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Open Roads Forum  >  Tow Vehicles

 > Why does my 05 GM duramax get so hot?

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turbomist

Clovis, NM

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Posted: 07/18/07 08:42am Link  |  Print  |  Notify Moderator

I have read a few things and see what some consider to be a solution to summer overheating, and that's not my question. Does anyone have an answer to what the cause of this is?

bstock

Las Vegas, Nv

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Posted: 07/18/07 08:45am Link  |  Print  |  Notify Moderator

go to dieselplace and search overheating there is a ton of info. there are alot of knowledgable people on that forum regarding our trucks. they have helped troubleshoot my truck when the dealer couldnt figure it out.
bj


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crashpilot

Green River, WY

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Posted: 07/18/07 09:03am Link  |  Print  |  Notify Moderator

The LLY overheaters are the subject of much debate. There is no doubt that some guys are truly having troubles with thier LLY staying cool, some guys like me have no problems. You're right it is perplexing and the subject of much debate. But I think the answer to your question is that there has not been any authoratative/official explanation as to why these engines are having trouble staying cool. There are a lot of really smart guys who've looked into this, and they all seem to have thier own opinion but there is still no magic "cure all" for the woes of the guys overheating.

Like bstock said, there is more discussion and information at the diesel place than you can sit and sanely read. Great resource for all things D-max.


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FLSTFI Dave

East TN

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Posted: 07/18/07 02:26pm Link  |  Print  |  Notify Moderator

I am one of those guys that had a overheating LLY truck.

A little background, I have had the Same RV for 10 years, and four GM crew cab dually trucks. The first was a 96 big block gasser, the second an 01 LB7 duramax, the third a 05 LLY Duramax and now a LBZ Duramax. The RV is 12,000 pounds.

No truck except the 05 ever got over 220 pulling the RV, on any grade or any outside temperature.

The 05 would hit 250 plus on the coolant, and the transmission. All it took was a long grade with moderate outside temperatures or a short grade with 90 plus outside temperatures.

The cooling system in the 05 was exactly the same as the 01. That is the problem, the 05 produced much more heat due to more power and much more pollution controles. The cooling system can not disapate the heat the engine generates, especially under a heavy load with high wind resistance on a grade on a hot day.

GM has not come up with a fix yet, they have several band aids but none solve the problem for the heavy haullers on a long mountain grade with high outside temperatures.

Mine left me on the side of I-26 Saluda grade in NC puking coolant. GM eventually bought it back.

Their is a fix, but it by a private person. He is on the diesel place web site. He makes an V-2 modification that has stopped the overheating on many trucks. He also has a web site cool my duramax.

I have personally driven an 04.5 that puked it's coolant and my 05.


2006 GMC SLT 3500 Crew Cab Dually 4x4, Duramax/Allison, Loaded
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turbomist

Clovis, NM

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Posted: 07/19/07 08:11am Link  |  Print  |  Notify Moderator

Thanks for the replies. I had already seen the dieslplace. It is a real headache, and there is no answer to my question to the cause. I am really not impressed, so many experts and no real explanation, just egotism and randomness from what I can see. But before I try to do something about it, I want to know as much as I can.

FLSTFI Dave wrote:

the 05 produced much more heat due to more power and much more pollution controles. The cooling system can not disapate the heat the engine generates,


Is this speculation, or do you have some data that can back this up? I hope I am not asking too much or offending. It appears that polution controls do not explain it since everyone disconnects them. I don't see more power in the vehicle. So I hope you don't mind my devils advocate.

FLSTFI Dave

East TN

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Posted: 07/19/07 02:43pm Link  |  Print  |  Notify Moderator

turbomist wrote:

Thanks for the replies. I had already seen the dieslplace. It is a real headache, and there is no answer to my question to the cause. I am really not impressed, so many experts and no real explanation, just egotism and randomness from what I can see. But before I try to do something about it, I want to know as much as I can.

FLSTFI Dave wrote:

the 05 produced much more heat due to more power and much more pollution controles. The cooling system can not disapate the heat the engine generates,


Is this speculation, or do you have some data that can back this up? I hope I am not asking too much or offending. It appears that polution controls do not explain it since everyone disconnects them. I don't see more power in the vehicle. So I hope you don't mind my devils advocate.


TX Christopher ( on the diesel place or cool my duramax)is the one who can best answer all the questions. GM at arbitration is who told me the cooling system is inadiquate to meet the new emissions requirment. The Turbo was change for this as was the compression and piston design along with several other internal changes to make the LB7 a LLY. So it is not just the EGR, and Cat. It is also intake timing, valve timing and so on.

That was one of my biggest compalints about my LLY. GM advertised it as more HP and More Torque than the LB7 is replaced. Yet it never felt as strong as my LB7. On a dyno it did put more torque to the rears than the LB7, unitl the lly got hot, then it was way down on torque.

Also check out the major changes made to the 06 LBZ cooling system compaired to the 05 and earlier cooling system. All was done to address the heat issues. Even the engine air was taken from out side the truck now, to again limit heat.

TX's V-2 mod does cure the problem.

rob85546

Hot arizona

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Posted: 07/19/07 05:46pm Link  |  Print  |  Notify Moderator

I would 2nd dieselplace.com... The LLY are known for that.... But Kind of like the Ford 6.0psd deal, alot claim no probolems... I have seen on dieselplace there are some things you can do to help it.. I would keep pestering the dealer since its under warranty. Or get you the LBZ D-max......


bstock wrote:

go to dieselplace and search overheating there is a ton of info. there are alot of knowledgable people on that forum regarding our trucks. they have helped troubleshoot my truck when the dealer couldnt figure it out.
bj


killerbee

PHOENIX USA, Never hot

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Posted: 07/20/07 11:14am Link  |  Print  |  Notify Moderator

turbomist wrote:

Does anyone have an answer to what the cause of this is?


How much do you want to know? Motor heat production is not a factor in this. It didn't change. The new EPA requirements had no real hand in it either.

The bulk of the explanation you seek, is in the redesign of the forced induction system. The only question, is how much do you want to know? The technical explanation is confusing to some.

Any cooling system expansion, is a mask. It does not address the causal mechanism at the origin, and therefore the term "band-aid" loosely applies.

If you want a headache, read the dieselplace, but you won't find the answer you seek, it's not there. But you will get real good at selling used vacuum cleaners.


Michael, Systems Engineer and Professional DURAMAX Diesel Tuner
Killerbee Performance


turbomist

Clovis, NM

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Posted: 07/20/07 03:32pm Link  |  Print  |  Notify Moderator

I want it all. I am a civil engineer so you wont lose me. Are you saying that the radiator capacity is enough? If so, how can it overheat? The forced induction system? How can that possibly be to blame? I'm not doubting you. Please don't take exception. I do some playing around with gas motors, so I am no stranger to car talk.

I agree with your last statement. I have read for hours and Crashpilot is correct. There is no definitive conclusion with evidence. It is really weird, when someone tries to form an argument, that Txchristopher freak just puts a megaphone in his ear and blows him out of the conversation. It is just a mishmosh of opinions and a&&holes so I hope you have better carma. I am tired of doublespeak and being talked down to.

killerbee

PHOENIX USA, Never hot

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Posted: 07/21/07 10:06am Link  |  Print  |  Notify Moderator

OK, the straight dope.

This became a project for me about 3 years ago when the LLY was released. It was definitely a slow learning process. The issue is so elusive; I had to dissect every mechanism in the vehicle to finally track it down. For me the heat transfer mechanisms were easy to log, easy to track and easy to assemble. The thermodynamic mechanisms, and what would turn out to be hidden flaws, were much more difficult to nail down. I had to relearn compression thermodynamics to finally arrive with my finger on the cause.

So I’ll start with the statement, then I can explain the rationale. For the most part, the changes that brought about LLY overheating, for those that utilize the vehicle in severe work conditions, are 1) the elimination of the wastegate, through adoption of the variable geometry turbocharger, and 2) the reduction in size of the induction plumbing…CAC boost tubes. It is also important to note 3) the fan coupled IAT rise. This is not a change for the LLY, but it is a critical element.


1. Wastegate. By and large, the wastegate has multiple functions. For this discussion, the applicable feature of the wastegate is its inherent ability to put a hard ceiling on the work performed by the compressor. Most people just recognize that it limits boost, bypassing exhaust flow when the preset compressor boost limit is reached. That boost is sensed at the compressor discharge where the wastegate line is located. But also, in a real thermodynamic sense, it limits the heat that the compressor can generate. I guess I will skip compression thermodynamics, accept to state that the turbo creates a lot of heat in the charge air (measured up to 590 F). If IAT goes up, then this heat also goes up. The magic of the wastegate is that as IAT gets hotter, the compressor is moderated to keep from further heating the charge air. The reason this is, is that the wastegate controller maintains a hard boost limit on the discharge, and this equates to a quasi-hard limit on heat production.

The VGT cannot do this. It has no boost or heat limit protection, no wastegate, nor even a PCM code to detect this issue. When IAT heats up and begins to heat charge, there is NO MECHANISM to limit work (and heat) produced by the compressor. Where the LB7 boost is controlled to a discharge limit, the LLY is controlled to the intake plenum requirements of the MAP sensor. It asks for 20 psi, and if there is 400 mph air charge due to heating and a 7 psi loss in the plumbing, then the discharge is commanded to 27 psi. It’s that simple. With this much discharge boost, the compressor is operating off the map much of the time, especially at higher elevations. This means yet more heat due to the lower operating efficiency of higher boost.

2. Plumbing sizing. This is a critical science by itself, all fluid transport systems must be carefully calculated to minimize losses. When dealing with adiabatic compression, it is ultra important. Restriction means lost boost and added heat. GM botched this one. The LLY emerged with very restrictive boost tubes, undersized for the application. Went from the LB7’s 3” to 2.5”. That increased charge velocity in the pipes 44%, leading to double and triple friction losses, between 2 and 3 psi of boost. An awful waste of boost, and tragically, huge consequences in heat production. So the heat machine (VGT), sends the resultant heat product to the CAC, where with all its added heat load, rejects tons more heat into the ambient stream, firebombing the radiator in effect, with ambient as hot as 240 degrees.

So the radiator has plenty of capacity, when it receives the intended cool air. The problem is what happens in front of the radiator, which leaves no cool air to do do the job of dropping coolant temp.

With EFILive, it is possible to create a software “wastegate”. I have been playing with this concept for awhile.

Anyone can solve the overheat issue by employing a cold air intake (one that works, buyer beware!), with larger boost tubes. I have had very good results with this, I’ll see if I can find the charted data.

Or MASK it with cooling system expansion. But you are still left with all the byproduct of poor induction design. The main ones are power loss, climbing EGT, and reduced turbo life. Without these changes intake temp (post CAC) can get real high, over 250 degrees, and this leads to significant oxygen loss and power loss on the grade, and high EGT. The ONLY way to address that is keeping IAT down at the airbox, and then helping out the efficiency issue further by using the larger boost tubes. Basically create the least restriction possible in the plumbing. When you do this, power is up, and grade speed is up, and this is good for cooling. Because it has to work less, the turbo rpm is reduced by over 10,000 rpm, and this means lower exhaust backpressure, and 100-200 degree lower EGT’s, not to mention a grateful turbocharger that will outlast your neighbors as you are passing him on the grade.

Michael Patton-Enervative Product Engineering

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