop across the stack that the fan actually does inhibit temperature rise at 70 MPH!


I have seen this over and over, that is, until I moved the cooler. Run the engine and tranny to 215 and 200, fan kicks on (if not sooner) and down comes the engine temp. At 70 mph! So the fan clutch observation is valid, thing is, to my knowledge, if it fails, it is not an intermittent condition, but I could be wrong.


The minimum observations should follow:


Engine AND tranny heat up. For me, Engine around 205 or so, tranny at 190 or more.


Fan kicks on around these temps. It's a distinctive roar. If you haven't heard it, and you have an overheat, likely no fluid is running through the radiator (assuming good fan clutch). Again this can be confirmed with a pyrometer.


I'll go back now and see how much I have repeated what has been saidhttp://www.dieselplace.com/forum/smileys/smiley9.gifEdited by: masterp2

.

Your observations are correct, I have no hard evidence that the stack inhibits flow to that extent, although I have covered the entire thing and still failed to get the truck hot which leads me to believe the cooling system is more than adequate to handle the thermal load of the engine even without external airflow.

My truck never sees 210*, I only got it above that one time on a very long extended full throttle race (story posted before)

The fan on my truck never comes on until the tranny temp nears 200, I would say 190 is the minimum to trigger the fan. If I didn't know better I would say there is a temp switch on the tranny gauge that triggers my fan!!! LOL!

As far as I know the fan is a thermal clutch unit that locks up at 195*, the tranny cooler bathing it in the extra hot air is what trips it most the time, as long as engine temps are 205 or so.

Obviously anyone overheating should have the fan roaring. Anyone ever notice the fan NOT engaged while overheating?


.

Thing that stands out to me and I cant believe I didnt see before are those transmission temps. We have been focusing all over the LLY having a cooling problem but even if it does explain to me those high transmission temps????? The two DO NOT share a cooling system, so your engine should be able to overheat to its hearts content and the alli should be at a normal temp. I think the alli is coming from the back and biting the LLY in the azz. Think about it. The tranny cooler is right there parked square in front and dead in the middle of your intercooler/radiator assembly. How in the HELL can your engine cool if it is being BATHED with a 210, 230 or even 240 degree heat source? I am sure the LLY is disappointed when it sends that 210 degree water up there to get cooled and finds 200 degree or even 230 or 240 degree air waiting for it. Seems to me that would render your cooling system useless. That hot air is also all over our intercooler so there goes some power right there when we need it most, making the problem even WORSE if you are towing at the time.





I was tickled pink to find I wasn't alone in understanding the downward spiral phenomena. I could not have said this better. Because of it's diminuitive size, most conclude it couldn't be that big an impedance to effective engine cooling, et al. It is. Tx, I love you.

.

Yeah but I missed the tranny line sneakin into the radiator on its way, it was dark when I was under the truck.

The location of the tranny cooler is just stupid, it is obvious in the factory location that it does nothing but hurt the A/C performance as well as the intercooler and radiator. A more efficient cooler in the same spot would only serve to degrade the other three further. But that's another topic.

I also abused my truck seeing if the alli could in fact drag on the cooling system, and although I am sure the thermal drag of the alli doesn't help, the cooling system seems to have plenty of ability to handle the extra load the alli can add even under abusive conditions.


.
Edited by: TxChristopher

.

A more efficient cooler in the same spot would only serve to degrade the other three further. But that's another topic.





But I'm glad you said it!http://www.dieselplace.com/forum/smileys/smiley32.gif


Someone on this board is getting ready to sell one. My only hope is that he refuses sale to LLY's. I think there is going to be a few more visitors to this thread soon.


A good point you raise is the ability of the condenser to accomodate the cooler. That's also part of the problem. Higher delta T off the back of the condenser then deteriorates the intercooler (higher inlet temps=less O2=power loss=more power needed=yet more heat generated) which then deteriorates the heat removal at the radiator, because of unusually high air temps and chockingly slow mass flow rate of air passing over the stack.


I have said forever that we need to think in terms of "operating envelope", not temps. It is possible to overheat anything at 58 F, and air temp is only one factor in defining the operating envelope. Simply it matters not if fluid doesn't pass through the radiator. You will overheat in 0 F. Conversely, without air flow (we are always going slower when we boil) the fluid rate of flow loses importance.


Expanding the operating envelope involves all the variables that can influence heat generation and rejection (assuming there is no obvious killer like stuck thermostat). Air Temp, mass air flow across the heat exchanger, fluid temp, fluid mass flow rate the key ones. Define these and you will find where heat rejection improvements can be had. Tires, chips, fluids, headwind, add heat to a lesser extent. Then the biggie, load, driving up boost and IC temps for another thermal design failure. Higher IC temps result in higher filtered intake temps, as underhood temps rise. As we all know, cold combustion air is our best friend.


My conclusion was that the stack is ridiculously congested with high efficiency fins, and amounts to a brick wall if enough air cannot get across it. It is saturated past the point of allowing sufficient air through, and if air cannot get through, death. That begins at the cooler, well grill actually. If a fan coming on at 70 MPH cools things down (significantly increases air mass flow rate), there is some serious pressure drop enroute to the radiator.


6 months ago I posted an article asking for help on this crazy loud fan, when I learned how it operated, before concerns of overheating developed. I thought "how stupid is that". To cool an engine based on the final T of the air coming through, and not fluid temp (like everyone else does). But if that fan doesn't kick in soon enough, game over to a possible thermal death spiral. Get rid of the 230 degree cooler and one spiral trigger is removed. Research illuminated the presence of newer EV, electroviscous, fans that are reliable and are triggered by sensible variables, trans temp, coolant temp, speed, etc. I even found an article that says they are suppose to be on 05 trucks. Haven't seen it yet.


But as soon as that transmission gets hot, plan on getting over the top soon or turning off the AC, because it has much more of an impact on everything else than ever previously thought. It just took a hotter truck to illuminate the failure in design consideration. I guarantee there is an engineer somewhere looking for a clown job now. To run fluid thru the radiator to cool it (heating coolant), then to a heat exchanger in front of the radiator (which then heat's up the radiator!!!!!!), that is a Bozo move. Can you say LOOPED THERMAL RUNAWAY?http://www.dieselplace.com/forum/smileys/smiley7.gif


Not saying I have the solution to your problems, but if you are at 40 mph pulling 15K up 8% on a 98 deg

Boy that sure sounded like a lecture, how embarrassing.

IMHO, trying to chase the collapsing lower hose theory is a waste of
time. Springs were eliminated from lower radiator hoses for two reasons
- cost - and the fact that water pump suction will NOT collapse a lower
hose on a modern (pressurized) cooling system.

.

Assuming that the stack is the breaking straw and the fan is the saving grace, running a higher temp thermostat would move the heat to the back of the stack and cause the temperature controlled fan to come in sooner/earlier. This is also assuming that the fan has the ability to hold the line from there. Faced with such a problem I would eliminate the clutch fan completely in favor of thermostatic controlled electric fans. That way I benefit from regaining the huge parasitic loss needed to drive that big honking fan in the first place. This is why I ran electric fans on my race cars.

However I am not convinced the stack is unable to cope. It may be a poor design but still have the ability to function and do its job. In my tests I proved the system can cope with the fan and NO external airflow.

How did you verify airflow through the stack (exiting the radiator) at various speeds? You would have had to have a camera monitoring your weather station and the fan disabled to obtain that data.

The reason I ask is because when my fan does come on all I have to do is accelerate slightly and it goes off. This may have more to do with the fan pulling more air due to increased engine speed and also more cooling due to higher water pump speed than increased airflow through the stack, I was attributing it to the airflow more.
Seems to me if there were no flow at all across the stack then the fan would always run once the engine were up to operating temperature, but it doesn't.

Anyone reporting overheating and the fan not active leading up to and through the overheating? The fan should be coming on and staying on around 210 degrees engine temps I would think. It would seem obvious but you never know :)



.
Edited by: TxChristopher

.

The collapsing lower hose may well prove to not occur. That's a given.

The springs were not eliminated due to pressurization of the system. They were eliminated due to better design hoses. On the flip side, springs were added to prevent collapse due to pump suction on PRESSURIZED systems for many years.

Nobody is saying it is the problem for sure but with a new higher flow pump and no spring it is POSSIBLE.

At this point we are exploring ALL possibilities until the solution appears, whether it is blockage, fan, stack design, hoses, bypass port, over fueling, or whatever it may be.

Any ideas you have on what the problem could be please post them.....

.Edited by: TxChristopher

Is there a possibility that the quality or composition of the diesel fuel itself could somehow adversely affect engine temps? Additives, blends, etc.? TX, you said no ideas are bad ones! JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

This is my first diesel and I was not used to an engine running safely at 210. The night I picked up my truck, I saw the temp and called the dealer the next day. The service guy was asking the tech about my temps and I could hear the tech tell him that the system was not designed to kick in the fan until http://www.dieselplace.com/forum/smileys/smiley34.gif 225 http://www.dieselplace.com/forum/smileys/smiley34.gif degrees and 210 was fine.


If this is true, I am uncertain how or where they are picking up the temp reading to activate the fan. My temp has never exceeded the 210 mark. Actually, it runs one tick under 210 even in 100 degree heat with the air running full blast. However, I have heard the fan kick in, but it has always been while pulling a big hill.


My air conditioning is not as cool as it should be in stop and go and at slow speeds, which tells me that there is insufficient airflow across the condenser and the Alli will run right on up to 200 (I have followed masterp2's thread closely for a solution to this http://www.dieselplace.com/forum/smileys/smiley4.gif) but the engine never budges over the 210 mark.


Hope this helps.


Edited by: Chisuzu

.

The fuel causing the problem is possible JJ, although coming from a racing background it is too lean a mixture that causes high temps, not rich or over fueling. Diesel isn't the highest refined fuel although it has nearly twice the thermal energy as gasoline. The thing is that of all the possible causes we have been looking at fuel would be the easiest to nail the blame on because it would show up as very high EGT. The only way for fuel issues to cause the problem would be because it raised the combustion temp or even continued to burn upon exhaust, either way the EGT would rat it out quick.

That's why I asked if anyone with the overheating problem has gauges, the EGT would rise first and there would be a delay in the heat transfer before you would see the overheating.

Chisuzu: my temp tuns about one needles width below the 210 mark. It never really budges. The fan is a thermostatic clutch fan, it usea a viscous fluid to engage the fan when the temperature that reaches the clutch is 195* (if that number is wrong someone speak up). The temperature of the radiator and the rest of the stack ahead would be higher than the air that reaches the fan clutch but no matter what they are the fan comes on when it gets to 195* itself.

Test #4 is fast approaching and it will involve the fan.......

Keep pouring in the ideas.......

.

Assuming that the stack is the breaking straw and the fan is the saving grace, running a higher temp thermostat would move the heat to the back of the stack and cause the temperature controlled fan to come in sooner/earlier. This is also assuming that the fan has the ability to hold the line from there. Faced with such a problem I would eliminate the clutch fan completely in favor of thermostatic controlled electric fans. That way I benefit from regaining the huge parasitic loss needed to drive that big honking fan in the first place. This is why I ran electric fans on my race cars.




For me higher temp stats do one thing, increase heat exchange efficiency for the engine cooling system. The higher the temp of fluid, the more BTU's will be removed by the air flow, at all air flows. And yes, it should bring the fan on sooner, yuck.


You won't find an electric that can pull the air you need to on this 8-blade cropduster, you would need a 10-15HP motor, and even if you did you would need 50 amps to run it. And what does that mean to the motor, right, 15 HP alternator load, same problem, the motor has to generate 15 more HP (and heat byproduct) that doesn't make it to the road!


Not saying electric fans are a bad idea, I like them, they have great uses and do find homes in applications that benefit from low pressure drop stacks. They are smart, but inherently flow limited though compared to the windtunnel we have/need.


"However I am not convinced the stack is unable to cope. It may be a poor design but still have the ability to function and do its job. In my tests I proved the system can cope with the fan and NO external airflow."


You are proving my point. The fan pulls better than a 70 mph airstream pushes (but more importantly, poor system design requires that noisy power siphoning blowhard) . In your test that air came from somewhere! No external airflow? BTW, A 55 mph stream is 22 mph right behind the radiator, fan clutch disengaged (but spinning). It wasn't easy to get that measurement. No camera required, it logs average, min and max data, it can graph over time also. I wasn't saying there is no flow, it is terribly reduced due to 8" thick stack of metal fins. The pull design of the fan is the saving grace, and it will pull that air from any crack or orifice in front of the radiator, regardless of what covering is placed on the front. True the fan helps the radiator most, but if all the fan can do is pull 140 degree air (from 3 stages of heat transfer) then efficiency sucks, and of course you have to move MONGO air if it is hot air, 15 HP worth of air.


The reason I ask is because when my fan does come on all I have to do is accelerate slightly and it goes off.


Me too. It is because air running across the stack slower will be hotter that if it runs across (or pulled across) faster, the hotter, slower stream activates the clutch, the lower temp of the air that follows, and the rotational speed of the fan disengage it. Ever notice that the air that comes out of the ac vents is colder on low speed. Stop and Go traffic=fan on then off, it's temperature (bimetal strips) driven. JMO, the system should not have been designed to be needed at high speeds, where you need the power most, not 15 HP reduction and MORE heat. I'd like a fan that rotates faster at low RPM's and is defeated at higher RPM's, like the EV fans reportedly do. Come on with AC activation, etc, a smart design. But even that doesn't compenstae for excessive pressure drop. The only thing that does is big fans or removing something.Edited by: masterp2

My air conditioning is not as cool as it should be in stop and go and at slow speeds, which tells me that there is insufficient airflow across the condenser and the Alli will run right on up to 200 (I have followed masterp2's thread closely for a solution to this http://www.dieselplace.com/forum/smileys/smiley4.gif) but the engine never budges over the 210 mark.





Come down to Phoenix on a 110 day and pull 12K up I-17. That will budge it.


BTW, the biggest impact to the AC is the 200 degree cooler sitting right in front of it. Radiative black body, plus a bunch of hot air spilling on it, and the kicker, the fan does little at the front face of the condenser, 10" away.


If you haven't done so already look at the TSB on this.Edited by: masterp2

.

Excellent info as usual Michael. Post that TSB, you already have the info share it!

Not that I don't believe everything you said, but I like to really run things down and especially real world testing if possible. I would also think that 22mph of air across the radiator would be enough to maintain cooling, of course I don't know for sure but I will find out. That's assuming 55mph..... I take it the airflow is greater at higher speeds (the overheaters report 65 or better).

My next test will be all about this fan be sure of that.

Now for my monkey wrench off in your gearing:

Laying the blame on the stack is all great and good, but how do you account for all the zillion LB7's out there that have the same cooling system (and stack) as the LLY's but the LB7 owners seem shocked that the LLY's get hot much less overheat. We can't palm it off on the EGR either because people have blocked its flow and although they gained a small headstart against overheating they still overheat the same. Also if the fan is the keeper of the temperature then even if it came in 10 degrees or 15 degrees late to the game it should stop the overheating and begin to reverse it.

I am with you, the stack sucks......but it has been around without issue for a few years now.....

The problem is LLY's overheating intermittently, and if you are saying that's because of the fan not functioning then we should be able to "run this to ground quickly" as JJ would say.


.

masterp2 wrote:


Come down to Phoenix on a 110 day and pull 12K up I-17. That will budge it.


http://www.dieselplace.com/forum/smileys/smiley36.gif Thanks for the offer, but I spent 15 years in central Florida sweating my azz off. I like the nice cool mountains, so I'll pass for now. Come winter and I might be changing my tune though! http://www.dieselplace.com/forum/smileys/hihi.gif


BTW, the biggest impact to the AC is the 200 degree cooler sitting right in front of it. Radiative black body, plus a bunch of hot air spilling on it, and the kicker, the fan does little at the front face of the condenser, 10" away.


I believe it. The fan clutch on my S-10 didn't do much either. I switched it to electric that was not only thermostatically controlled but was also wired into the AC compressor so whenever the compressor turned on, the fan turned on to flow air for the condenser. In central Florida, you need air year round and after I added that fan it would freeze you outta there. The tranny cooler on the little truck is at least 2.5 times the size of the one on the DMax and its strapped proudly to the front of the AC condenser. I towed my boat with the little guy all over the state looking for the ever elusive LMB (large mouth bass) and never had another heat related issue. I even towed it all the way up here and had no issues, other than slowing to a crawl on these mountains, hence the DMax. http://www.dieselplace.com/forum/smileys/smiley4.gif


I was just tryin' to pass on that the dealer told me 225 before the fan kicks in. This would fall right in line with what you were saying about too little, too late.


Sorry if the info is wrong, just what they told me and I thought it was worth throwing it out there.


Tx: I gotcha! So maybe the 225 figure (for the stack) isn't too far off? Did you pull that info about the fan outta the Helm? I have yet to explore all 5 phone book sized volumes! http://www.dieselplace.com/forum/smileys/smiley3.gif I couldn't believe my eyes when that thing showed up! Thought it was part of my gear set! http://www.dieselplace.com/forum/smileys/smiley4.gif


masterp2: Love that tranny cooler! http://www.dieselplace.com/forum/smileys/smiley4.gif

The door sticker will get you your build date. It would be nice if we could tabulate the people who are doing fine and the ones that are over heating (or just getting to hot) and see if we can find some similarities.


My 2004 Durmax was manufactured in May of 2004. I have significant overheating problems. Fan clutch was replaced but did not solve problem. I pull 12000 pounds and a long steady pull will easily run the temperature to 260 degrees. I have had the truck to three dealers and no one knows how to fix it. Looks like it is lawyer time. To bad because otherwise it is a good truck and the transmission is a dream to drive.

.

Chisuzu: I would say the answer to the 225* question is more of a no than a yes LOL!

The reason I say this is because the fan clutch is wholly dependant on underhood temps. If you let the truck sit the engine will go to about 205 or so and the tranny will be like 160 maybe 170. The fan will still come on because the temp under the hood is higher than the stack. Of course when you are moving the stack passes some hot air back to the fan clutch and helps the fan come on, but still this happens when engine temp is about 205 or so and tranny is 190.

Guess my point is that there is no stack temp that triggers the fan, although obviously the stack can have a lot to do with that.

I don't recall where I got the 195* figure, I am flying a disclaimer on that til I can find it again, generally though memory doesn't fail me too badly!


.

Can the stack be seperated at all. If only an inch between each componant I wonder if this would decrease the resistance to air flow - or perhaps it would cause turbulance. I also considered installing a push fan on one side of the radiator to supliment the system and hopefully keep the engine fan from running in stop and go traffic. The grill on my GMC does not have the clearance for the fan though. The Chev's I noticed have more grill clearance, so a push fan should fit.

.

Laying the blame on the stack is all great and good, but how do you account for all the zillion LB7's out there that have the same cooling system (and stack) as the LLY's


Also if the fan is the keeper of the temperature then even if it came in 10 degrees or 15 degrees late to the game it should stop the overheating and begin to reverse it.

The problem is LLY's overheating intermittently, and if you are saying that's because of the fan not functioning then we should be able to "run this to ground quickly" as JJ would say.





The TSB is for the early LLY's accumulator, the effectiveness of replacing it is dramatic. I just got my truck back and I feel the capacity to cool the cab is up 30-40%, just a WAG. I had 40 degree air on auto, after 15 minutes, on a 96 degree afternoon, I couldn't get under 50+ before this.


As for the LB7's, hmmm. Here's one, tranny cooling! the LB7 tranny is poorly cooled, much of the heat that is now dissipated from the cooler in the LLY was retained in the LB7, many posts address the LB7 complaint on tranny temps. The remedy for the LLY was an increase in fluid flow rate, but the downside is those extra rejected BTU's go into the stack. Yes, emmissions have had an impact, something about running hotter=better burning, heck the ECM code has a lot to do with it, just ask Edge. No doubt GM has turned up the heat to comply with emmisions requirements. BUT, I haven't fully cracked that question, A GOOD ONE. Perhaps it is as simple as the more effective tranny cooling.


I hear what you are saying about the fan killing the spiral progression, it just doesn't seem to. Yes it cools, but the progression is too far along it seems to me. Once the fan kicks on, power is lost, not only in spinning the fan, but because of inneffective intercooler operation. I believe the truck enters a region (evelope) that recovery is not possible, because of the decaying power curve. If this is true, then fanning sooner, could be a real solution. A little far out? Maybe. But effective cooling (or lack of) of the intercooler is an important part of this I suspect, it does elude because we don't have a gage for it.Edited by: masterp2

rdesjar


where do you live? details?

I do wonder if some fan clutches kick in sooner than others. Mine is on the safe side I would guess (it was a nuisance before the cooler change)


Some parameters to look at: You should hear the fan come in if the tranny reads 200 OR the engine temp (edge) reads 205 (215 if traveling a good clip) If it waits much longer than this, say 220 engine and 210 tranny, then the intercooler is just sucking wind (a humble opinion).


Intercooling is a beatiful thing. the turbo compresses combustable air, which heats up in the process (good thing!) then travels across the intercooler in a heat exchange process to be efficiently cooled, then re-expanded for a DRAMATIC adiabatic expansion cooling. An intercooler that suffers reduced efficiency because of low air flow doesn't get very cool=hot intake temps and ultimately lower power output from the ol dmax. (Nothing like COLD air to perk up things.http://www.dieselplace.com/forum/smileys/smiley2.gif) Same heat generation though. Step on the pedal (because of the lower power available) to keep it goin up the hill=more heat.


I'll bet there was even an LB7 or 2 that overheated.





Edited by: masterp2

masterp2, there were a few 2004 LB7 owners that had identical overheating issues. Seems like older versions of the LB7 had heating issues when mods/juice was applied.


The redistribution of btu's from the allison to the stack is interesting, especially given the radical drop in temps you experienced on your truck after the mod. Need to strap some serious weight on your truck and hit the hills! Any chance of that? JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

What about the 4500 or 5500 series truck? Are they running the same lly motor as our 2004.5? And what stack of cooling do they have?

Well, this is all great and good so far but right away we had someone chime in and say replacing the fan clutch did nothing. Add in the fact that the majority of LLY's that tow heavy have no problem at all and I have to doubt that the stack is inherently overwhelming the cooling system.

If it were the stack causing the problem then 100% of the LLY's would fail towing and that is just not the case. Don't forget russmonsters truck, normal tranny temp but overheated engine. It wasn't the stack that got him there.

I didn't have time today to run test #4 and until I do I will hold on further judgement of the fan and the ability of the stack to defeat the LLY. I agree that it may not be the most efficient design but nothing I have been able to do so far has revealed anything but a system with capacity to spare. My next test will reveal the ability of the cooling system versus 'da stack' and its compadre 'da fan'. From what I have seen so far my money is gonna stay on 'da system'


-end transmission-


.

JJ


all I have is a small boat, I'll be glad to hook up a volunteer.


Tx


I said a lower temp fan clutch, that would require research outside the dealer's bounds. But it's just an idea to be tried before condemning.


If localized superheating is heating the coolant to a point that would cavitate the pump, then that would be an irreversible rapid progression also. Local hot spots should be factored into cooling system design, resulting in a system that keeps fluid cool and moving.


I completely disagre with your statement that 100% should fail towing if all LLY's share the same weakness. I towed with the stock rig in 116 degree heat and didn't overheat. Not everyone is overheating, and some are part timers. Everone has a different load, different mods, different day, hell, everyone has a different number of dead bugs in the condenser. I don't care bring them all here and with a 12K load I will overheat everyone of them, I guarantee it. My contention is that the LLY has overtested it's thermal envelope. As soon as it develops more heat than it can shed, it is running outside that envelope (on borrowed time as the saying goes), the LLY finds those parameters with a higher fraction of customers. The precautions put in place are no different than the LB7, that is correct. That leaves me with what others believe also, the LLY makes more heat. Of course it would need to to support the higher power numbers GM posted along with better tranny cooling. Add 70 more HP with the edge, after killing a few ponies with bigger tires, and my truck is not what GM designed 5 years ago. If I were looking for overheating, I'd go to Phoenix or other place with 115 air temp and 8% grades, not wyoming. That air temp closes in fast to the 200 degree water you are trying to cool with it. The diff in cooling efficiency between pulling on a 60 degree wet day and a 115 deg day with 6% humidity is like 60%. The fan won't compensate for that, it runs at 1 speed. You have to reduce heat, higher rpms, turn off ac, mist the stack, etc.


I heard it said once you can overheat anything on any day, and I believe that. I also believe that all overheating starts at a local hot spot and develops from there. If steam gets anywhere near the pump inlet, then it will just stop, nothing can be done then except to shutdown and wait. So higher temp stats would not be my favorite solution, it reduces pad. Even if a lower temp fan clutch works, it would annoy the crap out of me.


I saw a 1999 article that described the dmax introduction, as having the cooler mounted under the radiator. It never showed up that way for some reason, hmmmm. But I will say from experience, it expands that thermal envelope, it works, effectively increasing stack heat rejection capacity 30% (estimated including tranny heat rejection), and the peace of mind....


If you haven't done it already, get a look at the dodge, take some measurements, grill area, total fin area, location of tranny cooler, and compare to GM. GM went too far IMO, they shrunk the nose to make make it market as the wifes vehicle, and then ignored the stack area in the development through the years. Maybe this years truck got a slightly less efficient radiator from an alternate vendor because of pricing issues. So many things we can't put a finger on are possible to just put the truck over the perverbial thermal edge. Every design change means consequences that only a limited % of the population will test. I believe GM is now seeing this fallout as a result, and also remember, that only the people with the problem are here trying to solve it. The vast majority still love their trucks pulling jet skis on an 80 degree afternoon, they don't care (or know) that they can't hook up a 5th for an 10 mile 8% pull on a 110 deg day. They are watching football, not

.

The grill was also around with the LB7, again, where are the LB7 guys at complaining about overheating? Since the tranny had overheating problems with the LB7 and the stack is the same why don't batches of LB7 owners come flocking crying about overheating? The ten horsepower change is not significant enough to be causing this problem either, it is common to see a ten horse variance from vehicle to vehicle. The LLY has a higher flowing water pump that should be an advantage over the LB7. The EGR and CAT are not new but the EGR cooler is, but people have blocked it as a heat source so if anything it is transformed to HELP the engine cool. The differences between the LB7 and LLY are just not great enough to support catastrauphic cooling system failures these guys are reporting.

I wish I had time to come over your way because I don't buy 12k overheating my truck. There are plenty of other LLY owners who would dispute 12k getting anywhere near straining their trucks. I do stupid crap with mine like drag racing it REPEATEDLY on 98*to 100* days. With 5 people on board. Bed full of gear. TOWING the boat loaded with stuff. The trucks I am messing with are typically older dodges or fords that are unloaded, but I know they don't have a lot of power so it makes for a funny race, a big heavy 4x4 crew cab diesel towing outrunning an unloaded truck or at worst for me staying close enough that they are still embarrassed. After they try maybe the 5th or 7th time IN A ROW they generally give up.

My cooling system isn't really getting a break during this, I am asking the truck to give me everything it has, not just trying to maintain a towing speed, and then I am jamming down the brakes and taking away the airflow except for the fan because there is a red light coming. Of course I stall it up so I can compete when the light changes cause the race is on again.

Even under this type of condition the temp never gets out of control. Not anywhere NEAR it. Does the temperature rise? Yes, but not much. The tranny runs to 200 maybe even 210 but the engine never gets much past 210, 215 at worst and I find that to be more than reasonable.

How you can disagree with the statement that if 100% of the LLY's share the exact same weakness they would fail yet say some can escape that weakness makes no sense to me. These guys that are overheating are saying it comes on so fast that there is nothing that can be done to prevent it. Each truck may have slight differences, some may have less bugs in the condenser, but if the design is the problem and the problem is so overwhelming as described by the overheaters then NO DMAX should be able to accomplish the tow. Slight differences either way are not going to stop an overwhelming problem.

Remember we have STOCK trucks towing well under the parameters designed by GM and they are overheating with ease.

Not knocking you personally Michael, so don't take it that way. I have suggested replacement of the radiator as well. Thing is a radiator that doesn't flow or is plugged or otherwise doesn't function as a heat exchanger is not an intermittent problem. RickDLance tows for a living, his trucks are stock and he tows the same weights over the same roads under the same conditions sometimes with no problems and other times with disasterous results. That's too great a swing for a static system that I agree has a certain operating envelope. The nature of that envelope means its response should be predictable.

Anyone live close to masterp2 that has an LLY that does what it is supposed to do wanna go drag his 12k load around to show that an LLY dmax/alli isn't just some fake piece of crap faker wanna be that GM is somehow covertly palming off to us?


.

Well, I've shared what I think. With overheating now a household word for the LLY, and winter approaching....maybe next summer with break-in, there will be fewer problems.


Intermittent burping in cold weather....stats, pump, bypasses, moving parts. But overheating is by it's definition intermittent and difficult to reproduce exact conditions from incident to incident, too many variables, right down to the weight of the boot on the accelerator..Overheating in 58 degrees presents a mystery if the usual components are working. Turn off the AC, does that help? If so, obviously design is at issue!


Correct me if I'm wrong, the vast majority of problems are the severe conditions, 3H's, hot, heavy, hills.

If an engine is overheating rapidly and intermittend at the same time
it cannot be the radiator (its not intermittendly clogged) and I don't
think the no. of bugs in front of the radiator has anything to do with
it.

It MUST be something like a sucked closed lower radiator hose which
will not happen all the time. The casting of the engine or waterpump
stays all the time the same, if there is a problem its there ALL the
time.



Its more like a heart attack, very rapidly blocked flow of vital fluid
IMHO. I still support Tx idea about radiator hoses, so somebody should
really change it and see. I have no trailer and live on flat land - I
cannot test it. I have noticed that it takes forever to warm up that
engine. (EGR disconnected). The cycling of the thermostats is clearly
visible on the temp gauge. Its not exactly cold here in Louisiana and
there is still a big reserve before the temp gauge even hits the 202
deg mark where it stays. I have never driven a car or truck with that
kind of cooling capability not even in Saudi Arabia in the sand dunes
(Toyota Landcruiser - which had the best cooler design of any truck at
that time). For me it looks the cooler design of the actual dmax is
good enough - if it works as specified and designed. Like masterp2 and
others said any truck will overheat if the right load and temp
combination exists.

Just my 2C

I talked to the area rep to GM yesterday and told him my story. He had all my info from the shop visits. He will get back to me hopefully early next week with some news on how they are going to fix the truck.... When a fix is found I will be surprised if it isn't in the radiator. It is too small compared to my 2000 power stroke and can not recover once the heating begins.

If the radiator is still the same than with the LB7 why did they not
all overheat? Its not only the size but design of the radiator,
flowrate of fluid, size of fan and fan speed....and also engine design
and efficiency to dissipate the heat.

I personally don't believe that the problemis intermittent. I believe that the conditions might be intermittent. It would be very odd if this many trucks had the same intermittent problem. I know there are a lot of guys on this board who report not having a temp problem while towing, but I still beleive that all of the LLY trucks hooked to 12K pulling from El Centro to San Diego or the Grapevine, will see temps in the 230 range. Now, that may be acceptable to some, but not me. The guys that are actually losing coolant and seeing 260 are probably pulling more than 12K or with a big wind resistance. Maybe guys on this site will find the problem, I am hoping. Who is responsible? GM. I think that our best course of action is uniting in a petition. Every time I have talked to GM, they say they don't have record of this being a problem.


I suggest someone who is willing to take the time and is out going (JJ) could start a new thread with no discussion, just a place to post your VIN, name, phone number, address and problem.


Anyone volunteer? I would, but I might not have the time to follow through.

.


Well, the hose thing is still only a theory, I don't have any hard evidence it can happen. It only became suspect when combined with supporting characters like the new high flow pump combined with a restrictive thermostat and no lower spring. Maybe the new pump is just prone to cavitation. Maybe it runs the coolant thru the system too fast. If my truck were one of these overheaters and I had a stealer replacing all of the other components I might talk them into putting the LB7 pump on just to take a shot at it. Maybe the new pump has nothing to do with the problem at all.

The only other working theory is the bypass idea. I am gonna buy a gasket and disassemble my housing and see what's in there. Might try running the truck with that bypass open to see what impact it has. I have tests coming for the fan too. Of course I am not out to ruin or kill my truck, I just am trying to see what could be causing this overheating problem.

Still with the problem being intermittent its got to be some moving part, something that changes states. Hot spots, blown gaskets, and pluggage issues are static things they are always there. A crack or leak CAN be intermittent without pressure testing because it will slowly allow coolant to escape and the truck may not overheat until that big load is put on it. A pressure test should reveal cracks, leaks, or bad gaskets. Even a half ass mechanic can find those things.

If the problem is not intermittent and is a design flaw due to load (12k and steep hills like exford is saying) then we are chasing ghosts. I don't have the problem so its hard to gather enough info to close in hard on it. I have come to respect the cooling capability of the truck though and am now moving into crippling the "moving and changing" systems to force an overheat just to try and get a whiff of what it would take to make one run hot.

I have been up the grapevine before, though not towing. Lived in Bakersfield and we had a cabin up at Bass Lake. Yes it is a pretty healthy climb but still.......


.