It has been suggested we create yet another OH thread to focus on a creative effort. As the title suggests, this thread is to move forward in:

1. identifying the sources of overheats in our trucks, mainly LLY's, but not excluding LB7's, due to inherrent design weakness.
2. implementing solutions based on above.

This will become more clear as the thread develops.

Please do not post here unless:

1.) You have an interest in solving this problem
2.) You believe there is a solution(s)
3.) You don't have a personality problem that prevents you from adding to a collective, productive effort.
4.) Want to keep your truck and maximize its utility in severe environments

This is not a political thread, there are other threads to voice your feelings on GM's policies. That is a debate that is not welcome here. Let's begin with what we have learned so far from the Overheat thread in the last month. The next few threads may be transcribed from that source.

I don't think we all paid $40,000-$50,000 to have to be engineers here. However, maybe installing some kind of electric fan(s) could help. Is there room? Dunno. Will it mess with our warranty? Dunno. If GM says there is no problem that they know of; how can we come up with our own solution without some potential reprocussions?
Your idea is surely in the best interest of the problem at hand but it may turn out to be a recipe for dissaster to a lot of people who may find themselves kicked out of their spendy warranties. I don't agree with GM's current status to sit on their hands but our only recourse is to play by their rules. If they don't want to play, legal is the only way to force their hand. That way no one loses for time to come.

shawnrans - RIGHT ON!!!!!
You nailed it, it aint our problem, when you pay 50K for a rig, you want it to work as advertised. Nowhere in the brocure I have sitting on my desk does it say DO NOT DRIVE IN THE DESERT SOUTHWEST ( where I live and the temps today call for 120+all week.
Simple - GM has to make it right or buy it back!

Thank you for the new thread. I was going to start one myself rather than dig thru 100+ pages etc. I've stayed out of this because my runs cool, but now have seen excessive ECT when towing myself. Mine maxed at 225° according to the Attitude. EGT's were manageable at 1400°f or less in most cases and this was 10k+ across MN, ND, and MT including the Cont divide, Bozeman Pass et al. Ambient temps in the 90's and speeds were at or above posted limits most of the time. I was never in fear of a meltdown, but it sure would have been nice to have coolant temps lower. For the record, I was running more than stock boost levels which Edge does NOT alter. This goes in part to the IAT/ intercooler heat load theory.

I have some thoughts and have started digging into my old contacts. I've been through this with the 6.5 before and am hopeful that the engineer that I dealt with has not yet retired.

If someone can put together a brief outline of what has been tried, an possibly email it to me to save from extending this thread, that would be appreciated.

So far I have been told that the blade, clutch, t-stats, and water pump listings are same for 2001-2005. Not sure if there were any supercessions made or not.

On edit: Guys, please respect killerbee's wishes and refrain from posting gripes etc in this thread...

First the problem must be isolated. You need an LB7 or LLY that does not overheat when towing heavy in the summer. Measure the water temp going into the radiator, and coming out of the radiator. Now an LLY that gets hot, and measure the temps.

Is the radiator dropping the same temps in both trucks? Is the engine producing more heat in one truck than another?

Essentially, we need to find the differences between two trucks, one with the problem, and one without.

McRat is correct - to fix the problem, first one must define it. Overheating is not sufficient. I have an LB7, that usually won't get hot. Once in a while, while climbing from Winslow to Flagstaff at or above max GVW, it will get hot. It happens after running for some miles WOT, and with EGT around 1250. The fan will be running, and gradually the temp guage will go to about 220 - 230. It seems that at that point, the 2nd thermostat opens all the way, as the temp will drop back below 210 in a big hurry. And no, I didn't get out of the power. I appreciate that for most of you, this in not overheating. However, perhaps there is something in the information stored in my feeble brain that might be useful to this group - in any case, I am willing to help all I can, as I haul heavy, haul all over the desert southwest, and haul in the mountains.

Some considerations to measurements and conclusions:

- pressure is always temp related (pv=mRT); in front of the stack temp is lower that behind, therefore pressure drop depends on a lot of other factors
- the fan slips more with high temp because the silicone looses viscosity - but the waterpump speed increase with engine speed...
- the fan does not speed up linear with engine speed, the slipping is bigger with higher rpm than with lower
- there is an influence in airflow versus speed over the stack, Fingers measured 0.25 iw with engine off at 50 mph (no engine driven fan) - I assume more with higher speed

Solution of the problem?
- different fan with higher pitched blades (more noisy)
- engage fan earlier (waste of fuel, loss of power, noise)
- electric fans will not flow enough air (5500 cfm is the biggest avaible from flex-a-like but thats not enough...
- better intake (snorkel for the people in desert climate like Arizona, New Mexico...like Australia (Safari Snorkel) to get cooler air with less dust...
- bigger cooler (wider?)
- bigger IC like Banks
- air dam (fingers...) to improve air flow and pressure
- less back pressure (cat, exhaust)

There is NO simple solution - GM could just reduce boost when driving on altitude via a Firmware flash and change the fluid clutch to engage the fan much earlier - would be a cheap fix for them but not a nice one for us....

:confused:

Much has been looked into. I came into this topic on post 1272 here (http://www.dieselplace.com/forum/showthread.php?t=14625&page=32&highlight=killerbee). Anyone who would like to see the developments, read everything that talks about IAT air box temps, and pressure drop across the stack. That is where the biggest gains have been had. RickDLance conducted monitored cross country towing trips, and we disected the data, which was VERY revealing. At one point running hot, his IAT topped at 221 degrees! That's before turbo compression heating it to over 500 degrees. One of us will list some of the findings.

Fingers has been involved in this also. What we found is that the pressure drop across the stack remains constant with speed, at a very tiny value. Again go back and read if you are interested, this thread picks up where we left off. I am waiting for my Magnehelic gauge before I can further dissect the pressure gradients on the front end and undercarriage.

Someone will post a reading list here soon.

The conclusions drawn so far are staggering. And with very little innovation, Fingers air dam doubled stack cooling flow at speed. No kidding. That is just the tip. I hope he arrives soon and will continue to develop his trials here.

For the isolated one or 2 of you who don't know how to read the first post, thanks for applying. We'll be in contact.

I think I meet your requirements killerbee.
There has to be a solution!

I have tried the cold air intake from the bottom tube of a Volant air box as well as leaving the hood uplatched during a tow. I know others have removed the entire grill or a headlight. All with no help.

Good job KB!

I personally think a fan solution by itself is just a bandaid, but if it's part of a package of other improvements, I'd take it. A couple of things I've pointed out are differences between the GM and Ford air flow control and stack design. Specifically:

Grill and shrouding that can focus air into the stack and increase velocity into stack.

wider separation of stack components (which will allow more free air flow).

Possible relocation of trans cooler into it's own air stream.

And just on the trans side: possible heat shield or insulation on cooler return line to trans where it runs an inch or two from the exhaust pipe. Certainly a radiant heat gain especially at lower speeds.

I know this may sound kind of "ghetto", but if there's insufficient flow throught the stack, has anyone tried removing their hood and seen that effect on temps??? While it's certainly not a permanent solution, if underhood temps or pressures are keeping flow down through the stack, then perhaps louvering or strategically placing a couple NACA ducts in the hood could solve some airflow problems??

Just an idea . . .

I don't care who your that's funny....

i have tried that and it works . i have also cut the roof of my cab off so i can keep cool just like my engine .

Well I don't know about making a convertable d-max, but if yanking the hood works, why not look for a spare hood in a salvage yard and try either stamping a few louvers in it, or putting some wickers in front of a flush-mounted duct to generate some low pressure and draw some hot air out??? Not the most glamorous solution, but if it works . . .

Quick review:

I have been measuring the differential pressure across the stack as a means of quantifying the amount of air flow across the stack. All my measurements have been in the same probe locations using a Kuhlman guage. Units are inches of water. I can measure other differntial pressures, but have been focusing here for right now.

In short, I have found that the unengaged fan still draws between .25 and .75 inches depending on RPM, maxing out around 1500 RPM at .75 inches. I have not had the chance to check when the fan is engaged, yet. I had one brief period when the fan was drawing more, but I think the clutch was cold and partially engaged.

Stock:
At speed, I never saw above what the fan was drawing (.75) regardless of speed. I even shut the engine off and the max I measured was .25 at 50 and 60 MPH. I didn't try 70 :)

My conclusion is that there is essentially no draw from speed.

Ghetto Air dam:
I have blocked the area between the frame rails from the bottom of the Radiator bulkhead to the bottom of the frame. Below that I have installed a removeable air dam.
http://dieselplace.com/forum/attachment.php?attachmentid=6426&d=1121439062

It is not as wide as I would have liked, but the material was limited.

Measurement showed little differential over fan draw below 35-40.

MPH | w/Ghetto Dam | w/o Ghetto Dam

25 MPH | .75 | .5 - .75 *
35 | .85 | .5 - .75 *
50 | 1.0 | .5 -.75 *
60 | 1.25 | .5 - .75 *
70 | 1.5 | .5 - .75 *
note * ( w/o varied with Revs, with did not)

I extended the dam closer to the ground today and did a run but the extension didn't hold up at 75 MPH and I had to abort. Inial reading showed even greated differential across the stack.

I will be mapping the hood for pressure drop zones later this week, that is on the menu.

Once we determine just what static pressure of the stack front is, as well as the underhood area, and compare that against alternative low pressure areas (like the hood) we can make calculated mods. I'm not much of a 'lawn dart' solver, and the hood is on the list.

Just as an aside for you few to try, one change that is simple that has apparently created an improvement was the removal of the plastic splash guard under and behind the bumper. Leads me to think, that it may be helping raise the pressure under the truck, an "air plow" of sorts. Cold air has proven it's worth the effort you put into it. Some of us are putting the gasser/old LB7 airbox that seals up to the fender openings. A simple mod brought down IAT's by 70 degrees (at 250 ECT), a significant power recovery.

We are not worried about ghetto here, if it works, we figure out why, and impliment a test in a proposed mod.

The first rule of air movement here is:

Air will, without exception, move from an area of hi-static pressure to an area of low static pressure, in a straight line. As simple as that.

The main problem appears to be that the pressure on the front of the stack, vs the back of the stack, is almost the same, even at 70 mph. Whatever will increase the front, or decrease the back, (or both) will increase cooling flow.

Diesel man, were you serious? What did you do and what were your observations?

Oh, one other thing. Fingers you reminded me with the pic. Anyone who hasn't done it already, please add either GMC or CHEVY to your signature. The front ends being different may pan out to be significant as we assess the flow characteristics of each.

Just an FYI, expect actual volumetric flow (ACFM, if you like) to vary with the square root of delta P.

e.g., double the deltaP, and get 44% more ACFM.

FYI2, the dynamic head of 100F air at 70 MPH is 2.17 inH2O.

Just an FYI, expect actual volumetric flow (ACFM, if you like) to vary with the square root of delta P.

e.g., double the deltaP, and get 44% more ACFM.

FYI2, the dynamic head of 100F air at 70 MPH is 2.17 inH2O.

I hope you are here to stay!

I have been reading all the posts on this website for awhile. I have a 2004 1/2 lly duramax in a 4x4 crew cab dually, with a six inch lift and all the goodies. I am not going to tell you any details on this info, where I got it ect. Just trying to help. Just try what I am telling you and if this fixes the problem, you have a air flow concern, that may be due to the design of the veh. I have heard of 2 ways to do this, I have tried both with good results.1.. remove the headlamps, it takes 5 min, then drive it, or while pulling, pull over pop them out and keep going, see if that helps it should run cooler. 2.. remove lower spoiler, the one below the bumper, see if that helps.
I have a 10,000 pound trailer, I took a trip that made me travel over the grape vine, not sure of the climb but you people that are local maybe can help me out on the grade, but it's a long haul uphill. The truck got hot, 260 I backed out of the throttle to 35mph and it cooled down. I then did my homework and conducted the test I told you about above, they both worked no problems. I know this is not going to be a acceptable soulution for some of you, but I love my truck and I like G.M products so I will make mine work. I am going to switch out the grille and the hood to a 05 model that will fix the problem, but before I do so, I am going to try a little trick that was so important to the camaro's of the 80's.They too had a problem with air flow so a straight blade style spoiler was put on from the factory that would catch the air that flows under the veh and directs it up into the rad. You can't see it, it looks so simple that alot of people would leave it off or not replace it when damaged,then the veh would overheat, the design was very effective. I am going to try that and see if it works,which I am sure it will and the hood and grille may not be necc. I'll let you know, how it goes. I know it is disappointing when something is not right with your truck, I did not like it when I had to slow down. But it seems every truck out there has one fault or another right?. If I can fix it so I can do 75 up the grape vine I will, because if I do 40 it will be fine.That's better than put tranny's in every 50,000 like some other trucks I know.

I told the GM lady today that we have been working on the problem and have made some headway, that we are a very resourceful and determined group. Although I want them to fix the problem, I also support forging ahead with whatever we can find as well.

Although the issue has not been solved since last year, mainly because winter came and efforts slowed to a crawl, we have learned a LOT and continue to do so.

Keep pouring in the ideas fellas, the more shots taken the more likely to score a direct hit, and if not a direct hit then at least enough indirect hits to still win the game.

.

The stack is blocked off on the bottom by a permanent metal plate, it is a good idea to direct air to the radiator but implementing it may not be feasible.

The headlight thing was around last year, it is an effort to lower intake air temps. Its also a decent idea, but not so workable as far as the law is concerned.

.

KILLERBEE - IT WAS JUST A JOKE . I AM HOWEVER WATCHING THESE THREADS VERY CLOSLY . I MUST BE ONE OF THE LUCKY ONES . I HAVE NEVER OVERHEATED OR EVEN COME CLOSE TO IT. whoops sorry for the caps . i have 38.5 inch tires and a 11 inch lift , so maybe i get better air flow ????i tow regularly through havasu arizona . outside temps have been between 110 - 118 . towing about 8000 pounds " 28 ft nordic power boat " . also towing my 28 foot toy hauler with my jeep inside from san diego to glamis through the mountains on the 8 freeway = no problems thats at about 11000 pounds . who knows

I'm no engineer but looking at all the cooling stuff the air has to pass thru before it gets to the radiator is a bit much. Maybe trying to cool too much and not having a big enough front end to allow sufficient air thru. Amazing to me it can do what it does in keeping things from melt-down.

It does look like a tough path but this stack design is proven over time on many many vehicles. It isn't new and has worked before, it is just being overloaded or perhaps flow hampered by the current design.

Still guys, the flow thing is great but don't forget the trucks that don't overheat nor the LB7 trucks with the exact same bodywork grill and stack (04 to 04.5) that have no problems. Why is the stack flow good enough for them but not the rest?

.

has anyone measured the square inch of thier grill opening and compared it with ford or dodge grill

if i remember that was one reason that dodge said they made the horseshoe grill bigger in the 03 trucks so that it would bring in more air for the higher hp and tq on the new engines

just a thought that maybe the grill is not letting in enough air

Is the radiator in the LLY the same as the LB7? If not, has anyone done a flow test of the cooling system to determine flow rate, cooling capacity and rate of cool-down? I'm not talking about Fingers air-flow tests.. BTW, those sure were extensive...

If it is the same, could the head redesign for the LLY's be the culprit? Sure, easy-to-change injectors are nice, but at what cost? Maybe water passages not run right, or a blockage at the headgaskets?

Do we have any radiator-shop guys willing to try to build an aluminum, racing-style crossflow radiator that could flow more?

Also, has anyone determined if the overheat is coming from a specific area of the engine, or is it a "general" overheat condition? The reason i ask is, I used to have a 455 Olds that would overheat and the problem always seemed to come from the rear of the engine. The problem turned out to be the aluminum aftermarket intake, it had no rear crossfeed like the stock one did. I had to tap the manifold to accept hose nipples, so I could run a hose to connect both heads. The overheat condition disappeared.

Just throwing out ideas...

Tom

After all of this round de round and all we have looked at I think the heat source is either bad castings in the turbo housing or more likely the cylinder heads themselves. Ricks inlet/outlet data, although not precise, has really moved the burden of proof of the load off of the stack and into the engine.

Couple that with Ricks truck that did not exhibit the overheating problem until it blew up and had the turbo and heads replaced only to then have the overheating problem and the coincidence is too much to overlook.

I don't know how any of us could go about measuring temps throughout the cylinder head on a running engine. GM is capable of that task, taking an overheat truck and placing temp probes throughout the cylinder head and finding the heat source or sources.

Anyone have any ideas how to survey the temps around and through the heads?

Seems the turbo would be easier yet still difficult for us to map thermally.

.

Quick review:

I have been measuring the differential pressure across the stack as a means of quantifying the amount of air flow across the stack. All my measurements have been in the same probe locations using a Kuhlman guage. Units are inches of water. I can measure other differntial pressures, but have been focusing here for right now.

In short, I have found that the unengaged fan still draws between .25 and .75 inches depending on RPM, maxing out around 1500 RPM at .75 inches. I have not had the chance to check when the fan is engaged, yet. I had one brief period when the fan was drawing more, but I think the clutch was cold and partially engaged.

Stock:
At speed, I never saw above what the fan was drawing (.75) regardless of speed. I even shut the engine off and the max I measured was .25 at 50 and 60 MPH. I didn't try 70 :)

My conclusion is that there is essentially no draw from speed.

Ghetto Air dam:
I have blocked the area between the frame rails from the bottom of the Radiator bulkhead to the bottom of the frame. Below that I have installed a removeable air dam.
http://dieselplace.com/forum/attachment.php?attachmentid=6426&d=1121439062

It is not as wide as I would have liked, but the material was limited.

Measurement showed little differential over fan draw below 35-40.

MPH | w/Ghetto Dam | w/o Ghetto Dam

25 MPH | .75 | .5 - .75 *
35 | .85 | .5 - .75 *
50 | 1.0 | .5 -.75 *
60 | 1.25 | .5 - .75 *
70 | 1.5 | .5 - .75 *
note * ( w/o varied with Revs, with did not)

I extended the dam closer to the ground today and did a run but the extension didn't hold up at 75 MPH and I had to abort. Inial reading showed even greated differential across the stack.

Fingers, my truck does NOT behave the same way like your measurements suggest. I have tested that many times:

Driving in 5th gear approx. 1650 rpm and 55 mph engages the fan clutch many times but driving the same street same outside temp same gear but 65 mph and 1950 rpm and the fan almost never gets locked by the fluid coupling - either more air is flowing through the stack because driving faster and the higher wind pressure pushes more air or the fan pulls more air through the stack because it is rotating faster...

Compared to your truck mine sits little lower and is a 2005 GMC. Maybe GM changed the fan blade pitch or something else for 2005 or a GMC flows air little different - I assume the older Silverado like yours is worst thats why GM changed the Hood design on it but not on the GMC....just a thought

Today was the first day driving the truck after sealing off the front end. While ghetto I did a pretty good job of stuffing any holes where air could get around/under the stack. Only thing I don't have is an air dam. ;) Fingers, there are numerous openings in front of the stack where that cheap POS air deflector is located. One large opening where the tranny lines come through, and a couple towards the front of the flap. I sealed all those holes off and raised that flap so that air travels right through the holes in the bumper into the stack. :D

At 70mph the engine runs normal temps of 198*, the Ally appears to like the additional air and dropped about 20* to 160* max. Of particular interest was how fast the coolant temperatures dropped when coasting to a stop, I mean fast! From 70mph on the interstate to full stop on the off-ramp in less than a quarter mile ECT's dropped 6*-8* to 190*-192*. Considering there is still a lot of heat/btu's being shed by the block after running hard at 95* OAT that is pretty impressive IMHO. My ECT's have never dropped that fast. Also, EGT's dropped faster to. Appears the IC is shedding heat better to. That is until I slowed down! :o:

Driving at speeds under 30mph didn't seem to have the same result. Engine temps didn't drop near as rapidly, Ally wanted to run hotter as well. Appears the stack wasn't getting enough air through it at lower speeds: too high of pressure behind the stack most likely. This is why I suggested to plug those holes around the stack so we can see what affect is has on the P's along with the ghetto dam.

I'm holding off on taking the plugs out from behind the head lights and around the IC until we see the results of a ghetto dam coupled with a sealed front end. Hope this helps. JJ :)

mahalkita

Do you have any way to measure the pressure differential across the Stack? I would like to know what it is.

I will have to look into the fan clutch some more. Some one else can chime in here that knows how it functions. I seem to recall that the clutch is not simply an on/off clutch and can have partial coupling. If so, that could explain it. But I don't really know without checking your truck.

Time for a little research I guess.

I ran a computational fluid-dynamic simulation of the truck in a synthetic wind-tunnel. The truck solid model is clunky, but I'm a bit new with Solidworks, though old hat with CFD. Anyone who's better with Solidworks, and wants to model the truck in more detail, can send me the .sld* files for Solidworks 2005. No the mesh isn't super-fine, but a 28000 degree-of-freedom differential equation is about all my little Athlon can handle.

The model was run for 70 MPH at 1 atm and 68F. It's not a thermal sim...just CFD. It gives an idea of how the air distributes, and where the pressure zones are. No, I did not make it hollow to model air through the engine bay.

The first pic is just the model in the synthetic wind-tunnel.

The second pic shows the surfaces colored by local static pressure.

The third pic shows the underside pressures.

The fourth pic shows the streamlines that interact with the topside surfaces...lines are colored by pressure.

A few learnings...

The stagnation zone on the front is fairly low on the front face. That explains the bumper inlets, and why they raised the hood "forehead"...to raise the stagnation zone (highest pressure) higher toward the radiator.

The other "wow" are the low pressure zones on the fenders, created as the air bends around the headlight area. This will tend to draw air through any leaks near there from the engine bay to the outside. And, one is right where the airbox is....the worst place on the whole truck.

The last pic (different pressure scale), is for you guys looking at hood vents. There's where to put it..just forward of halfway, and you have about 0.05 psi differential to deal with.

Next I'll add a "ghetto dam" and see how things change.

cit1991/ Nice calcs- More than my comp can do but very interesting. That would point to sealing the stack and the spoiler even more I think. Look forward to your next run.

First let me say "wow"!
We are going to have some fun.

Mahakita,

For your example of speed induced cooling there are equal numbers of folks that don't benefit from it. The LLY appears to be so close to thermal instability, that very small differences appear to be significant, perhaps even something like your torsion bar settings. Suffice to say, a fan at 55 (empty) can't be mistaken as anything but poor inherrent flow.

Mine behaves much like yours. One guy said at 75 (empty), his fan clicks on more than at 65. That looks to be indicative of zero speed induced cooling.

cit1991,

I will be following up with a static hood map, but isn't .05 really not enough for hood venting?

The magnehelic arrived today, new toy. Unfortunately, I'm swamped till friday

oh, psi.

disregard. That's about -1 iw?

If the underhood P is over 1 iw positive, that's 2" delta. Again to be validated with the magnehelic

BTW, these things only cost about $25 on ebay, a hoot.

Probably too much to ask, but can you show the streamlines for the underside surfaces? I expect a compression zone at the lower front of the bumper.

One other feature of note is the crossmember between the front wheels is about 4"-6" lower than the bottom of the front bumper. I know, I know, draw it yourself. Wish I had a copy of solidworks to help out.

Forgive me CIT. I almost forgot. Good work.

Fingers, just a quickie. Any thoughts on how a large air dam affects mpg?

The lly with heating troubles really makes me wonder if the heat is coming from the new designed variable rate turbo. The Lb7 did not use a egr system and coolant to flow thru a portion of the turbo to cool it down. The LLY has a direct coolant line in which flows thru the turbo, this being known The turbo gets very very warm and the cooling system can only do so much 200 degrees of coolant temp trying to compensate for 1200 degrees egt? I am just thinking out loud with no real facts here, but something needs to be done in order to keep these trucks running good and cool.

Fingers, just a quickie. Any thoughts on how a large air dam affects mpg?

Good question. I don't know for sure, but all the other high MPG cars have em. So it can't be all bad.

The lly with heating troubles really makes me wonder if the heat is coming from the new designed variable rate turbo. The Lb7 did not use a egr system and coolant to flow thru a portion of the turbo to cool it down. The LLY has a direct coolant line in which flows thru the turbo, this being known The turbo gets very very warm and the cooling system can only do so much 200 degrees of coolant temp trying to compensate for 1200 degrees egt? I am just thinking out loud with no real facts here, but something needs to be done in order to keep these trucks running good and cool.

LB7s had a cooled turbo center section too.

I called the dealer today about my overheating problem. The dealer called me back and said Gmac is working on the fix and knows there is a problem. He informed me that they have no fix at this time. I will calling tomorrow to set up an appointment beause they need some info off of my truck . I can't beleive I have a truck that I can only look at!!!!

I have been reading all the posts on this website for awhile. I have a 2004 1/2 lly duramax in a 4x4 crew cab dually, with a six inch lift and all the goodies. I am not going to tell you any details on this info, where I got it ect. Just trying to help. Just try what I am telling you and if this fixes the problem, you have a air flow concern, that may be due to the design of the veh. I have heard of 2 ways to do this, I have tried both with good results.1.. remove the headlamps, it takes 5 min, then drive it, or while pulling, pull over pop them out and keep going, see if that helps it should run cooler. 2.. remove lower spoiler, the one below the bumper, see if that helps.
I have a 10,000 pound trailer, I took a trip that made me travel over the grape vine, not sure of the climb but you people that are local maybe can help me out on the grade, but it's a long haul uphill. The truck got hot, 260 I backed out of the throttle to 35mph and it cooled down. I then did my homework and conducted the test I told you about above, they both worked no problems. I know this is not going to be a acceptable soulution for some of you, but I love my truck and I like G.M products so I will make mine work. I am going to switch out the grille and the hood to a 05 model that will fix the problem, but before I do so, I am going to try a little trick that was so important to the camaro's of the 80's.They too had a problem with air flow so a straight blade style spoiler was put on from the factory that would catch the air that flows under the veh and directs it up into the rad. You can't see it, it looks so simple that alot of people would leave it off or not replace it when damaged,then the veh would overheat, the design was very effective. I am going to try that and see if it works,which I am sure it will and the hood and grille may not be necc. I'll let you know, how it goes. I know it is disappointing when something is not right with your truck, I did not like it when I had to slow down. But it seems every truck out there has one fault or another right?. If I can fix it so I can do 75 up the grape vine I will, because if I do 40 it will be fine.That's better than put tranny's in every 50,000 like some other trucks I know.your new grill and hood will only cost you money it will not help one bit I know from trying it my self that was the final straw for me

"Fingers, just a quickie. Any thoughts on how a large air dam affects mpg?"

Race cars have air dams right down to the ground for better aerodynamics. All I keep thinking of is Mama JJ scraping it when she parks the truck over one of those concrete stops. lol

cit, that's some pretty fancy stuff there, YEP! JJ

Here's my take on the heat issue, lb7 vs lly, etc. To some it will come as Philosophy 101. But it is the reason I wanted a fresh thread and the only way to move forward.

It does appear that the LLY produces more heat, exactly where, why and how, are questions that plague us and continue to make us chase our tails like a troubled dog.

The source of the additional heat is probably resultant EPA mandates, that required the oem to turn up the heat on combustion and EGR. But the great thing is, if I am completely wrong, it doesn't matter, because I know for sure that the additional heat, whatever the source, must be disposed of in exactly the same way. In the front end.

So I leave the question behind, because it won't benefit me to know, if in the end, the best solution is better heat transfer off of heat exchangers.

Back to that. To put these pressure readings in terms that make sense to most. One inch of water (what the heck is that?). compare it to 14.7 psi or one atmosphere. 1 iw is .04 psi of pressure. "But that's nothing, how can that make a difference?" Well that's about 10 pounds per square foot. On a 10 square foot stack, that's 60 lbs. Put it this way, if you had 60 pounds of air hitting you (like in a hurricane) you would have a hard time standing.

And this is not like swapping out the oil pan for a bigger one. There's no pill to take for this (and that's why we are fixing this while the oem has failed). The solution has to be derived by exploiting flow weakness and site improvement area(s) (plural).

Now what we are saying is that, and this began as a postulation, was that "if I can cycle the fan, when empty, at highway speeds, then the fan must be providing the lions share, if not all, of the cooling flow".. That was it. In most vehicles you never hear a fan running at speed (granted the elec ones are quiet, but still). It is only when running around stop and go.

Fingers prelim data showed just that! Nada stack flow. Without the fan, I can't go the drug store.

I also believe, and postulate, that each vehicle is unique, with it's own flow nuances. Fingers Chevy shows us one that is in a neutral state, no speed induced flow. My GMC appears to have a slight bit of speed induced flow, I think I can kill the fan by speeding up a little, while another I have examined, does the opposite. But neither is acceptable, nor will perform the extreme conditions task. I'll get a half mile further up the road than Fingers will, that's all.

Now slap on a mod that provides a significant amount of flow, fan unassisted, and you may be doing the equivalent of doubling or better, the effectiveness of the fan.

I feel compelled to suggest this also. That fan is a nuisance, noone likes it, we know it dumps 15-25 HP on the street, reduces mpg etc. Our goal should be to enhance flow so that you minimize it's engagement. I have said all along, never should this thing spin up at 70 mph, if it does, something is wrong. When I hear that thing drown out all conversation, I'll know it's my "friend" as one post put it. But never again on a flat open road.

Long winded...wake up all.

KB I'm with you on that lets:grd: . If Gm cant get off its collective Censored , then I guess we as the owner will and then I'll call corp and tell'em to stick it where the sun don't shine. Sorry, end rant

KB, that's a lot of brain worken' for that early in the morning. High test coffee? lol

Great job of explaining that, even I understood it which should be the DP idiot test.

KB, please take a good look at the area just in front of the stack where that flimsy flap is. I taped that bad boy so that it is now parallel with the openings in the bumper (Chevy) and covered any holes around the stack. Those openings appear to provide an easy escape for air to avoid the stack and go down/under the vehicle. I'm having good results so far. Sure wish I had a damn dam! I'm calling some body shops. lol JJ

"welcome to your dam tour, I'm going to be your dam guide..."

Since none of us are volunteering to sit on the bumper at 70 mph, we will resort to measurements. Your statement shows you have digested the material. Correct, the vehicle (and I have no reason to think the older ones are different) appears to be just lacking in inherrent flow. Remember, it's the hi-drag loads complaining most of OH. FWIW, air drag increases with the velocity squared. The guy trying to go 70, with 20 mph headwind, has over 3x the drag of the guy pulling 50 mph, no wind. All of that has to be overcome with HP (heat). But if we have no better flow (cooling) at 90 (70+20) windspeed, that's like having 1/3 rd the cooling capacity. Like running with one leg.

And we haven't even approached a hill yet!!

Rick, in all his glory, God bless him, shows you can OH the truck on a straight, at 24K. All he needs is a headwind to do it. At 70 mph, a 20 mph HW increases HP requirement a whopping 65%. Slower is the only option, until you can get more heat exchange to occur in the stack, to displace heat of the extra HP.

The guy who has a slight speed induced flow (additional cooling flow with greater speed), is at a great advantage.

It is even plausible that some vehicles have a slight inherrent reverse flow. THAT, I believe is the difference between a truck that Overheats, and one that doesn't (plus all the obvious uncontrolled variables). I don't want anyone responding to this (PLEASE), it is controversial and admittedly very debateable. Just take this as a point we will prove or disprove. Again, let's not enter a debate, or bring up Joe vs Shmo. Doing that will make this thread different, productive. Let's leave it to measured observations, postulations, modeled predictions, and comparative analysis.

"Let's leave it to measured observations, postulations, modeled predictions, and comparative analysis."

Sorry about that. I edit my post accordingly. JJ

No,no JJ. That was not directed at you. I'm not saying not to post your observations!

Gosh, this isn't Russia (what we silo guys used to say in the cold war era)

Sorry I came off that way. Please don't edit your posts, that stuff is important. I just use big words to inflate my own ego.

Someone mentioned Magnehelic here. Not sure if there are different "ranges" for these gauges, but I do own one sized for use balancing gas to air flow on small boilers It looks about the size of the old security guard time clocks, maybe a bit smaller...

Just curious if anyone has TRIED dual electric fans?

I know the CFM isn't there, but they'd be on ALL THE TIME rather than via thermal activated viscous coupling. Add to that the HP you'd free up.

I'm just wondering, as everyone says NO, won't work for diesels, yet see no mention of anyone actually doing the swap. Just the gasser guys.

How about a moron approach at this - flushing out the 50/50 coolant and going 100% coolant. Then in the fall goback to 50/50?

First let me say "wow"!
We are going to have some fun.

Mahakita,

For your example of speed induced cooling there are equal numbers of folks that don't benefit from it. The LLY appears to be so close to thermal instability, that very small differences appear to be significant, perhaps even something like your torsion bar settings. Suffice to say, a fan at 55 (empty) can't be mistaken as anything but poor inherrent flow.

Mine behaves much like yours. One guy said at 75 (empty), his fan clicks on more than at 65. That looks to be indicative of zero speed induced cooling.....



I think thats one of the problems very small differences make a huge difference at the end because of the thermal instability. Driving another day with another temp not exactly the same road and get different results...
It was me also that hat the fan coming on more often with 75 than 65 but that was a different place (more ambient heat, higher altitude and a higher speed limit (I10) compared to a normal street full of potholes where the legal speed limit was 55...
Then I have wide wheels compared to others etc...very difficult to compare. But I think Silverados of the 2004 type are worst with termal instability than the currents GMCs - so maybe another poll from the overheaters who drives what would help?

Has anybody tried the Banks Intercooler to help with heat reduction? Banks claims there is a lot of heat reduction with their design - but what about more induced heat into the stack?

Old rule of thumb for engine energy balance...1/3 shaft work, 1/3 exhaust, 1/3 coolant loss. Ok, even if it's a rule of thumb, let's see how the loads compare, since thermal load (not temperature level), is what determines how hot the cooling air gets (along with the airflow).

AC:

say 3 tons at R=3 (lots of duty and not very efficient, a house is typically 4 to 5 tons, and the biggest 110V window unit is about 1 ton). ==> 4 tons of heat load, 1 ton=12000 BTU/hr, so a high estimate of condenser heat load would be 48000 BTU/hr

Intercooler:

Say, turbo inlet at 1 atm, and 200 F, boosted to 34.7 psia, adiabatic efficiency of 70%. Engine is at 3000 RPM, with a VE of 70%. Intercooler cools the charge air to 150F.

Compressor discharges at 460F, and takes 55.7 hp. Flow is iteratively calculated to provide the required ACFM after the intercooler, and is 77.7 lbmol/hr. The intercooler cools the airflow from 460 to 150, and this means losing 168800 BTU/hr.

Using the rule of thumb, the engine, making 310 hp, also needs 310 hp worth of cooling. The calc is a simple change of units (of power), and 310 hp is equivalent to 789303 BTU/hr (duty of the radiator).

Total thermal load is 1006103 BTU/hr. Even with a 200F inlet temperature to the turbo, the estimated heat load of the intercooler is less than 17% of the total.

Now lets say we want to remove that total load, with 110F air, by heating to 200F. How much do we need? 1473 lbmol/hr, or 11145 ft3/min at 110F, 1atm. I guess that's why electric fans won't cut it.

I'll leave it to you guys to argue whether changes in 17% of the heat load(vs 18, 19, or whatever) is enough to tip the scale or not.

How about a moron approach at this - flushing out the 50/50 coolant and going 100% coolant. Then in the fall goback to 50/50?

100% coolant will agravate the problem. Coolant has a lower specific heat than water (it carries away less heat). Adding a Water Wetter that reduces surface tension might help, but...

I haven't seen what the problem is! Is the motor MAKING more heat? Or is the cooling system REDUCING less heat? Until someone tests that, you might just be trying to feed the horse in the wrong end.

Engine went from 520lb/ft to 605lb/ft with no change in radiator capacity, correct?

Just a thought, If two owners are near each other, "one with the temp problem and one without" to see if there as any assembly/ visual differences in the two trucks. Maybe a deflector or air dam is installed different or incorrectly?

I guess I am lucky my 04.5 does not have a temp issue towing or not. My 5er is around 10K and I run at at 210 or just below consistently.

I personally have never had an overheating problem. Just a quick question. By the time the air reaches the radiator, how much heat has it picked up from the trans cooler, A/C Condencer, & Intercooler? Is the air still cooler than the radiator temp, or is it not able to cool because it is the same temp as the coolant?

CIT, thanks, I had promised to do that rough calc in the other thread and didn't get it done. I don't have an annometer to check air velocity across the stack. That would help a lot here. I have only been using differential pressures as an indication of improvement, if any, in flow.

McRat, it is a valid point and should be done. There is the possibility that the temp rise of the coolant from engine inlet to outlet is just too great to overcome. This would indicate a flow problem with the engine or pump.

There is no doubt the LLY generates more BTU's.

Seems to me I remember a number of owners complaining about poor A/C performance in the LB7's. Since the A/C exchanger is nearly the size of the radiator, and in front of the stack, it makes me wonder if there is a difference in the A/C systems of the LB7 vs. LLY that adversely affects the radiator.

I'm not 100% convinced the LLY makes more heat that the LB7, but obviously I have no data either way. We did not see a lot of LB7 guys who were running a Tow Tune and towing heavy report a cooling problem. Certainly a tuned LB7 engine running 300RWHP is going to be able to make more heat than a stock 250RWHP LLY engine. Even so, with 2 trucks that have the same combined weight going up the same grade will require the same HP to get the job done.

But that is just "theory" without knowing the water temp delta for both the engine and the radiator.

If the engine is making more heat (bigger temp delta), then EGR, turbo backpressure, injector timing, water pump flow are all possible candidates. If the radiator is not releasing as much heat, then airflow, radiator coating (inside and out), fan operation require more attention.

Tuning has shown to be of benefit, which SHOULD be contrary to calculations since more horsepower equals more heat to take care of, yet the engine runs cooler for the same load and conditions.

.

Being that I have an LLY and previously had an LB7 - it is pretty obvious to me that the thermostats in the LLY are "set" at higher temps. My old truck would run at 190 - the new truck runs at 210. The engine probably has to run hotter to meet emissions, and if this is the case, GM cannot employ thermostats with cooler "set points" to let it run cooler.

Question #1 : Can you run the LB7 thermostats in the LLY?

Question # 2 : Has anyone tried running LB7 thermostats in the LLY to see what affect it has on the "overheating issue"?

Here is a description of the LB7 thermostat operation from the service manual (I found this posted by a gm tech over on the lb7 forum)...

The 6.6L diesel engine requires two thermostats for correct coolant flow. The front thermostat is a dual purpose thermostat. The front thermostat controls the coolant flow to the bypass port and to the water outlet. The rear thermostat only controls the coolant flow to the water outlet.


When the coolant temperature is below the rated thermostat opening temperature, the front thermostat valve remains closed to the water outlet and is opened to the bypass port. The bottom portion of the thermostat is raised off of the bypass port while at the same time the top portion closes the coolant flow to the water outlet. The rear thermostat also is closed to the water outlet during engine warm-up. This prevents circulation of the coolant to the radiator and allows the engine to warm up quickly. 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). The thermostat also provides a restriction in the cooling system, even after the it has opened. This restriction creates a pressure difference which prevents cavitation at the water pump and forces coolant to circulate through the engine block.

After reading through this - I wondered whether the LLY thermostats allow greater flow and are allowing cavitation to occur at the water pump. Thoughts anyone?

- jeff

KB, all is well. Like Joe Friday used to say: Just the facts Mam! Best to keep things concise, to the point, and as factual as possible. My post didn't meet that criteria. Didn't want this thread to stray off center by setting a bad example.

McRat, unfortunately the answer may be yes and yes. Loved the horsee analogy!

cit1991, like WTF? Condensed English 3rd grade version please! lol JJ

I just got done reading this entire thread. Some interesting data so far. I have never overheated with my 2004.5 LLY. The only mods I have are a Juice/Attitude (on setting 3), both original versions (not the updated ones), an AFE drop in air filter, no kitty and a 4" Magnaflow. I am running stock suspension, but turned torsions and 285 tires.

I pull rather small loads on my truck, usually motorcycles and gear. The last load I had was 3 bikes, all the gear and such...so about 1200 punds of stuff. The ambient temps out at California City were about 106F and I had the A/C on full. 198F was normal out there, but if I hit small, but sustained grades I would get engine temps of about 204-205. Near my house in Brea, CA, in the summer at average temps of 85 to 90F I have engine temps of 192 empty, but if I pull small grades going to work with those ambient temps it will go up to 198. In the winter my empty temps are around 185-187F. All of the above were still at level 3 on the J/A, but I was going very easy on it, if at all. it seems my truck is a little more tolerant of temps and has yet to overheat even with a small load. I wonder what the difference is compared to trucks of the same year and config?

-delete-

Engine went from 520lb/ft to 605lb/ft with no change in radiator capacity, correct?

GM press releases for the new motor stated...

"Increased flow water pump and new thermostat settings".

Those who have checked the part number for the new water pump - find that the part number is the same '01 to '05. Which begs the question - is there a difference? Do they now supply the new water pump for all applications ('01 thru '05) or did they decide to save a few penneys and not supply it?

- jeff

I just got done reading this entire thread. Some interesting data so far. I have never overheated with my 2004.5 LLY. The only mods I have are a Juice/Attitude (on setting 3), both original versions (not the updated ones), an AFE drop in air filter, no kitty and a 4" Magnaflow. I am running stock suspension, but turned torsions and 285 tires.

I pull rather small loads on my truck, usually motorcycles and gear. The last load I had was 3 bikes, all the gear and such...so about 1200 punds of stuff. The ambient temps out at California City were about 106F and I had the A/C on full. 198F was normal out there, but if I hit small, but sustained grades I would get engine temps of about 204-205. Near my house in Brea, CA, in the summer at average temps of 85 to 90F I have engine temps of 192 empty, but if I pull small grades going to work with those ambient temps it will go up to 198. In the winter my empty temps are around 185-187F. All of the above were still at level 3 on the J/A, but I was going very easy on it, if at all. it seems my truck is a little more tolerant of temps and has yet to overheat even with a small load. I wonder what the difference is compared to trucks of the same year and config?

I dont' think you have a problem at all. Your temps are completely within a normal operating range. You are running cooler than I am when I am unloaded (and my ambient air temp is 80 degrees). I wouldn't worry about it.

- jeff

I think your truck will overheat with a real load, I tow way more than you and my temp doesn't move at ALL.

.

There are two thermostats that have different initial opening temperatures and "full open" temperatures. There is no reason to believe that his truck will overheat given his low temperatures.

If you try whipping things up and getting folks who don't have a problem to think they do - then you may end up wasting so much of GMs time, that they cannot effectively work on a solution. Just my 2 cents.

- jeff

I took the same route this week, same ambient temps 110 - 116 high mountain passes, one empty and the fan was on and loud, and I didn't get hot. Three days later ( same road, same ambient, etc,) with a camper on the back temps shot up at every climb.

If you try whipping things up and getting folks who don't have a problem to think they do - then you may end up wasting so much of GMs time, that they cannot effectively work on a solution. Just my 2 cents.

- jeff

Ok Jeff, your 2 cents are spent. I'm sorry that you don't seem to think that this is a real issue, and that those of us with problems are just nutballs that have caused our own issues my modifying our trucks, tow at insane speeds, with insane loads, and should just slow down on hills until were at an LLY happy speed of 25mph. :blahblah:

The whole purpose of this thread was to get on with solutions, as the other thread had become too large. Thermostats, pumps, radiators, cavitation, Jupiter aligned with Mars has been covered over there. Please read it before reposting the same stuff here.

:rant: over.

Sorry - you don't get to say when my two cents are spent. You guys don't own this board - it is an open forum.

Where I come from - it is okay to attack an idea or a statement - it is not okay to attack a person. I haven't attacked anybody - you just don't like what I have to say - that's your problem.

I actually spent several hours reading through the overheating thread looking for references to thermostats and it looked to me that it wasn't pursued. So back to my original questions (which shows I have some interest in solving the issue!)..

1. Do the LB7 thermostats fit in the LLY?
2. If yes, has anyone (who has an overheating issue) tried using the LB7 thermostats in the LLY?

Earlier this morning, I sent a PM to lancedmax asking if he had tried different thermostats on his '05 and offered to send him thermostats and gaskets if the lb7 stats will fit (on my dime).

- jeff

I, too, noticed my fan coming on at freeway speeds last week when I was headed to AZ through Barstow. I thought it was odd (even though the OAT was 109*) since I had the cruise set at about 87mph. I noticed the fan coming on a couple times on the return trip as well (OAT 120+ and unloaded). I never saw the trans or coolant temp gauges move at all and the Attitude recorded the highest coolant temp for the whole trip as 206*. The ONLY explanations I can come up with for this are:

1) Fan clutch is getting hot independantly of coolant temps (i.e. underhood temps) and engaging/disengaging "randomly"

2) High-speed airflow SUCKS through the stack and/or high-pressure is building up in the engine compartment restricting airflow.

I'm no MENSA or engineer, but it seems to me that airflow definitions and improvements should be pretty high on the priority list for solving this issue.

It's been a long time, but if I remember right the parts department at a local chevy dealer told me they are the same stats. Call a dealer and see. Better yet, go down there, the diagram of the engine is very revealing and clears up how the water flows thru the system.

.

Thanks Chris! That's what I wanted to know - I'll take a run down to the dealer this afternoon.

- jeff

Tx, let the pot simmer partner. There are some new players in this thread with some good math and hard data backing the discussion. No way to get around some rehash.

Jeff, take the politics elsewhere, please. And they are the sam stats LB7, LLY.

All, in the name of cutting out some of the fluff, reports of Stock trucks overheating or not are not needed. (sorry) What IS needed are reports of changes that you may have done that changed an overheating truck into a real puller or vise versa. No changes in overheating after a mod is good info too. Another interesting thing is something you want to try and need some technical advice or need to know if it has already been done.

And that is the last time I will even try dictating etiquette here. I promise.

This is my first time posting but I think I have some info that might help.

01 -06 all take the same thermostats according to my dealer. one is 185* and one is 180*.

This is my first time posting but I think I have some info that might help.

AND....... where'd ya go painterjoe? Don't play with our emotions! Spill the beans! lol JJ

CIT, I also have wanted to do that math. Thanks for posting it!

Now, I didn't double check your math, but assuming it's correct:

"Now lets say we want to remove that total load, with 110F air, by heating to 200F. How much do we need? 1473 lbmol/hr, or 11145 ft3/min at 110F, 1atm."

I measured my radiator area, 2'10" x 1'9" is 4.95833 square feet. So you would need 25.54 MPH of air flow (at 110*F) through the radiator to dissappate that much heat. Keeping in mind that this much heat is only generated at WOT at full rated engine output. The airflow required goes up as radiator efficiency drops (from age, dirt, ect)

This should NOT be a problem with the truck. HOWEVER, as Fingers has measured, there IS an airflow problem through the stack. So if we improve airflow through the stack (like with the "Fingers" air dam) the existing radiator has enough capacity. The key is to get air through the stack.

This may sound stupid, but given that the front T-stat is a bypass type, and that the bypass must close to get full cooling system function, is it possible that some engines were built with the wrong T-stat (the non bypass) in the front position?

For what it is worth a buddy of mine at work has an 05 2500HD with a 6.0 gas engine and it was overheating with his plow on. (He understands to keep it down has much as possible when driving around). Anyways he went back to the dealer and they told him there was a different clutch fan available and they installed it under warranty. That fixed his problem. Probably not the source of these problems but certainly a point of interest.

Tx, let the pot simmer partner. There are some new players in this thread with some good math and hard data backing the discussion. No way to get around some rehash.

Jeff, take the politics elsewhere, please. And they are the sam stats LB7, LLY.

All, in the name of cutting out some of the fluff, reports of Stock trucks overheating or not are not needed. (sorry) What IS needed are reports of changes that you may have done that changed an overheating truck into a real puller or vise versa. No changes in overheating after a mod is good info too. Another interesting thing is something you want to try and need some technical advice or need to know if it has already been done.

And that is the last time I will even try dictating etiquette here. I promise.

I agree. I know re-hash is inevitable and who knows something new could be noticed. I really shouldn't even have addressed the guy reporting about his truck towing the light loads, it wasn't anything to do with overcoming or identifying the problem, which is our direct focus here.

I would like ideas on quantifying bypass flow, it was something we were aware of before but unable to do and could potentially screw cooling flow to the radiator.

.

How many degrees does the cooler take from the ambient air...or maybe that can't be answered with just a straight number due to so many variables? Perhaps the core of the cooler is being heated by hot air that can't evacuate?

Sorry if this has been discussed...didn't see it.

On edit: I know it has been discussed, but what are critical temps for our trucks (LLY) as far as engine and tranny? I'm talking the absolute limit before they are considered in "overheat" status.

This may sound stupid, but given that the front T-stat is a bypass type, and that the bypass must close to get full cooling system function, is it possible that some engines were built with the wrong T-stat (the non bypass) in the front position?

Good idea, but we checked before and they are not swappable.

.

This is my first time posting but I think I have some info that might help.

AND....... where'd ya go painterjoe? Don't play with our emotions! Spill the beans! lol JJsorry about that,computer problems. anyways... About two weeks ago we went up to Idaho from So.Cal, towing right at 10,500lbs. with my new 05' LLY. I was experiencing the same overheating problems, moreso going through the Ca. and Nv. desert granted the ambient temps were higher. About 200mi. outside of Idaho falls the truck lost power and the check engine light came on. It would take forever to get up to speed but it would still pull the grades right at 55 and run the flats at 65-70.For the 200mi. or so into Idaho falls I watched the temp gauges like a hawk and they did not move one bit. When we got to our dest. I took it to the a dealer, they said the code was showing low boost pressure and there was a bulliten for loose turbo lines.They tightened up the lines and it was back to it's old self,Making tons of power and still getting hot. I don't know if this helps at all but I figured its worth a shot.

painterjoe, sounds like you had a legitimate failure of the turbo connections which set the CEL. The situation we're talking about is where coolant temps are uncontrollable and the truck truly overheats. Glad they fixed your problem though.

On edit, there may be some interesting intel in painterjoes post. He was able to creap up to 55 mph on grades and run 65-70mph on the flats without budging the ECT's. The lack of turbo boost and heat through the IC likely kept ECT's in check. Once they reconnected the turbo the truck is making tons of power and still getting hot.

Maybe the LLY in/of itself doesn't produce temps too high for the stack, the turbo may be the back-breaker. Sounds like his stack was flowing air through it, interesting? Is it possible for the IC to build up so much heat so as to create a "thermal wall" and restrict or slow cool air from passing through the stack? Where the heck did that question come from? lol

Edit #2: Thinking this through if the turbo wasn't working the LLY wasn't likely producing 310hp either, not as much heat either. This would explain the lower ECT's. Oh well! JJ

Does anyone have a truck that does NOT overheat and lives near Fingers where they can pull his ballbuster hill for data?

I would love to see radiator inlet/outlet temps between two trucks, one that displays the problem and one that does not.

.

I knew this was going to be fun!

You guys have done superb job of staying civil, great mind-melds happening.

New fresh perspectives. Rooster you need to get your post count up, don't be shy. BTW, the air that finally makes it to the rad is well over 130 usually. 150 at times from ricks data I recall.

thought for the day. Please resist telling how proud you are of your truck for pulling 8000 lbs on an 85 degree day. Chaff. We have just about seen every report known to this vehicle on the conditions that lead to running hot, so mostly there is nothing new in a overheat report placed here. Data is what we're after, numbers if possible. True you never know what a post might reveal or inspire, so I say it with a dash of salt.

Also, a lot of the technical aspects were covered a year ago, so a few of you could go over some of the OH thread,

HERE (http://www.dieselplace.com/forum/showthread.php?t=14625&page=6)

I know that sounds sleepy, but please get an education there, it is full of good stuff. Then come here if there is something that stands out to you. Just trying to cut down some of the repetition, especally the basic stuff.

This is grad school baby!

Cit

Loved the energy balance dude.

Materials are here to make air dam prototypes. The laser cutter is ready. I hope to have the first prototype made and installed by the end of the week.

I will be blocking from the bottom of the radiator bulkhead down to within 4" of the ground. Dam should go full length, fender to fender.

Then I will pull a load :)

I haven't towed anything heavy with my '05 dually yet, but that will be coming soon enough. I have been reading and learning about this problem, and was looking at the base of my hood near the windshield and it looks like there is a fair sized area that could be used as a cowl induction intake. The metal in that area of the hood would need to be opened up and a passage made for airflow, but it could possibly add more air, at least at speed. It looks like 04's hood is different, so it might not work on them. It's just an idea, might help might not.

This is a excellent topic lots of good information.

Edited for content by River&Sand

Opening the hood at the windshield base will create more high pressure under the hood, which you don't want. Even if it didn't, you would flood your heating/cooling ducts with hot air. You don't want either scenario.

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I will be doing a Cowl Induction intake on the White Truck in the next few months along with relocating the A/C exchanger and trans cooler. I will also turn the stock intercooler into a water/air intercooler. But this will not help anyone directly, as it's done for racing, and will not tow over 8000lb. I will post instructions as I get each one done.

Materials are here to make air dam prototypes. The laser cutter is ready. I hope to have the first prototype made and installed by the end of the week.

I will be blocking from the bottom of the radiator bulkhead down to within 4" of the ground. Dam should go full length, fender to fender.

Then I will pull a load :)

Fingers
Within 4 iches of the ground?????????
I won't ba able to get in my drive way like that.
:grd: :grd: :grd:

Easier to trim than add. :)

Mcrat

Will that induction hood provide hi-P air to the intake only, or is it venting the entire bay? IOW, does it isolate IAT to a cold air source?

Carhauler, I see you peeking, any new news?

Here is a picture of tonights work. Should finish up in a night or so. It will hang about 5" below the lower valance on the bumper. Let me know what you think so far. I need to trim the ends and install end supports. It is made out of 1/8" steel.http://img79.imageshack.us/img79/2564/jhghfr0017ih.th.jpg (http://img79.imageshack.us/my.php?image=jhghfr0017ih.jpg)

Are you going to block the area above it to the bulkhead?

Fingers, you tell me. Should I block above the bulk head? I am just giving this a try and will test it this weekend on a light run just to see if the fan will stay off more or not.
Dan

Mcrat

Will that induction hood provide hi-P air to the intake only, or is it venting the entire bay? IOW, does it isolate IAT to a cold air source?

It's just a Cold Air Intake taking air from the base of the windshield. Still trying to find a couple of parts.

Fingers, you tell me. Should I block above the bulk head? I am just giving this a try and will test it this weekend on a light run just to see if the fan will stay off more or not.
Dan

Block it. Doesn't have to be steel.

Opening the hood at the windshield base will create more high pressure under the hood, which you don't want. Even if it didn't, you would flood your heating/cooling ducts with hot air. You don't want either scenario.

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Thx Tx. I was thinking along the same lines as River&Sand, but obviously you are correct. My impression is that there is a huge air dam created by the combination of the stack and fan clutch, part of which GM considers to be positive because it retains the heat, reducing NOx, etc. But what I've been wondering is where does the air go after it gets past the stack? Are the air exit paths restricted driving down the delta p? My gut says no, it flows freely out the sides of the engine and underneath the pan. So this may be a stupid question, but is there anything we could do to increase delta p by clearing an exit route for the air flow?

Call me stupid. I can take it.

Ed

Thx Tx. I was thinking along the same lines as River&Sand, but obviously you are correct. My impression is that there is a huge air dam created by the combination of the stack and fan clutch, part of which GM considers to be positive because it retains the heat, reducing NOx, etc. But what I've been wondering is where does the air go after it gets past the stack? Are the air exit paths restricted driving down the delta p? My gut says no, it flows freely out the sides of the engine and underneath the pan. So this may be a stupid question, but is there anything we could do to increase delta p by clearing an exit route for the air flow?

Call me stupid. I can take it.

Ed

Hey stupid (all stupid people are welcome)

Good thought. I want to reply. Look again at the fan while it is running. Direction of flow, straight to the engine, shaped just like a wall. I bet there is a ton of turbulence there. That has got to retard flow (increase P). Unfortunately, I can't see much to improve it. If some type of gentle curve could be attached to the hood, or fan shroud (lightbulb) so as to deflect all flow down, and eliminate the engine block spash, that would help. There is so little room there. The advantage to the IAT is obvious also.

If the fan shaft was extended 2", and the shroud trimmed a bit, that might make a little room.

dwrat, with the ABS piece back on there are two large holes in it where the tie down hooks poke through. Lots of air can get through those holes. Did you plug them as well? The reason I mention that is looking at your picture you can see that the plastic shield sits right behind them.

Are we underestimating just how important that flimzy POS flap is right under the stack? It appears to be the only thing between the stack and the ground holding positive pressure on the front of the stack. When the dealer installed my fog lights they pushed the flap down below the bottom of the bumper, it should rest inside the bumper, even better affixed in line with the vent holes in the bumper. I suspect my truck was pushing air down/away from the stack versus through it. Additionally, that plastic sheild underneath may actually have prevented cooler air from entering the stack from below, or raised the pressure under the hood. As evidenced by Rick's runs something is different without that shield.

I'm anxious to see Fingers runs with his new dam. Fingers, if you've already posted any mods you have I missed them or just having a senior moment. We need to have all the variables on the table so we compare "apples to apples". JJ

The fan actually creates its own enemy (pressure) it pumps so much of its air up into the airbox/fender area that you can actually feel it blowing out the crack between the hood and passenger fender.

Makes me wonder if a reverse rotation and blade layout would send it out the other corner, which would be out under the truck on the drivers side.....perhaps it would only pump it to the other fender corner, who knows......

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I fortunately haven't overheated yet, but I haven't towed anything heavy either. But to follow up on the hood issue. What about thermostatically controlled hood louvers? We would just need the hood map to figure out how big, and a good place for them to mount.
Just some input..
Ricky...seeya...

I've got a post over on the LB7 engine forum, to have those guys check and see if the fan on those engines also dump on the airbox. There has to be something that directs that flow off the front of the engine, as I can't see anything unique about the shroud that would cause it.

Eyeballing it, the only thing that seems obvious is the tensioner pulley.

We know this is not the root cause of the overheating problem, but it has to be a contributing factor.

AC:

say 3 tons at R=3 (lots of duty and not very efficient, a house is typically 4 to 5 tons, and the biggest 110V window unit is about 1 ton). ==> 4 tons of heat load, 1 ton=12000 BTU/hr, so a high estimate of condenser heat load would be 48000 BTU/hr



cit, I like your calculations but how do you estimate the BTUs for the A/C that high? 48000 BTUs can cool a small 1600 sqft home which has a 100 times bigger air volume to cool. Even if the A/C in the car is much less efficient and might have a higher duty cycle I doubt it will ever produce even 12000 BTU of heat - so its negligible compared to IC and Engine Cooler IMHO

The fan actually creates its own enemy (pressure) it pumps so much of its air up into the airbox/fender area that you can actually feel it blowing out the crack between the hood and passenger fender.


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Some of my short runs with the fan engaged show that the fan pressurises the area under the hood in excess of the pressure at the air box w/o the dam. The fan hasn't stayed on long enough for me to pull good numbers. Without the fan engaged, there appears to still be a pressure differential, but it is very hard to measure.

The fan creates a phenominal amount of differential across the stack by itself. I have measured well in excess of 2 iw sitting still. Wish I could keep the darn thing engaged without heating up.

cit, I like your calculations but how do you estimate the BTUs for the A/C that high? 48000 BTUs can cool a small 1600 sqft home which has a 100 times bigger air volume to cool. Even if the A/C in the car is much less efficient and might have a higher duty cycle I doubt it will ever produce even 12000 BTU of heat - so its negligible compared to IC and Engine Cooler IMHO

Not a complete answer but one differences worth noting is the truck A/C cools outside air down to about 65 or less on a continuous basis. House A/C only has to temper the air a few degrees. Ever notice how long it takes to cool down a hot house? 48,000 may be high, or even low, but it is close.

Hey stupid (all stupid people are welcome)

Good thought. I want to reply. Look again at the fan while it is running. Direction of flow, straight to the engine, shaped just like a wall. I bet there is a ton of turbulence there. That has got to retard flow (increase P). Unfortunately, I can't see much to improve it. If some type of gentle curve could be attached to the hood, or fan shroud (lightbulb) so as to deflect all flow down, and eliminate the engine block spash, that would help. There is so little room there. The advantage to the IAT is obvious also.

If the fan shaft was extended 2", and the shroud trimmed a bit, that might make a little room.

After my last post, I thought to go out and actually look at the situation. Wow! The stack is more than I imagined! And between it, the fan shroud, the fan clutch, the fan blades, and the engine face immediately behind it, the design appears to be an air pressurization system rather than a cooling system. At any speed other than idle, the fan clutch should allow the fan to turn freely (even a freewheeling fan has a lot of air resistance - think autorotating helicopter). We'd be better off with something like the sailboat guys have on their props - folding (feathering) blades to get the h*** out of the way when airflow exceeds the fan's capacity. If they can do it for water, we sure should be able to do it for air. Oh, also for the record KB, a funnel shaped deflector (narrow end forward) mounted on the front of the engine would do a lot to improve the airflow. The front could protrude between the belt and drives all the way to the fan hub. (Theory, not design.)

I think I have the fog lights mentioned by JJ, but I believe they were factory installed. But just like his, my POS flap (is it plastic or is it memorex?) had been pushed down so that it was almost vertical with air being directed out the front of the compartment under the front bumper. Now THAT IS stupid, even I know that much. I repositioned it so that it's laying on top of the lower air dam support about an inch below the rectangular holes in the bumper, but it would be better if it were actually fastened down with the plastic nut gadgets that hold the lower air dam. I tried to get one out, but it was a real PITA. Apparently GM doesn't secure it because they would have to put four holes in the flap!

For the record, the flap is embossed with the following - CHEVY 15187923. I thought it was one of those cardboard things that evaporate in the rain. I'm going to keep my eye on it though.

Thanks for the welcome.

Ed

Not a complete answer but one differences worth noting is the truck A/C cools outside air down to about 65 or less on a continuous basis. House A/C only has to temper the air a few degrees. Ever notice how long it takes to cool down a hot house? 48,000 may be high, or even low, but it is close.
I agree in part but the huge temp difference appears only when the car is very hot inside. When cruising and using recirculation the temp difference is similar to a house and the heat produced than is small. If 1KW compressor capacity equals 3413 BTUs/h than that compressor must be huge for 48k BTUs. (normal compressor maybe 5..7 KW)
But thats all NOT that important. Just wanted to point out that the A/C is not causing any significant heat increase to the stack compared to IC and Engine Cooler...

i dont know if it has been said or not i dont want to read 11 pages of this but why not try a cawl indected hood to get some air in there? if that dosnt work and least they look good

Should have taken the time. It was discussed 3 pages ago.

For the record, the flap is embossed with the following - CHEVY 15187923. I thought it was one of those cardboard things that evaporate in the rain. I'm going to keep my eye on it though.
Ed

You'll find that the first time you exceed about 60 MPH, it'll "flap" back down. I took this to mean that it does a good job of increasing stack inlet pressure at speed...if it would stay put.

On mine I had to poke holes in it, and zip tie it to two of those fiddly plastic fasteners.

I agree in part but the huge temp difference appears only when the car is very hot inside. When cruising and using recirculation the temp difference is similar to a house and the heat produced than is small. If 1KW compressor capacity equals 3413 BTUs/h than that compressor must be huge for 48k BTUs. (normal compressor maybe 5..7 KW)
But thats all NOT that important. Just wanted to point out that the A/C is not causing any significant heat increase to the stack compared to IC and Engine Cooler...

My hidden-agenda was to show how small the condenser and IC heat loads are compared to the radiator. That's why I used worst-case conditions for both.

And, for the record, I assumed 3 tons (36000 BTU/hr) of refrigeration. The other ton (basis R=3) is from the compressor work. Buy 1, get 3, reject 4. Think of the 1 as Prof. Carnot's tax.

And, your house unit operates are R values of 10 to 14 (I hope!).

I have found that flap to be a most excellent escape route for air that otherwise might pass through the stack, and the fact it gets blasted (or sucked) back down (mine behaves like yours) is a good sign of what is happening. It would seem it exposes the face of the stack to the low pressure air passing below the bumper......

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cit calculate radiant heat off the IC imposed on the radiator.

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If I could make a mod as a shot, it would be to trim a bit off the fan shroud, like to that first ring, install another row in the radiator, and move the radiator away from the IC til the shroud was back halfway over the fan.

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It is hard to imagine GM would bank on such a flimzy flap to stay in place and support the stack. Maybe it is there just to keep debris away from the stack? Anybody know its exact purpose? JJ

The size of the condenser alone could not support 2 tons. But it is mute, as we all agree that it is negligible compared to the rest of the load. BTW, the stack order is for a reason, the lowest load first.

Bettered, i hope you didn't take offense, just playing. You made a lot of sense. We will eventually have to focus on front P for improvement.

I would encourage anyone to get a magnehelic gauge, one graduated for 2-3 iw, and play with it. THAT will save so much time. One the front end flow, most preconcieved ideas get tossed, almost nothing is as you would intuitively think.

Search Ebay.

I have found that flap to be a most excellent escape route for air that otherwise might pass through the stack, and the fact it gets blasted (or sucked) back down (mine behaves like yours) is a good sign of what is happening. It would seem it exposes the face of the stack to the low pressure air passing below the bumper......

.

So we have a bunch of positive pressure on top with no real pathway for air flow other than down, and a bunch of negative pressure underneath (behind the air dam). No wonder the flap flops. Some whiz kid design?

I'm going to give those plastic nut thingies that hold the air dam in place another go. See if I can get them off, poke some holes in the flap and reinstall the flap constrained by the plastic nuts. I might even try and capture it between the bumper and the air dam. Then I'm putting some duct tape (actually, the aluminized foil style) over the large hole where the tubes from the trans cooler are routed. Surely they don't need that much space... Since my truck is pretty new, there's not a lot of dirt to prevent adhesion..

Ed

cit calculate radiant heat off the IC imposed on the radiator.

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After looking at that cooler I thought exactly the same thing, but is it significantly different from the LB7?

Ed

It is hard to imagine GM would bank on such a flimzy flap to stay in place and support the stack. Maybe it is there just to keep debris away from the stack? Anybody know its exact purpose? JJ

for a fact,no. But I have to think it is to increase front P.

After looking at that cooler I thought exactly the same thing, but is it significantly different from the LB7?

Ed

Whoopsie, come again? Different IC?

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TxC, I was thinking along the same lines except to cut the bottom of the shroud at an angle towards the drivers side, sort of like a channel for air flow to follow.

Question: That shroud doesn't appear to direct air in any particular direction, so why does the fan choose to discharge it at the right front fender? Less pressure, rotational velocity, ???? If there were a way to divert that air down/away from the engine compartment we'd eliminate a lot of hot air from the air intake and other components under the hood.

Along with the air dam, I for one would rather have the heat out from under the hood and stick with the stock air intake. Whichever approach is taken, cooler intake air seems critical to fixing this. JJ

Whoopsie, come again? Different IC?

.

Same IC as LB7

The fan ejects air radially as much if not more than to the back, with a slight rotation. The two obstructions to this flow are the hood and the splash guard. Makes sense that just past these two you feel the most air. Besides the air box area, check the driver's side just inside the tire. Heck of a breeze there, but not nearly as much on the passenger side..

The size of the condenser alone could not support 2 tons. But it is mute, as we all agree that it is negligible compared to the rest of the load. BTW, the stack order is for a reason, the lowest load first.

Bettered, i hope you didn't take offense, just playing. You made a lot of sense. We will eventually have to focus on front P, for now looks like our hands are full.

I would encourage anyone to get a magnehelic gauge, one graduated for 2-3 iw, and play with it. THAT will save so much time. One the front end flow, most preconcieved ideas get tossed, almost nothing is as you would intuitively think.

Search Ebay.

You are you saying the intercooler load is lower than the engine coolant load? That would seem to me to be in question. That thing is HUGE! Maybe it's time for GM to think about deeper, narrower coolers and put them side by side so the cooling air is not pre-heated by lower (but not trivial) loads.

No offense taken KB. I'm one of the worst leg pullers you've met. Usually it's me who's stirring the pot. I do like to play.

But I am serious about this 'pressurized compartment' notion. In the old days, it was air flow and there was plenty of room around in the compt. It looks today like we may be into pressurizing the compt, and letting the air escape anyway it can, which is not always in our favor. And I do appreciate the work that is underway.

WTH, I'm a project manager. Just get more ants.. Bill the customer. No sweat. That way it doesn't even matter what the rates are..

Oh, volunteers? Hmm. How do you get more blood out of the stone? I found that squeezing isn't effective.

Keep up the great work, guys.

Special kudos to Fingers. I read the entire stick / block plate thread yesterday. Took all day! Now I'm looking for that spot where the plate goes - back near the firewall I think. BTW, I unplugged and then pushed the connector back on a little bit. Enough to look good, not enough to engage. Probably dropped some codes, but no light - so far. Engine seems to rev more freely.

Ed

bettered, I used the metal/foil tape with success, so far. I've ran the truck several times at 70-80mph, high humidity and rain and so far so good. Just be sure to clean the bumper and stack surfaces real good, I used alcohol just before attaching the tape for a good seal. Don't skimp, and use criss-cross strips where they attach to anything structural. Also put some on the underside for stability. I really should take some pictures, sorry! I'll see what I can do. I have a brush grill to remove which is a PITA. Oh yea, plug the hole beside each fog light to.

In no way do I consider this a permanent fix, but for testing purposes it will do. Like I posted previously my ECT's drop like a rock now, but for slow/city driving the stack still sucks big time. I'm going to stop by a couple of body shops to get their ideas on fabricating something for some trials. Hopefully they'll have some spare materials lying around so $$$$ is saved. I got my eyes on those TTT mirrors! lol JJ

Same IC as LB7

So the IC is not a new contributor to the problem, and calculating its heat load isn't going to give us a new pathway to pursue. Just additional information.

Ed

Ed,

Air to air cooling is very difficult. You have to keep the air to be cooled in the exchanger a long time. Thus the size of the IC. But as CIT spelled out, the loading from the IC minor compared to the Radiator. Not insignificant, but minor.

As an asside, lack of flow would decrease the cooling of the air charge going through the IC.

I can not find RDL's post on which temp sensor probes he is using and where he got them. A little help?

bettered, I used the metal/foil tape with success, so far. I've ran the truck several times at 70-80mph, high humidity and rain and so far so good. Just be sure to clean the bumper and stack surfaces real good, I used alcohol just before attaching the tape for a good seal. Don't skimp, and use criss-cross strips where they attach to anything structural. Also put some on the underside for stability. I really should take some pictures, sorry! I'll see what I can do. I have a brush grill to remove which is a PITA. Oh yea, plug the hole beside each fog light to.

In no way do I consider this a permanent fix, but for testing purposes it will do. Like I posted previously my ECT's drop like a rock now, but for slow/city driving the stack still sucks big time. I'm going to stop by a couple of body shops to get their ideas on fabricating something for some trials. Hopefully they'll have some spare materials lying around so $$$$ is saved. I got my eyes on those TTT mirrors! lol JJ

I'm going to take your advice and go after the front end pretty much as you've done. Thanks for the suggestion on the fog light holes. But you really got to me with the TTT mirrors... I haven't figure that one out yet..

My new truck was fitted out for a 5er so it has the electric extending mirrors. Have yet to tow - probably next week. Doesn't have the drop down feature in reverse or the folding features, but with a bubble butt, the mirrors aren't the biggest problem I have.

Hmmm. TTT mirrors. I'll be thinking about that one..

Ed

Ed,

Air to air cooling is very difficult. You have to keep the air to be cooled in the exchanger a long time. Thus the size of the IC. But as CIT spelled out, the loading from the IC minor compared to the Radiator. Not insignificant, but minor.

As an asside, lack of flow would decrease the cooling of the air charge going through the IC.

I can not find RDL's post on which temp sensor probes he is using and where he got them. A little help?

And as I recall the eq for Q puts a lot of emphasis on delta T - which we don't have a great deal of on a hot day.. OK, I understand the IC better now. Thanks Fingers.:ro) :bow: :bow: :bow:

bettered, don't want to get off track on this thread, I'll PM you later re the TTT's.

Fingers, good intel! What do you guys think would happen if we extended the upper half of the fan shroud and left the bottom a bit shorter? Too much turbulence? Just thinking as the air rotates through the shroud it will exit through the bottom once it leaves the shroud. Simple question, though I suspect there's a bunch of engineering stuff that goes with it. If the answer is a simple no, won't work, that will suffice. No need to get into something hair-brain. Just thought I would ask. JJ

http://dieselplace.com/forum/showthread.php?p=621016#post621016

Fingers, here ya go. JJ

I can not find RDL's post on which temp sensor probes he is using and where he got them. A little help?

Don't know if this link will paste correctly, but you can get to the main site:

http://www.professionalequipment.com...qx/default.htm (http://www.professionalequipment.com/xq/ASP/ProductID.1154/id.22/subID.174/qx/default.htm)

cit calculate radiant heat off the IC imposed on the radiator.

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I does not matter how heat gets from the IC to the rad, either by convection of the moving air, or by radiation. There's only so much of it to move, and it's much less than the heating of the rad by the circulating coolant.

But, if you really want to know, 5.4 ft2 of aluminum (Face area only, unpolished, emissivity=0.07, from the Bosch Automotive Handbook), at 450F, will radiate a total of 129 W, or 442 BTU/hr.

The radiator (at 210F) actually radiates more toward the IC, because it's black. Subtracting the unreflected radiation coming from the rad, you get a net rate of about 325 BTU/hr from IC to Rad. Technically, both fluxes bounce back and forth, and you have to iterate, but the 325 BTU/hr will be close.

But, this just means the air between them is a smidge cooler, since photons are helping move the heat. It's the total heat load you need to worry about.

The fan ejects air radially as much if not more than to the back, with a slight rotation. The two obstructions to this flow are the hood and the splash guard. Makes sense that just past these two you feel the most air. Besides the air box area, check the driver's side just inside the tire. Heck of a breeze there, but not nearly as much on the passenger side..

I question this. I wouldn't expect THIS fan to eject radially. But clearly the air must go somewhere, and under the hood is going to be hi-P, you definately can feel it squeezing through the hood cracks..

Numbers this weekend, I promise.

bettered, don't want to get off track on this thread, I'll PM you later re the TTT's.

Fingers, good intel! What do you guys think would happen if we extended the upper half of the fan shroud and left the bottom a bit shorter? Too much turbulence? Just thinking as the air rotates through the shroud it will exit through the bottom once it leaves the shroud. Simple question, though I suspect there's a bunch of engineering stuff that goes with it. If the answer is a simple no, won't work, that will suffice. No need to get into something hair-brain. Just thought I would ask. JJ


Better to isolate the Air box from the rest of the compartment. A cardboard divider would suffice for testing.

You are you saying the intercooler load is lower than the engine coolant load? That would seem to me to be in question. That thing is HUGE! Maybe it's time for GM to think about deeper, narrower coolers and put them side by side so the cooling air is not pre-heated by lower (but not trivial) loads.


Ed, yes it is huge. I went into the design parameters and functions of various heat exchangers on the OH thread.

It has to be huge. It get's one shot to cool charge air, batch cooling. Water holds 1000 times the energy of CAC air, the energy offloaded is vastly different because one is air-air, the other air-water. Plus the radiator is a recycle process, if the first pass doesn't do it, the coolant will be coming around again.

But what is revealed, is that if air flow is low enough, that CAC will input pretty hot air to the rad at 20+ boost. So, in a sense, you might consider the CAC too large. Bear with me.

If it were smaller (or not there at all, forget the consequences of that for a minute) then the air leaving the CAC stage would be significantly cooler for the rad.

The beneficial aspect of a larger CAC, if it weighs more, it will be a better heat sink, which as we know, can absorb transient spikes in thermal production. Then release it over time. i don't see it helping here, the overheats are on pulls long enough to exceed the heat sink characteristics of the largest CAC's.

Folks, we are more or less stuck with a finite amount of front end, without cutting off the entire nose. The only reason I could see to replace a heat exchanger, is if it had poor restriction internally, or in the fins.

I does not matter how heat gets from the IC to the rad, either by convection of the moving air, or by radiation. There's only so much of it to move, and it's much less than the heating of the rad by the circulating coolant.

But, if you really want to know, 5.4 ft2 of aluminum (Face area only, unpolished, emissivity=0.07, from the Bosch Automotive Handbook), at 450F, will radiate a total of 129 W, or 442 BTU/hr.

The radiator (at 210F) actually radiates more toward the IC, because it's black. Subtracting the unreflected radiation coming from the rad, you get a net rate of about 325 BTU/hr from IC to Rad. Technically, both fluxes bounce back and forth, and you have to iterate, but the 325 BTU/hr will be close.

But, this just means the air between them is a smidge cooler, since photons are helping move the heat. It's the total heat load you need to worry about.


Wow!!! :eek: School was a long time ago (and I really didn't like all that thermo / heat transfer stuff anyway). But this was a real eye opener. Thanks CIT. I needed that.

Ed

At any speed other than idle, the fan clutch should allow the fan to turn freely (even a freewheeling fan has a lot of air resistance - think autorotating helicopter).

Do you realize that, by design, the fan is always pulling something, and must? The air it moves (across itself) is what engages and disengages it.

But I love the idea of electric, or electro-viscous, and the advantages you mention

edit: disregard: I misread your post

I question this. I wouldn't expect THIS fan to eject radially. But clearly the air must go somewhere, and under the hood is going to be hi-P, you definately can feel it squeezing through the hood cracks..

Numbers this weekend, I promise.
All fan shrouds I have seen are built that way - about half way covering the fan blades. This is for easy discharge of hot air and for fan noise. A longer shroud would channel the air against the engine block and cause more backpressure the fan has to work against. Altering the shroud design would also increase the noise - its damn noisy enough the way it is now.

To really help cooling a very easy way would be to engage the fan earlier (by changing the fluid clutch parameters) - like its done in hotter climates than the U.S. (Middle East). I have lived with permanent fan noise for a long time - its not nice to hear...

I does not matter how heat gets from the IC to the rad, either by convection of the moving air, or by radiation. There's only so much of it to move, and it's much less than the heating of the rad by the circulating coolant.

But, if you really want to know, 5.4 ft2 of aluminum (Face area only, unpolished, emissivity=0.07, from the Bosch Automotive Handbook), at 450F, will radiate a total of 129 W, or 442 BTU/hr.

The radiator (at 210F) actually radiates more toward the IC, because it's black. Subtracting the unreflected radiation coming from the rad, you get a net rate of about 325 BTU/hr from IC to Rad. Technically, both fluxes bounce back and forth, and you have to iterate, but the 325 BTU/hr will be close.

But, this just means the air between them is a smidge cooler, since photons are helping move the heat. It's the total heat load you need to worry about.

Questions:

Your calculations on the radiator BTU's would seem excessive, not 100% of the 310 hp is being cooled by the radiator. Temperature drops across the radiator would seem roughly 50*, yet we have underhood temps at 221*

Would seem that a large part of the heat generated by the engine is being shed by metal surfaces of the engine itself, thereby reducing the (calculated) BTU load of the radiator.

Also, if the IC is only handing off 325 BTU's/hr to the radiator, where are the other 160,000 going?

Also, what is the calculated load on the engine from the heat piped into it via the piping from the IC into the intake?

.

I don't have the over heating problem but I really have sympathy for those that do. I just had a thought that I wanted to share. If I were having this problem and not getting any help from GM, I think I would pick a time that I could afford some down time and hook it up to the biggest load the truck is rated for and head for the hills. When the sucker blows GM has no choice but to deal with it then. If it doesn't blow then maybe readings aren't that accurate or the truck can actually handle the extra heat. Anyway, I really hope for all our sakes ( resale down the road ) that this issue gets resovled, and soon for those having the problem.

Question: That shroud doesn't appear to direct air in any particular direction, so why does the fan choose to discharge it at the right front fender? Less pressure, rotational velocity, ???? If there were a way to divert that air down/away from the engine compartment we'd eliminate a lot of hot air from the air intake and other components under the hood. JJ

JJ,

The fan is not symetrically located in the center of the truck. It is closer to the air box than to the driver side. I think there is more obstruction to air flow on air box side and that is why air ends up being deflected upwards and towards the air box.

I have an LB7. Oilbrnr posted a note on the LB7 discussion board. I was suprised at the air movement (with the hood up of course). There is a clear pulsing of hot air over the top of the air box, while the drivers side is much quieter in a large area around the battery.

It would seem the radiators actual workload is the 50* drop it provides. Thats the BTU's it handles, the rest are returned to the engine.

The demand on the radiator cannot be 310hp of heat.

.

I have an 03 calif LB7, and had some heat probs a while back, so Ive been following the OH and this thread. My problems stemmed from a plugged catalytic convertor, causing high EGT's and ECT's. Blocking the EGR with Fingers-style plate (thanks for the heads-up), and replacing the entire exhaust system solved the problem. However; it didn't take much in the way of increased heat load to push my LB7 over the same wall you guys are seeing, and I started looking at what could help increase the efficiency of the stock cooling system. I think Fingers and JJ are heading down the right road. Getting more air through the stack is a priority, and then getting it out of the engine compartment is next. That where I might be able to contribute, I hope.
In addition to blocking the holes in front of the stack, and adding an airdam to keep air out from under the truck, a couple small things could help get the air out of the engine bay.
One way of pulling air out of the eng.comp. is to utilize the slight low pressure area in the front of the wheelwell. Trimming or moving the fenderliner away from the frame will give the air some more space to flow thru, and if you add a small lip to the forward edge of the fender, in front of the tire, this will help direct airflow past the tire. Right now, the back edge of the fender sticks out farther than the front, so it will 'scoop' air into the fenderwell- adding this lip at the front sort of sends the air out away a little farther, so not as much gets caught. It would look sort of like a mudflap, only on the front of the fender instead of the back. Look at the front of most racecars with fenders, and you'll see that they do something similar.
Fingers mentioned putting a piece of cardboard between the fan shroud and the air filter box- if you curve that piece of cardboard and slip it under the intake hose, and send it down beside the airbox, that might help direct the radial flow off the fan down toward the opened-up fenderliner. The fan is supposed to throw off a lot of flow radially, that's why the back of the blade sticks out of the shroud. If it was fully enclosed, it blades would probably stall when the air backed up against the engine. Then there REALLY wouldn't be any flow across the stack!
I have done some of the things JJ has done to try and get more flow thru the stack, and I have moved the fenderliner away from the frame with small pieces of wood. Like JJ, I noticed little effect at slow speeds, but anywhere above 30, if it heats up enough for the fan to come on, it draws the temps down quicky and shuts off, and hasn't allowed temps to exceed 210. For my particular truck, this is an improvement over how it reacted to heat even before the cat plugged up. I think an airdam and fender lips will improve it even more...
I never considered the fan flow heating up the airbox till I read this thread, so I will try and fashion an 'air-director' and see if I notice any diff.
Hats off to all of you contributing to these threads!

Take a look at a posting in the Allison OEM section. "06 with a 06 speed alli."

Author states that the Air filter, Air Box, Eng Fan, and Fan shroud have all changed!!

I've been keeping up with this thread even though my truck doesn't overheat. I had an idea, but not sure if it would work. Could you somehow mount a maf sensor ( round one like on the gas motors) in the grile and one behide the fan to see how much air is really going through there?

There are also some underhood pictures on the "Saw/drove an 06 today". He doesn't mention if it is a GMC or Chevy though. I'm going to look on GMBuyPower.com to see if there are any 06's on the lots in Jacksonville. If there are I'll go look at one up close and personal.

Looks like they have changed the airbox, fan and cowling. Curious to see if they made any changes to the stack and front air dams. Wouldn't surprise me if they went to school on our posts. JJ

Take a look at a posting in the Allison OEM section. "06 with a 06 speed alli."

Author states that the Air filter, Air Box, Eng Fan, and Fan shroud have all changed!!

Sounds like an admission of guilt on GM's part. Why else would these items need to be changed in the final model year? :rolleyes:

I would venture to say that the greatest BTU handler involved in the LLY is the exhaust. Whats the amount of heat being crapped out there?

.

Questions:

Your calculations on the radiator BTU's would seem excessive, not 100% of the 310 hp is being cooled by the radiator. Temperature drops across the radiator would seem roughly 50*, yet we have underhood temps at 221*

Would seem that a large part of the heat generated by the engine is being shed by metal surfaces of the engine itself, thereby reducing the (calculated) BTU load of the radiator.

Also, if the IC is only handing off 325 BTU's/hr to the radiator, where are the other 160,000 going?

Also, what is the calculated load on the engine from the heat piped into it via the piping from the IC into the intake?

.

The BTUs shed by the engine surfaces are minimal. Not much area and poor air flow. If you see 221 when the ECT is 200, it is the exhaust and turbo radiating into stagnent air. Better air flow under the hood would still be a good thing.

YOU asked what the *radiant* heat transfer was between IC and Radiator. 325 BTUs does not include the heated air. Provided the air does not exceed the Rad temp, The IC does not add BTUs to the Rad.

Thanks for the links JJ and Oilburner.

It would seem the radiators actual workload is the 50* drop it provides. Thats the BTU's it handles, the rest are returned to the engine.

The demand on the radiator cannot be 310hp of heat.

.

This is an off the cuff observation, not a scientific response, so don't crucify me if I'm wrong - I often am.

The modern combustion engine almost NEVER operates at more than 20% efficiency, that is in extracting all the available energy from the fuel, converting it to heat (combustion) and then to rotational energy. That leaves about 80% of the fuel's energy wasted - primarily in the form of heat. It's no longer in your fuel tank, it must be going somewhere. When you compare your engine's output to one component of the lost value of heat produced, it's indeed startling, but in perspective it may not be wrong either. Obviously it's not a part of the 'useful' output of the engine. But that it is a significant component of the lost "energy of conversion" we live with.

Nor is electricity a lot better. It's better because of economies of scale and control of the conditions of combustion, but about the best we've done there is 50%. Sure, an electric moter is 95% efficient, but getting the electricity to it (from some fossil fuel) certainly has a LOT of inefficiencies.

It is indeed possible that the radiator blows away 310 hp. And I could be wrong, but maybe I'm not...

Ed

I would venture to say that the greatest BTU handler involved in the LLY is the exhaust. Whats the amount of heat being crapped out there?

.

You are quite right Tx. The answer is most of the 80% you weren't able to use.

Ed

Looks like they have changed the airbox, fan and cowling. Curious to see if they made any changes to the stack and front air dams. Wouldn't surprise me if they went to school on our posts. JJ

If that's true JJ, then they've been doing it for a long time. GM doesn't do very much of anything very quickly.

Ed

The BTUs shed by the engine surfaces are minimal. Not much area and poor air flow. If you see 221 when the ECT is 200, it is the exhaust and turbo radiating into stagnent air. Better air flow under the hood would still be a good thing.

YOU asked what the *radiant* heat transfer was between IC and Radiator. 325 BTUs does not include the heated air. Provided the air does not exceed the Rad temp, The IC does not add BTUs to the Rad.

The 221* was IAT.

I was mostly questioning the BTU's handled by the radiator, which I think he calculated as the hp of the engine. That would not be correct, the radiator is not exposed to 100% of the 310hp of heat therefore is not 80% of the 100% of the BTU's the stack handles.

I could be wrong, its happened before :)

.

What cit was saying, and it is not the first time I have run across it, is that if you get 310 HP out the shaft, you will also be shedding about 310 HP out the exhaust and 310 HP through the cooling system at the same time. This says that your engine is 33% effecient at converting heat into rotational energy. 33% isn't that bad for a thermal engine. Total energy consumed would be on the line of 930HP

What cit was saying, and it is not the first time I have run across it, is that if you get 310 HP out the shaft, you will also be shedding about 310 HP out the exhaust and 310 HP through the cooling system at the same time. This says that your engine is 33% effecient at converting heat into rotational energy. 33% isn't that bad for a thermal engine. Total energy consumed would be on the line of 930HP

Once upon a time I could have run a heat balance and calculated the BTU's available in the fuel, and then based on mpg and speed run some numbers to arrive at conversion efficiency. If it's 33%, I'd be surprised, but pleasantly so.. You're right, 33% would be damn good!

Ed

Still, shouldn't the BTU's of the radiator not be measured by the engine output but instead by what it actually handles? A ton of thermal energy is being eaten just keeping 24 quarts of coolant at a constant 205*.

The radiator is only responsible for the drop it provides to the water that crosses it, which is a small portion of the overall coolant available at any given time. The block, heads, pump, hoses etc hold more than the radiator.

All I am saying is that the BTU load earlier may be highly exagerated especially considering the radiator is one of the lowest temperature items in the whole shebang, I would pick it first if I had to put my hand on one of them.

.

Tx,

Your right. Ultimatly we have to measure the radiators rejection capacity. The quick calcs to bracket how much is expected are good for putting things in perspective. Testing the rad does require some harder to get measurements. We can do it with coolant inlet, outlet temp and flow measurements. Or we could do Air inlet, outlet temp and flow measurements. I am not set up to do the flow measurements on either media. To keep us honest, we have to measure actual and not advertised flows.

BTW if we indeed are getting 50* drop across the rad, we may have a flow problem in the block.

Ah-ha, I asked Goodrych over on the Allison OEM 6 speed post if the airbox was open to underhood air. Here is his response:

I cannot see any openings to engine comp. It looks like it is sealed to inner fender and poss another opening on bottom.

I want to know more about this airbox/shroud/fan change on the '06 and if it can be retro'd to the 4's and 5's. If it can, it seems like we should be able to force GM to at least do this as a TSB.

Does anyone have access to an infrared camera? I used to do thermal imaging of electrical substations using an infrared camera. Using an IR camera would certainly pin point any hot spots and give an accurate measure of the suface temps.
My $.02,
Ben
Here is a link to what I am talking about.
http://www.flirthermography.com/success/image_gallery.asp

Does anyone have access to an infrared camera? I used to do thermal imaging of electrical substations using an infrared camera. Using an IR camera would certainly pin point any hot spots and give an accurate measure of the suface temps.
My $.02,
Ben

Not a bad idea, would need to remote mount and take the shots while working the vehicle.

.

Not a bad idea, would need to remote mount and take the shots while working the vehicle.

.
Considering the price, $50,000+, I think you may be able to get usable images if you could stop while it is OHing.
Ben

I simulated the truck at higher accuracy (more cells). Total number crunching time was up to about 3 hours per run. I ran it with and without an Ghetto Dam (tm).

Nice work Fingers. I looked at the average underside pressure in a square region just under the engine. The air dam (at 70 MPH with 100F air at sea level) reduced the average pressure in that zone by 0.5 to 0.6 inH2O...in reasonable agreement with the data shown so far.

The dam also increases the air pressure under the bumper which should help stop the air leaks from the stack inlet out toward the bumper.

The aft component of force on the dam is about 44 lbf (at only 70 on a hot day). It will be much higher on a cold day at 90 MPH. So it better be fastened well.

Total aerodynamic drag with the dam is 219.7 lbf. Without it's 193 lbf...so it ain't free...over 20% more drag, which makes sense, the frontal area is getting larger.

Aerodynamic lift with the dam is slightly higher, but not much. It's probably due to the higher pressure in front of the dam (it goes from way negative to positive with the dam, and reduced pressure on the hood. I guess this is why racing airdams are at the very front of the body. There's more pitch-up torque too, probably for the same reason...though not enough to lift anything up in the air.

Conclusion is that the dam does add a bit of extra DP to the stack, but costs in drag.

If some of the data seem counter-intuitive, join the club. Sometimes fluid flow just doesn't cooperate with what you think it'll do.

The third pic is the streamlines Fingers wanted.

If the air wants a way out, has anyone tried removing one or both of the plastic fender-well covers? There's a low pressure exit there too.

THANK GOD someone said something new! If I have to read one more post about where HP goes, tailpipe, radiator...dizzy. It is IRRELEVANT! no more.

Hot water in, cool water out, that's all you need to know, and it aint happening.

CIT, I love this stuff you do.

Overall, there are a lot of guys stuck to the keyboard. Go out, get a thermometer, do something to the truck, hitcher up, and head out. There have been lots of suggestions on things to try. Also, you guys who think you can just point to an area, and it must be low pressure, go perfect your lawn dart game, that will be more productive. Here, it is chaff.

A little crude, but let me make the point again, let's do this different, starting with analysis, modeling, a pressure reading or 2, and not work with a blindfold on. I'm not opposed to random experimentation (till I have to cut holes in my hood), but try it before you post any results, as a courtesy to those with the big efforts here.

OTIS, go back and read the first post. You are lost.

Grad school.

Actually you can take a Infra Red photo with a IR filter for about $40.00 or just use IR film from Kodak in a 35 mm camera, or digital.
http://www.adorama.com/HY55RM72.html
http://www.wrotniak.net/photo/infrared/

Using the black and white infrared films the starting point is a red filter (Wratten 25). This filter can be used with an SLR camera and the image composed using the viewfinder. This filter removes most blue and green light but allows the transmission of red and infrared light.

Filters such as the 87C and 87B also cut out some infrared light and are only really suitable for use with Kodak High Speed Infrared film. The use of these filters will affect exposure times; for example, the exposure required for Kodak infrared film using a Wratten 87C filter is four times that for the same film with a Wratten 25 filter.

Visible light ranges from 400 nanometers (violet) to 700nm (red).

So you can't snap the pic as the car passes by you, due to exposure, correct. Can you think of a way this can be used on a moving vehicle (the only way it would have utility)

I was checking the oil today and notice the top radiator hose was completely flat. Is this something that could be causing the overheating?

So you can't snap the pic as the car passes by you, due to exposure, correct. Can you think of a way this can be used on a moving vehicle (the only way it would have utility)

Sure, but it would take two people. Set up a predetermined photo place, and have the photographer pan the camera as the truck drives by. Depending on the photographer's experience, this could come out quite well (it's not that hard, once you get the knack). Even if it's a bit fuzzy, it should still be able to show the hot areas of the truck.

By the way, it's probably best to do this early in the morning, so the background items (houses, streets, signs, etc) haven't had a chance to get heat-soaked.

Joseph

vw23, it's normal. While long, there is plenty of general intel on the original overheating thread. JJ

WARNING!!! READ AT YOUR OWN RISK!!!! SMARTA** REMARK TO FOLLOW!!!

Ok Guys, I have been giving this a lot of thought...and maybe the best soloution to our problems are as simple as reverting to some old fashioned overheating cures.

How about we all buy ourselves a couple of burlap sackls, fill them with block ice and hang them in front of the grill. That should cool the air a bit Huh!!!

"IF YOU FEEL SOME SORT OF STRESS COMING ON DUE TO THE STUPIDITY OF THIS POST, PLEASE REMEMBER TO LIGHTEN UP SOMETIMES, IT IS GETTING WAY TOO DEEP IN THIS POST.

Sorry Guys, had to do it!

John

Sure, but it would take two people. Set up a predetermined photo place, and have the photographer pan the camera as the truck drives by. Depending on the photographer's experience, this could come out quite well (it's not that hard, once you get the knack). Even if it's a bit fuzzy, it should still be able to show the hot areas of the truck.

By the way, it's probably best to do this early in the morning, so the background items (houses, streets, signs, etc) haven't had a chance to get heat-soaked.

Joseph

I was wanting the camera underhood taking pics of the heads and turbo looking for hot spots.

.

Paid advertisement by CBRJohn2000's Ice Company! ):h Always room for a good laugh. ;) Now back to work! :eek: :whip: JJ :)

I was wanting the camera underhood taking pics of the heads and turbo looking for hot spots.

Ouch! Sorry, that's not so easy. Maybe an asbestos towel for the photographer on this one (and no, I won't volunteer)! :) Actually, I just popped my hood open tonight. There's not much room for a camera anywhere in that engine compartment, once you close the hood. I think you're back to your temp probes for this one.

Joseph

Ouch! Sorry, that's not so easy. Maybe an asbestos towel for the photographer on this one (and no, I won't volunteer)! :) Actually, I just popped my hood open tonight. There's not much room for a camera anywhere in that engine compartment, once you close the hood. I think you're back to your temp probes for this one.

Joseph

Oh, I was thinking a remote button to trip the camera, and it seems that the truck could do without a battery on either side temporarily to make way for a camera platform. Who knows.......maybe not possible. I don't have the camera anyway.

.

funny, oh well. Part of me feels guilty I am not running tests. Game officiating instead.

Won a court case today that was over a year in making. Kept me under water all week. I'll make more contributions in the next day or so, some solid numbers. Some of the posts here have given me some new ideas to run pressure tests.

One thing I will test is angle differences: does squatting affect delta P?
I will sample various areas underhood, though this may prove difficult with all that air rotating every which way (any suggestions?).
Will also sample different areas on the grill, wheel well.
Mapping the hood of course

Any other suggestions for the pressure test bed? K.I.S.S. please

My buddy laser cut the pattern for me so I just had to install the prototype.

DP with the new dam and without the valance was up over 3 iw at 75 no fan. Low speed DP was better too. I didn't run with the valance tonight, but it is back on. I hope to tow at 26,000 gross sometime Thursday on the ball buster hill and friends to see what she will do.

Dang Fingers, thats jam up! Good work for sure. Is V3.0 the final?

.

Yes, nice effort man. Those show the imprortance of getting that damn mounted up high. Fit's the GMC? I'll beta test if you like. Small load, I can assess P improvement and fan engagement in our record setting weather. I am also instrumented to test AC efficiency improvement with airflow increase.

That last pic. What are those fender enhancements? Is it the same thing that comes on the LT trim?

Are they removeable? (can you feel me thinking?)

The bushwacker flares?

.

DP? Is that different than Static Pressure? Let's define these terms.

So what you did was just extend the airdam down into "clean" air? Here's hoping that helps. I read on another thread about an 06, and the poster said that it has a different fan and shroud. Why not see if you can acquire those parts and put them on an 04-05 and see if it helps....


The bushwacker flares?

.

Those aren't Bushwackers.....they are a "Finger's Special" :ro) Made them from scratch himself.

He put a heck of a lot of time into those.....they turned out nice.

So if any of you guys doubt he has the capability and the tenacity to solve this OH problem......think again.

Tom ):h

The bushwacker flares?

.

ok, "fingers special". at some point, if they are removeable, we need to see what they did, if anything, to fingers P drop. I didn't see them before. We know a lot is happening in the fender area. That enhancement resembles my flares on the LT. I don't think all trucks come with it. see what I am asking? I'll wait for him to wake up to respond.

I'll look and see if mine are removeable

My dam is done and I will test it out on a small load Saturday just to see if the fan does not come on all the time is it has in the past on the very same run to the Colardo river. The real test will be Thursday the 28th a 6% hill for 17 miles heading to Utah from Phx pulling 10,000 + toy hauler.http://img311.imageshack.us/img311/4348/cxx3ph.th.jpg (http://img311.imageshack.us/my.php?image=cxx3ph.jpg)

My dam is done and I will test it out on a small load Saturday just to see if the fan does not come on all the time is it has in the past on the very same run to the Colardo river. The real test will be Thursday the 28th a 6% hill for 17 miles heading to Utah from Phx pulling 10,000 + toy hauler.http://img311.imageshack.us/img311/4348/cxx3ph.th.jpg (http://img311.imageshack.us/my.php?image=cxx3ph.jpg)

excellent. Remind me which stretch of road that is. Going to Lake Powell?

"So if any of you guys doubt he has the capability and the tenacity to solve this OH problem......think again."

Question is does he have enough finger nails left to "get er' done"! lol Inside joke!
I for one am always glad to see Fingers join in on threads: short, concise, to the point! Not like some other people on the DP? J/K Look who's talking? lol

OK back on track. cit1991's post jives with what someone else posted about placing some strategic vent holes/openings in the wheel wells since there appears to be very low pressure there. Appears fairly easy to try and repair if no noticeable difference. Along with the air dam increasing +p and decreasing -p under the hood the truck might suck air like a vacuum cleaner!

dwrat, nice job. Did you block the front end, can't tell that by the pictures. Specifically what I'm curious about is have you blocked off any air from entering the stack and bumper vent areas so it can't flow down/under the truck? POS flap securely in place? We don't want pressures working against each other. Either flow air through the stack or get it pushed to the side and away from the front of the truck, correct? Are all your engine/tranny mods in your signature? Covering the bases!

TheBac made a good suggestion about getting a hold of those new parts for the 06's and strapping them onto a 04.5 or 05 that runs hot. Anyone know what that little box is on the back of the new fan shroud? Someone mentioned a CPU? Looks like a small electric fan to ol JJ. Maybe a booster fan for increasing stack flow at lower speeds? Coupled with the viscous fan we have now that just might work! Pretty small though. Anyone know what it is? JJ

I read on another thread about an 06, and the poster said that it has a different fan and shroud.
Tom ):h

More, more...? Is it Electro viscous?

[quote=JJs DuMax;634342 Anyone know what that little box is on the back of the new fan shroud? Someone mentioned a CPU? Looks like a small electric fan to ol JJ. [/quote]

pics pics!!!! What are we talking about.

KB, find the "Drove an 06 LLY today" thread or something like that. There are pictures there. I'll try to copy/paste them over here.

On edit, our work computers won't allow me to do this. Sorry. JJ

KB
It is the hill just before Flagstaff coming from Phoenix, heading to the Coral Pink Sand dunes in Utah.
JJ
I Have a front mount hitch which I mounted the dam to. The hitch acts as a nice block going up. As for all the other openings, I did nothing with them other then fasten the lower front flap the the bumper to prevent it from moving. I do think the dam is very solid, a total of 6 1/4" bolts hold it on. 4 in the center area and 1 on each outer end.
Dan

So you didn't block the area between the dam and radiator bulkhead. Hmmmm.

Dam sounds rock solid dwrat! IMHO best to close off as many holes around the stack (tranny lines, flap, etc.) as possible, it will increase +p and help to minimize -p under the hood. Any other mods other than what is in your sig? No programmers, AFE...?

I like the sound of that climb. Good test bed! Lake Powell, breathtaking! I wanna go! lol JJ

KB, did you check out those 06 pictures? That little box on the fan shroud sure looks like it has fins behind it. Hmmmm? No 06's in J'ville to go crawl under on my lunch break. Sure would like to put a bead on one. JJ

My dam is done and I will test it out on a small load Saturday just to see if the fan does not come on all the time is it has in the past on the very same run to the Colardo river. The real test will be Thursday the 28th a 6% hill for 17 miles heading to Utah from Phx pulling 10,000 + toy hauler.http://img311.imageshack.us/img311/4348/cxx3ph.th.jpg (http://img311.imageshack.us/my.php?image=cxx3ph.jpg)

I just finished blocking the holes (incoming cooling air leaks) between my bumper and the cardboard / plastic deflector underneath the stack. I used the aluminized foil stuff for durability but not for looks. I dropped my (stock) dam and wedged the deflector between the dam and the bumper. Had to cut some clearance holes for the plastic nut thingies, it was easiest to just make triangular cuts to miss the nuts. But you can't depend on those gadgets to keep the deflector in place. Hence at least half of the foil used.

Testing next week..

For the record, I like fingers' dam.

Ed

can't find it JJ, help?

can't find it JJ, help?

Dunno if this link will work, but here it is:

http://www.dieselplace.com/forum/showthread.php?t=38434

Joseph

perfect

Are all the hoods the same? I just traided my 2004.5 lly 2500HD in on a 2005 3500 DRW. As I was driving it home I noticed something was really different and it took me a while to figure it out, I know, I am slow :)

The hood on the 2005 is at least 2 and maybe 2.5 inches higher that my 2004. Where I noticed the changes the most is near the windshield. There is a 2.5 inch rise and a small "wall" under the back edge of the hood. The windshield wipers sit in the new "canyon"... My 2004's hood was flush there...

Just checked the build date on the truck 06/05 The truck was at the dealer for 1 day before I snagged it :b
Steve

Is V3.0 the final?

Minor fitup changes need to be rolled back into the design. Maybe one more rev on the rubber and another rev or two on the mounting hardware . This is the first time my buddy has cut rubber. We have some learning curve to climb to refine the cutting process. Shop smelled like someone had been doing burnouts all night. :)

DP? Is that different than Static Pressure? Let's define these terms.

Differential Pressure. Probe in front of the stack and one between the stack and fan inside the shroud.


ok, "fingers special". at some point, if they are removeable, we need to see what they did, if anything, to fingers P drop. I didn't see them before. We know a lot is happening in the fender area. That enhancement resembles my flares on the LT. I don't think all trucks come with it. see what I am asking? I'll wait for him to wake up to respond.


Can't say for sure what if anything the flares do. I would suspect they decrease the DP if anything. Tires stick out about 3"-4" without the flares. So if I do take them off, it can't be for long.

The hood on the 2005 is at least 2 and maybe 2.5 inches higher that my 2004. Where I noticed the changes the most is near the windshield. There is a 2.5 inch rise and a small "wall" under the back edge of the hood. The windshield wipers sit in the new "canyon"... My 2004's hood was flush there...

Steve

I saw that too. Return of the old bulbus hood design. I am thinking that would bring up the highest P zone, so that more of the grill area is higher P

CIT, Can you model that ? Maybe use your current model as the bulbus design, and reduce the height of the entire hood 3". Wouldn't that drop and shrink the Hi P zone?

Fingers, not sure, but thought cit referred to dp as dynamic pressure. Same thing?

If you got 3" diff, I'm wowed.

Fingers, before you get final on the design, do you think you can make it easily removeable? I am really anticipating winter issues. Not just too much air, but snow clearance, etc.

GMC compatible?

I saw that too. Return of the old bulbus hood design. Maybe it somehow modifies the flow to get front P a bit higher.

Can you model that Cit?

It hasn't proven to accomplish squat as far as temps, even changing the hood and grill on a 4.5 to a 05 didn't help (cadent I think did this) and the 05's are overheating anyway on top of that.

.

I think it's differential pressure, usually referred to as delta p, but with out greek characters, is shortened to dp.

Ed

Fingers, before you get final on the design, do you think you can make it easily removeable? I am really anticipating winter issues. Not just too much air, but snow clearance, etc.

GMC compatible?

Jees, KB slow down. Fingers doesn't even have it fitted to his Chev yet and you're riding him to check it out on a GMC. I know you're excited, but you're going to have to clench your teeth a little longer..

Ed

KB/Fingers, as far as winter months go won't a winter cover function even better with this mod in place? We're eliminating or greatly reducing cool air from getting around the stack and into the engine compartment. JJ

For the guys who are savvy on real world use of NACA hood vents. I may want to look at that soon depending on what comes out of the hood mapping.

1.) no water infiltration a must
2.) good venturi action will assist P drop at the highest speeds, where we need it most

I need sources on good quality, field proven designs. Any help is appreciated, you can PM me if you desire instead.

Bettered,

Not taking any ownership here, or "riding" anyone. he may have thought this through already, if not, my remark was only meant to potentially save him hours of time. He will sell this (I presume) if it works.

JJ, If he get's 3" of drop, you may have to thaw out the radiator up north. Besides the 4x guys may want something like this, that can be removed in the field. Just helping. I'll try to follow my own advice. One thing is certain, it should end ac complaints

KB
It is the hill just before Flagstaff coming from Phoenix, heading to the Coral Pink Sand dunes in Utah.
Dan

DW, I got as far as the pull-off area just before the Stoneman Lake Road turnoff. That was when the 'Coolant Hot' indication came on my DIC. OAT was 85 and I had been running 65+ (Predator Tow Tune) from the Sedona exit on up with a 10-12k Toyhauler (see sig). So if conditions are similar, and you get past that point, your doing pretty good. IIRC you still have 5-7 miles past Stoneman before you top out on the rim.

Another good test will be coming back from UT, on the climb up from Cameron to Flag. That last hill is a high, long, steep bee-ach. If your going through Page, there are a couple of more good hot, high altitude climbs as well. (As you probably know)

Good luck!

Time of day will play a part, 3pm the worst.

Bettered,

Not taking any ownership here, or "riding" anyone. he may have thought this through already, if not, my remark was only meant to potentially save him hours of time. He will sell this (I presume) if it works.

JJ, If he get's 3" of drop, you may have to thaw out the radiator up north. Besides the 4x guys may want something like this, that can be removed in the field. Just helping. I'll try to follow my own advice. One thing is certain, it should end ac complaints

OK sorry, I thought I'd seen at least two requests on him to make it GMC compatible, and an answer that you (or someone) was to deliver the truck to him for fitup / checkout.

On the sales deal though, you are quite correct. If this works he's going to have a hotcake machine. For all we know, GM will be buying them. An additional advantage I've observed - the cast tab on the bottom of my rear end will no longer be the low point on my truck!!


Ed

FWIW, the dam material is very durable and will flex below the frame attachment points. No need to remove it. I may put a couple of holes along the lower edge to you can tie it up.

No plans to sell unless it does some good. Off to drag a trailer up a few hills.......

Go Fingers, Go Fingers, Go Fingers .... Anxiously awaiting your test results.

Anyone laid their hands on a 06 yet? JJ

JJ...I tried finding that post. I could've sworn it was by a new member named "Performance". It's not in New vehicle info any more.....if it was moved, I have no idea where it went.

But I did find this one.....with pictures....http://dieselplace.com/forum/showthread.php?t=38434&highlight=dealer+2006

Yeah...give Fingers time. Can't tell he loves Dmaxs, can you?

ON EDIT.....see the link posted by Colnago about 6 down from this...thats the thread I was talking about.

For the guys who are savvy on real world use of NACA hood vents. I may want to look at that soon depending on what comes out of the hood mapping.

1.) no water infiltration a must
2.) good venturi action will assist P drop at the highest speeds, where we need it most

I need sources on good quality, field proven designs. Any help is appreciated, you can PM me if you desire instead.

Stock Car Products and Coleman Racing are a good source for those ducts. Water intrusion is going to be hard to prevent unless you duct the ducts (is that even right??) down to an area that will allow them to drain water directly to the ground, but still pick up the high pressure air.

Is there anything out there that is designed for street use, and pulls well with speed (venturi design)?

Not a hot day here. In the low 80's, scattered showers.

Excavator on the trailer. Trailer 7,500 lbs, machine 12,000, and truck. cross the scales a little over 26,000. ;)

Hills were ballbuster (Dravosburg hill for any locals), Library hill, and South Park hill.

Finally found out what the fan pulls when fully engaged. 3.5 inches of water. That's a lot of suck.

Today I rarely got over 40 MPH. At these low speeds the dam is nearly useless, and you gessed it. No Joy. Got hot in all the usual places. Temps up to 244 or more. The onset was delayed, but the result was the same. There may be better results at highway speeds, but I have not tested that.

Personally, I am gonna keep the dam installed. Cool downs seemed faster and I like the look. But I will not be selling them.

Fingers, what are your thoughts now? At speeds under 40, and that fan sucking that well, seems to me that the radiator is not large or efficient enough...

Or is the stack too restrictive as far as airflow is concerned?

Fingers, what are your thoughts now? At speeds under 40, and that fan sucking that well, seems to me that the radiator is not large or efficient enough...

Or is the stack too restrictive as far as airflow is concerned?

Before I go chasing my tail any more I need to get the coolant temps going in and out of the engine.

I see it going one of two ways. Either a bigger radiator, or flow enhancements for the engine.

So since the '06's are trickling in to the dealers, should we now be able to query the Parts Dept. to see if the radiator #'s have changed?

Fingers: If it isn't head casting issues or blocked passages the only other thing I can think of is the bypass port being too open and choking off your flow to the radiator, or at least reducing it enough to reduce cooling with the water doing big circle mostly in the engine.

You willing to pull out the rear stat and put a fixed orfice in there for a test? You have to leave a little flow for the coolant and to prevent cavitation. Seems someone like you could test this easily.

.

Shields up.

.

Fingers, did you do a pressure measurement? This is tricky business. We have never established what the rear P measurement is (no fan).

an undertray is what I originally had in mind.

Learned quite a bit lately about nose angle, and its importance, raise the back or lower the front can help evacuate more air.

The stat housing is o-ringed, easy for you to open that bad boy up and have a look-see on what I mean.....

.

wake me when it's over.

Fingers:

The 3.5 inH2O...between which two areas was it measured?

Fingers, did you do a pressure measurement? This is tricky business. We have never established what the rear P measurement is (no fan).

an undertray is what I originally had in mind.

Learned quite a bit lately about nose angle, and its importance, raise the back or lower the front can help evacuate more air.
KB- enlighten me- Is the tail drag when loaded hurting or helping? I know my dually will drop about 3" with the RV, my 2500 has bags and depending on what I have psi wise in them I can take the drop out (just rougher ride), Is this a major thing or just one more of the several small things add up to the OH and -:t coolant?

Just an FYI for those interested, someone posted some additional photos of the '06 engine compartment in the Allison OEM forum:

http://www.dieselplace.com/forum/showthread.php?t=38431

Joseph

Oh man, the mirrors, they are listening!
That fan, looks like a major change.

Fingers: If it isn't head casting issues or blocked passages the only other thing I can think of is the bypass port being too open and choking off your flow to the radiator, or at least reducing it enough to reduce cooling with the water doing big circle mostly in the engine.

You willing to pull out the rear stat and put a fixed orfice in there for a test? You have to leave a little flow for the coolant and to prevent cavitation. Seems someone like you could test this easily.

.

Shields up.

.

There are a number of things it could be. Pump stalling, head passages, return line, thermostats.........and the list goes on. I am not going to do anything till I get some hard numbers on the coolant temp change across the engine. I would love to get flow numbers too, but that one is harder. The dam wasn't a total failure. But it is not the answer either.

The latency with which the overheat comes on has bothered me for a while. It takes too long. I have always attributed that to the being just barely under cooled. But I was wondering if the oil and its cooler are in play here somehow. I know one of the changes with the LLY was improved oil cooling of the pistons.........

KB- enlighten me- Is the tail drag when loaded hurting or helping? I know my dually will drop about 3" with the RV, my 2500 has bags and depending on what I have psi wise in them I can take the drop out (just rougher ride), Is this a major thing or just one more of the several small things add up to the OH and -:t coolant?

that's about 2000 lbs then, aay?

Tail up is better. If your t-bars are cranked, it is better to lower them. The idea is to provide a larger undercarriage evacuation area (rear) than the front entry area (under bumper). A vacuum is created. It's on my list of things to verify.

My guess it is very minimal in effectiveness.

Is the rougher ride when higher, because you are slapping the overloads or the slappers? That can be remedied by flipping the overloads, but I wouldn't recommend that to you, you sound heavy. The airbags increase overall spring rate, but slapping the overloads is like instantly doubling it, no progressiveness.

Fingers, did you do a pressure measurement? This is tricky business. We have never established what the rear P measurement is (no fan).

an undertray is what I originally had in mind.

Learned quite a bit lately about nose angle, and its importance, raise the back or lower the front can help evacuate more air.

All of my measurements are relative front of stack to back. I do not have instruments that allow me to reference absolute pressures. So I can't give you that number. The cab is not a good reference point. I was only interested in improving stack flow.

Fingers:

The 3.5 inH2O...between which two areas was it measured?

Differential pressure between the front and rear of the stack.

Just an FYI for those interested, someone posted some additional photos of the '06 engine compartment in the Allison OEM forum:

http://www.dieselplace.com/forum/showthread.php?t=38431

Joseph

Wow! I wonder if thats true cold air intake?? Looks impressive!

Fingers, did you catch my bypass post?

.

that's about 2000 lbs then, aay?
Close to 3200, depending on how Its loaded, empty toy box or 4 quads.

Tail up is better. If your t-bars are cranked, it is better to lower them. The idea is to provide a larger undercarriage evacuation area (rear) than the front entry area (under bumper). A vacuum is created. It's on my list of things to verify.
Stock tire/ factory t-bar settings.

My guess it is very minimal in effectiveness.

Is the rougher ride when higher, because you are slapping the overloads or the slappers? That can be remedied by flipping the overloads, but I wouldn't recommend that to you, you sound heavy. The airbags increase overall spring rate, but slapping the overloads is like instantly doubling it, no progressiveness.
Heavy, thats why I bought the dually, the 2500 towed fine but I was way over on the pin weight.

Air bags on the 2500 because of the weight and the v-bas salter I run in the winter.

We do know that high load conditions cause an oil pressure drop, which is most likely high oil temperatures.

Perhaps a better oil cooling system might be advantageous. Do they make an external oil-cooling system for the Dmax?

Fingers,

I have a special favor to ask if you go back out. If you have something to monitor IAT, please do. I think you could be shortchanging yourself. Is it possible the latency you speak of is the IAT induced HP loss? That takes a while to develop.

Yes I saw the post. I am not going to do anything till I can quantify the results somehow.

IATs were fine (12* over ambient) till the fan kicked in.

Tail up is better. If your t-bars are cranked, it is better to lower them. The idea is to provide a larger undercarriage evacuation area (rear) than the front entry area (under bumper). A vacuum is created. It's on my list of things to verify.

KB,

Does this mean that we can create a vacuum by raising our beds 1" - 2" off the frame? Would this create enough of a vacuum to pull more air through the radiator/engine compartment, thus helping the OH issue? Or did I completely miss the point of your post?

Just wondering out loud,

Joseph

The latency with which the overheat comes on has bothered me for a while. It takes too long. I have always attributed that to the being just barely under cooled. But I was wondering if the oil and its cooler are in play here somehow. I know one of the changes with the LLY was improved oil cooling of the pistons.........

I did not realize until I went to the Dmax engine site yesterday, that there was an oil to water cooler ahead of the filter. With EGTs >1,300, the piston cooling you speak of and a turbo dumping hot oil, makes me wonder too. Reminds me of my '65 Corvair Corsa Turbo. Once the oil temps got to a certain point, forget about it...

Any idea where in the cooling stream that oil cooler is? i.e. is it first or last?

I did not realize until I went to the Dmax engine site yesterday, that there was an oil to water cooler ahead of the filter. With EGTs >1,300, the piston cooling you speak of and a turbo dumping hot oil, makes me wonder too. Reminds me of my '65 Corvair Corsa Turbo. Once the oil temps got to a certain point, forget about it...

Any idea where in the cooling stream that oil cooler is? i.e. is it first or last?

Water goes straight from the pump to the oil cooler then to the rest of the motor.