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Duramax Second Generation: 2004.5-2005 (LLY) Discuss the second generation (2004.5-2005 LLY) of the 6.6L Duramax diesel engine & associated components. 2006 LLY engine discussion belongs in Third Generation forum due to the differences of the 2006 LLY and the 2004.5-2005 LLY. Engine related discussion ONLY.

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Old 07-18-2005, 02:07 PM   #1 (permalink)
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OVERHEAT Solutions

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.

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Old 07-18-2005, 02:34 PM   #2 (permalink)
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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.

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Old 07-18-2005, 02:59 PM   #3 (permalink)
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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!
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Old 07-18-2005, 03:00 PM   #4 (permalink)
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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...
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Old 07-18-2005, 03:18 PM   #5 (permalink)
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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.
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Old 07-18-2005, 03:40 PM   #6 (permalink)
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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.
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Old 07-18-2005, 03:54 PM   #7 (permalink)
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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....

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Old 07-18-2005, 04:14 PM   #8 (permalink)
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Much has been looked into. I came into this topic on post 1272 here. 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.
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Old 07-18-2005, 04:59 PM   #9 (permalink)
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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.
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Old 07-18-2005, 05:03 PM   #10 (permalink)
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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.

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