towed the 5er home from the desert yesterday as its been in storage out there for the last 6 months. went fine for the first half of the trip, temps in check, power fine, ac blastin, no problem. after about 60 miles, i hit the 10fwy east of palm springs and noticed my temps started creeping up, it took quite a while but once it was almost to 230* and the fan came on to bring it back down, it had no issue racing back to the temps instead of creeping back up. 220-230* coolant temps on flat ground with a tail wind bothers me, trans was gettin to the 205* area before i made a pit stop. outside temp was 93*. my concern is that ive towed this same route MANY times with my trailer and its the last 3-4 trips that ive been noticing the much higher than normal temps. i used to tow thru there when it was 120* outside and the truck would only go over 220 if i was pullin a long heavy grade at 55-60mph. now the power feels down as well, ive never had to put the pedal on the floor, but it seems to be commonplace now, wtf? no codes stored, engine sounds normal, fuel mileage normal. i had the thermostats and coolant replaced this past september when the hotter than normal temps started showing up. it seemed to help then, but not now? ive cleaned the front parts of the cooling stack, thinkin ill have to seperate them and get in between now? coolant level is fine, hasnt dropped at all. at least the ac is still frosty cold when its runnin hot....:rolleyes:

any thoughts?

whatup elcamino.???

anyway....have you......

changed your coolant?
changed tranny fuild

the only time my 120k dmax had really hi temps was during a freak wind storm comin home from Dumont

http://www.youtube.com/watch?v=vZs9IC4qqOE

forgot to mention truck has just about 73K on it now.

what up cheese? coolant was changed this past september when the t-stats where done. havent changed the trans fluid yet, but the spin on filter is replaced every 10k miles

forgot to mention truck has just about 73K on it now.

what up cheese? coolant was changed this past september when the t-stats where done. havent changed the trans fluid yet, but the spin on filter is replaced every 10k miles

im sure i would have noticed the difference anyway, but when i changed with transynd, my temps rarely creep up past 160 now.

easy to do...next time you change the spin on filter, drop the drain bolt...and have 2 gallons of transynd on hand...you can find it at your local alli dealer

as long as the fan is controlling the temps (IE, the temps come down as soon as the fan engages) then everything is operating normally and I wouldnt worry about it.

Its when the fan cant keep up (ie, fan is fully engaged and roaring away but the temps continue to climb) that you should start to worry.

205* is nothing for an allison. They dont care about being run hot.

ben

Clean the fins in the radiator and trans cooler, also check between the condenser and the radiator for trapped trash. Have a good day.

well, im very much frustrated with the truck after towing a 20ft pull behind toy hauler that weighed 8-9Klbs last night. outside temp was 95-105*, coolant was heatin to 225* on level ground or very slight hill with a slight headwind. fan would come on and the temps would come down VERY slowly to 210ish. once i hit the 6% grade (that ive towed MANY times with larger trailers at 55mph and have to be light on the pedal since it will charge well over 60), the truck was having absolute hell trying to keep from falling under 50 with the pedal flat on the floor. once the temp hit 240* i stepped off the pedal and rolled along at 35 with the fan HOWLING temp dropped to 235* and stayed. trans was pushin 220*, EGTs at 1280-1300* and boost at 18psi when on the floor in 4th gear. dropped to 3rd and the EGTs went to almost 1350*, thats when the engine it 240* and i said thats enough.

several weeks ago i took the front end apart and cleaned the cooling stack as best as i could and alot of stuff came out. i also put in a bottle of BG super cool after the last hot run session, but that apparently hasnt done crapola. this is really starting to bum me out, this truck used to pull like a freight train and kept its cool no problem, but now im almost expecting it to blow the heads thru the hood or throw all its coolant on the ground whenever i tow anything :(

HELP? PLEASE!

yeah man that doesnt sound right, maybe its time for the dreaded trip to the stealer :(

thermostat sticking?
air filter plugged?
cat converter starting to plug up or some sort of other exhaust restriction?
intercooler boot blown off or leaking?

thermostat sticking? both replaced september 2009 when i started seeing higher temps than what im used to seeing on my display
air filter plugged? replaced about 25K miles ago. its due as i replace it every 25K. however, the truck hasnt run hot like this at 25K and 50K miles
cat converter starting to plug up or some sort of other exhaust restriction? possible i suppose, i do get on the pedal regularly to clear it out tho. its 4in straight pipe from the cat back
intercooler boot blown off or leaking? i checked the intake system for anything amiss but everything looked fine

if the intake manifold is becoming caked on the inside with oil from the pcv system and soot from the egr creating the creosote (sp?) buildup, could it be contributing?

I really doubt the buildup in the intake would cause this. Im leaning towards the air filter being plugged since you said it has been in storage for the last 6 months. I have seen some strange places that animals have made nests and carried stuff up into.

I really doubt the buildup in the intake would cause this. Im leaning towards the air filter being plugged since you said it has been in storage for the last 6 months. I have seen some strange places that animals have made nests and carried stuff up into.

the truck has not been in storage, i drive usually a couple hundred miles a week. my 5th wheel toy hauler was what was in storage.

additional stuff i just thought of, ive also noticed that when accelerating from a stop up to highway speed withe the trailer hitched up (and i dont mean like freeway onramp accelerating, just driving normally up to speed on a road) ill see 15-20* increase in coolant temp very quickly. could the water pump have a problem? :confused: i can say that when the truck is not heating, it pulls fine. it isnt until the temps go over 220 that the power starts really falling off

El Camino Man, I hope you've found the problem by now, but for what it's worth, I had some of the same symptoms regarding power and discovered it was simply my fuel filter. My truck is an LLY so running hot is par for the course, but what you described is even worse than mine. Good luck.

Sounds like your knocking the obvious things out. Time for a pressure test. We don't have any evidence that the manifold being clogged from the EGR is causing your problem so I would exhaust other things first. Water Pump or just for the heck of it change the thermostats again. Head gasket is a possibility but other symptoms should show up first.

CaminoMan, is this heating problem only when towing your 5vr then? Have you done any maintenance to the wheel bearings or brakes lately to the 5vr make sure everything is working good? Although the last info. you wrote makes it less likely it's the 5vr?

Sounds like your knocking the obvious things out. Time for a pressure test. We don't have any evidence that the manifold being clogged from the EGR is causing your problem so I would exhaust other things first. Water Pump or just for the heck of it change the thermostats again. Head gasket is a possibility but other symptoms should show up first.
im going to have the guys at the shop take a look at it next week and get their take on it.
CaminoMan, is this heating problem only when towing your 5vr then? Have you done any maintenance to the wheel bearings or brakes lately to the 5vr make sure everything is working good? Although the last info. you wrote makes it less likely it's the 5vr?
i went thru the wheel bearings and brakes on the 5th wheel at the end of last year so i know that stuff is all up to snuff. up until the other night when towing the 20ft bumper pull toy hauler, i was only experiencing it when towing the 5er. now it just seems if i tow anything other than a flatbed trailer it heats :(

what is the proper coolant to water ratio for these trucks?? the tech who did the thermostats last year and drained the coolant, refilled it with like a 75/35 mix of coolant/water....!! im used to 50/50 out here in so cal and thats VWs required mix as well

what is the proper coolant to water ratio for these trucks?? the tech who did the thermostats last year and drained the coolant, refilled it with like a 75/35 mix of coolant/water....!! im used to 50/50 out here in so cal and thats VWs required mix as well

I believe that it should be 50/50 because the coolant does nothing for cooling in fact, it does the opposite, It's the water that does the actual cooling . the coolant is there to protect against rust and corrosion and as a anti freeze in the winter. what you could do is drain and put straight water in to see if it heats up again and if it doesn't then that was the problem but, I do not suggest running it that way for long cause you need the anti-freeze for the corrosion protection.

JLew

Have you checked the radiator to see if it's plugged internally? Since you mention that this problem has slowly coming on.

Just a thought,

SP

how would i go about checking the radiator for blockage? i took a look at the coolant in the reservoir and the level is fine. no excess pressure released when i removed the cap and the coolant smelled normal when i took a real good sniff, not burnt at all.

i pulled the front apart again yesterday and hosed the hell out of it with water and a lot of crap came out. couple weeks ago when i pulled it apart, i just used compressed air and had a fair amount of stuff come out but i think the water worked better.

im going to have em take a look at it at work this week (i work at a vw dealer that is also chevrolet) and will do a coolant flush myself and re-fill with a 50/50 mix. will also do a trans service and fill with transynd before the next glamis trip in august

what is a normal IAT temp to see just cruisin down the freeway at 70mph with outside temp at 80*? i was seeing 100* on flat ground and 110-115* on some small hills. i didnt even think to look at what the IAT was when the truck was running so hot pulling the trailer, oh well

Do these trucks need to be "burped" of any air pockets that may be in the cooling system?

My IAT's were similar, but even worse, than yours. I then installed a DIY cold air intake (piping air from the bumper into the factory air box) and then isolating any engine compartment air from entering the air box using foam insulation. I now have IAT temps of 1 degree over outside air when cruising. In stop-n-go traffic, it rises because I don't have the airflow necessary to cool down the air box and intake tube.

I think your generation of air box is much better than mine, the LLY, but I would take a hard look at anything you can do to isolate the intake air from the engine compartment. Especially if you are experiencing a lot of fan activity. The wash from the fan blades forces hot air right into the intake on my truck. Then the turbo has to work harder which dumps more heat into the CAC which dumps more heat into the radiator which means the fan comes on more and the cycle repeats.

I am the old truck LBZ version but I think flushing out the cooling system might help. My wife's 2002 GMC was getting hot despite an overflow tank that was working and nothing looked bad but when I used the Prestone back flush kit I got mud like no end to it and flushed it for 30 min. The 230* norm went to 185* and ended the problems. Is the fan shroud intact? Sounds like a stupid question but I have seen people take them out for radiator work and leave the shroud off and wonder why the temps go way up. Were the new stats good a brand like stant or cheaper store ones. Also the 50/50 mix is the right mix.

how would i go about checking the radiator for blockage? i took a look at the coolant in the reservoir and the level is fine. no excess pressure released when i removed the cap and the coolant smelled normal when i took a real good sniff, not burnt at all.

i pulled the front apart again yesterday and hosed the hell out of it with water and a lot of crap came out. couple weeks ago when i pulled it apart, i just used compressed air and had a fair amount of stuff come out but i think the water worked better.

im going to have em take a look at it at work this week (i work at a vw dealer that is also chevrolet) and will do a coolant flush myself and re-fill with a 50/50 mix. will also do a trans service and fill with transynd before the next glamis trip in august

what is a normal IAT temp to see just cruisin down the freeway at 70mph with outside temp at 80*? i was seeing 100* on flat ground and 110-115* on some small hills. i didnt even think to look at what the IAT was when the truck was running so hot pulling the trailer, oh well

When I am driving at highway speeds if I look at the temp on the rear view mirror and my IAT on my Edge there is usually a 18-20 degree difference. In stop n go traffic it is much greater but, I also have done the air box mod to mine

JLew

It's plugged radiator tubes. The coolant - especially Dexcool, will deposit a polymer on the tubes that slowly reduce flow. There is no way to clean this except by either replacing the radiator or having a radiator shop clean the core. I have 40 years of experience with this problem in gas and diesel engines. If you could see inside the radiator, which is impossible in the DuraMax, you'd see a reddish (with Dexcool, white with some others) buildup at the end of each tube. When coolant breaks down this occurs, be sure and have your coolant flushed and refilled every two or three years when towing. A coolant bypass filter helps keep things clean, change filter annually. www.sancarlosradiator.com/dex-cool.htm click on the Dexcool pictures link.

would the power loss be related to the excess heating??

Get back to 50% coolant / 50% water. That's the cheap thing to try and most likely your problem.

It's plugged radiator tubes. The coolant - especially Dexcool, will deposit a polymer on the tubes that slowly reduce flow. There is no way to clean this except by either replacing the radiator or having a radiator shop clean the core. I have 40 years of experience with this problem in gas and diesel engines. If you could see inside the radiator, which is impossible in the DuraMax, you'd see a reddish (with Dexcool, white with some others) buildup at the end of each tube. When coolant breaks down this occurs, be sure and have your coolant flushed and refilled every two or three years when towing. A coolant bypass filter helps keep things clean, change filter annually. www.sancarlosradiator.com/dex-cool.htm (http://www.sancarlosradiator.com/dex-cool.htm) click on the Dexcool pictures link.

I think your on to something!!...My truck has been heating up easier and faster also...almost exactly as elcamino....so I just barely got done taking a look at my coolant this morning with my mag light (5am here) and looked like something I leave in the toilet:mad:...69k miles and my coolant is trashed...Mine is getting flushed TODAY..If it still heats up I will remove the rad and clean it...this has got to be what the problem is...There are more and more posts on here about our trucks running hot when they never used to..I will report back with my findings.

AXLENUT-- So I see your running amsoil coolant...is it safe to switch straight over to the Amsoil from Dex-cool?

dexcool is not the problem, for the 100 freakin thousanth time.

If you want to run green because you think you know everything and have been working on engines for the past 150 years then fine, switch to green and stop complaining.

The duramax was designed from the start to be 100% compatible with dexcool (unlike the early Gen I/II small blocks which had SOME isolated cases of intake manifold gaskets), so there should not be any problems. My dads 2003 tahoe has 200k on the factory original coolant. As long as you dont have a bad head gasket, dont let the coolant run low, and ONLY TOP IT OFF WITH COOLANT THAT HAS THE GM DEX-COOL LOGO ON IT (not the shit that says "mix with any colored anti-freeze!!" on the bottle), dexcool will last a long time and not give any troubles in a duramax.

ben

Hey Ben come take a look at what mine looks like and I bet you would be flushing it out quick....when its brown soup THERES A PROBLEM WITH MY DEX...new dex will go in and will be serviced again when it starts to discolor.

If you know my dex is good...why did my truck start running hot slowly but surely when it never used to with the same loads? water pump is good, clean radiator on the outside, fan is working, temp gauge is working with Insight to back it, pan drained my alli 4-5 times and 7 spin ons in under 70k, clean fuel filter with PS in every tank, injectors are good, clean air filter and maf sensor, no codes period, etc.....All maintanence on my truck is done well before gm calls for it. The only thing to explain it that makes sense to me was posted above by axlenut.

so i gathered up my things to do a drain, flush and fill on the cooling system only to find out that my radiator is not equipped with the drain plug like the 01-early 06 trucks.....WTH? whats my best option now? if i were lucky enough to actually get the lower rad hose quick (that must be a joke or something) disconnect off the radiator, the mess it will make will be insane....

pull the clip out of the hose on the lower radiator and you can pull it off without making a mess, I pulled it off part of the way from under the truck then the rest from uptop.

how hard was yours stuck on? i work on vws for a living and all of our cars for the last 10+ years have used them and they suck large ones to get unstuck after theyve been on there awhile

dexcool is not the problem, for the 100 freakin thousanth time.

If you want to run green because you think you know everything and have been working on engines for the past 150 years then fine, switch to green and stop complaining.

The duramax was designed from the start to be 100% compatible with dexcool (unlike the early Gen I/II small blocks which had SOME isolated cases of intake manifold gaskets), so there should not be any problems. My dads 2003 tahoe has 200k on the factory original coolant. As long as you dont have a bad head gasket, dont let the coolant run low, and ONLY TOP IT OFF WITH COOLANT THAT HAS THE GM DEX-COOL LOGO ON IT (not the shit that says "mix with any colored anti-freeze!!" on the bottle), dexcool will last a long time and not give any troubles in a duramax.

ben

DexCool is crap when air gets entrained in the fluid. It's not worth the problems, flush it and switch to real heavy duty coolant and never worry again. Sorry - I don't buy the DexCool is okay-it isn't. But we can disagree.

I think your on to something!!...My truck has been heating up easier and faster also...almost exactly as elcamino....so I just barely got done taking a look at my coolant this morning with my mag light (5am here) and looked like something I leave in the toilet:mad:...69k miles and my coolant is trashed...Mine is getting flushed TODAY..If it still heats up I will remove the rad and clean it...this has got to be what the problem is...There are more and more posts on here about our trucks running hot when they never used to..I will report back with my findings.

AXLENUT-- So I see your running amsoil coolant...is it safe to switch straight over to the Amsoil from Dex-cool?

Yes it's safe to switch over to Amsoil coolant, but I had my system flushed by a commercial radiator shop first. They flushed it three times to get all the Dexcool out of it, then refilled with Amsoil. It's a bit more money, but lasts a long time. DexCool isn't the only coolant that will produce radiator problems, any of them will result in problems if they are allowed to go too long. Amsoil test strips are available, but most shops or oil analysis labs can run a coolant test to extend flush and fill cycles. We all worry about oil and completely ignore the cooling system - I'm as guilty as anyone.

Just be sure the coolant you choose meets the ASTM D-6210, ASTM D-3306, ASTM D4985-98, ASTM D 6210-98 specifications - especially the D-6210 for heavy duty engines. www.astm.org/Standards/D6210.htm Caterpillar and Cummins Filtration among others offer extended use OAT coolants, there are many products available.

When the engine temperature starts to climb higher over the same course, with no obvious signs of problems, i.e. low coolant level, leaking cores (including heater) leaking pump or slipping belts, bad cap, etc. then its usually plugged tubes. Never had a bad thermostat cause the problem. Quality of dilution water also can be a factor, if the water is high in minerals or particulates (turbidity, such as well water containing sand) the polymerization characteristics of the coolant can coagulate these into a solid flock as it deteriorates. That's why some recommend using distilled water to mix with the coolant. I hated it when it happened, but with the older brass/copper radiators it was time for a cleaning or recore, or with the new aluminum/plastic stuff, I'd just swap in a new one.

One more freak thing to consider is a collapsing radiator hose on the waterpump intake. After a huge amount of parts swaping, changing this hose solved the overheating problems on my brothers 7.4L gasser. The hose would only get soft when hot, which would of course occur when he was towing, so it was not an easy diagnosis.

how hard was yours stuck on? i work on vws for a living and all of our cars for the last 10+ years have used them and they suck large ones to get unstuck after theyve been on there awhile
Clip came out easy and it took a little bit of tugging to get the hose off but wasnt bad.

i ended up doing a coolant flush at work using our bg machine. was a bit tricky as i had to install it into the system quite a bit differently than how im used to with vws, but it worked out. the coolant was suprisingly dirty and very very orange meaning to me that it had too much coolant and not enough water. wont tow the trailer for another couple weeks so not sure if its helped. will definately be doing a transynd service on the allison before i tow then too, its quite a bit overdue

i ended up doing a coolant flush at work using our bg machine. was a bit tricky as i had to install it into the system quite a bit differently than how im used to with vws, but it worked out. the coolant was suprisingly dirty and very very orange meaning to me that it had too much coolant and not enough water. wont tow the trailer for another couple weeks so not sure if its helped. will definately be doing a transynd service on the allison before i tow then too, its quite a bit overdue

Keep us posted. I'm betting you found the issue.

i did a simple drain and fill on the allison this weekend with transynd. wowzers, it shifts so much better and the temps around town seem a little cooler as well. im going to be towing the trailer this weekend so we will see how it goes.

and since it has just over 75K miles, it was due for an oil and filter change as well as an air filter replacement. odd thing is the new filter from GM is no longer a donaldson unit, but rather an ac delco part made by mann filter....hmm

I did that BG machine flush and fill with Extended bulk green product at Coop he put the BG conditioner in it also. With the BG flush product it cleaned up my system in one push and some tail water that was clean enough to just go green. My truck has 32k mi. opposed to your mileage of 75k that needed 3 flushes so I see the dexcool sticking alot more from just that much more mileage. I haven't experienced any bleed-in of red from the change over with 1500 miles so far and hot summer running I think it's good. Point I guess is glad I changed our diesels over. Good thread on several topics....

Fan Clutch Diagnosis

Document ID:774320

1. Ensure the engine coolant level is full.
2. Ensure the colling fan drive belttension is correct and not slipping.
3. Position and secure a thermometer between the fan clutch and the radiator.
4. Ensure the cooling fan is disengaged before starting this test.
5. Sufficiently cover the radiator grille to restrict the air flow.

Important: Do not allow engine temperature to
Exceed 121 degrees C (250 Degrees F)
6. Start the engine.
7.Turn A/C on.
8. Operate the engine at approximately 2,000 RPM.
9. Inspect the thermometer when the fan clutch engages.
10. Do not continue this test if the fan clutch does not engage between
85-96 degrees C (185-205 degrees F).



Fan clutch engagement will be indicated by an increase in fan air noise, fan
speed, and a drop of about 3-10 degrees C (5-15 degrees F) on the thermometer reading.

If the clutch fails the test Replace it.


My 2007 truck is runing hotter the it used to so I am going to do this test.
Wayne

?? if the fan came on at the temps indicated, it would be engaged at all times. that doesnt seem right?

The temperature is the air temp between the radiator and the fan clutch.
Not the engine coolant temperature.

Wayne.

oh snap, i didnt think about that, sorry. i may have to give this test a try if im still having issues this weekend

only marginal improvements noticed this weekend. it still heating way to fast on acceleration and the power just doesnt seem to be there when the digital temp gauge shows over 220*

something still isnt right :(

Did you test the operating temperature of the fan clutch?

Wayne.

have not been able to yet, hope to give it a whirl soon

is it possible this might be a result of the rubber fuel lines starting to collapse under suction? i havent gotten a P0087 code yet, but its symtoms seem to be on par with those having those problems. the truck seems to also be using more fuel than it used to before, both towing and unloaded. injector balance rates are well within specs as per the tech 2

i just replaced the cooling fan assembly on a customers 06' lbz[last august],,it just kept getting hot [220deg] when towing,after it wouldn't got 200deg pulling 14,000 lbs,,also took out a ton of bird feathers on the front of rad /between intercooler and rad