LLY Overheaters?

[killerbee]

so this has to do with how the heat of the engine circulates with the radiator? what about the cooling fan that is supplied from the factory one would think that the fan would be sufficient. I am still relatively unclear about how you can overheat your engine when you first have a diesel which can tolerate heavy towing weight and i am sure the factory and engineers realized that with this diesel engine certain things would need to be compensated. I thought the maximum towing weight for a 2500hd, which is what i have, is 12000lbs not gross weight mind you, just plain weight. aerodynamics of a trailer you pull should have little to no impact on the engine, its the weight your pulling and environmental factors, ie heat outside and incline of road. also running a large tune and going 85 with a large load will make the engine work harder and a lot of guys do that and complain about engine problems. i am not trying to start a war but i am trying to rationalize this issue and understand it. I want to tow my toys with my truck and i know it can do the job but i also know its limits and when to stay in those limits. jmho though let me know what you guys think

Sorry, missed your question 6 months ago. I just came back to ask for a smaller rendition of the Allison removal guide and found this thread again. So FWIW:

LLY heat issues have nothing at all to do with the cooling system failing to do it's job. In fact, any cooling system would overheat, given the factory configuration. The Induction system is what overheats these trucks. It is a destructive loop called Thermal Feedback, a term to describe a mechanism that creates a CAC that is so hot that anything sitting behind it (like a radiator) has no chance of being efficient at cooling.

If you don't mind reading, here is all my findings, from simple to serious. It describes how the loss of the wastegate, and some undersized plumbing, made an issue for the LLY. All LLY from 04.5-05, all have exactly the same problem, so please don't cast it aside because "my LLY does not overheat". Glad it doesn't, but you (all) still have this problem. Whether you do something about it is another matter.


Definition:
http://members.cox.net/td-eoc/THERMAL FEEDBACK-SIMPLE.pdf

Easy to understand:
http://members.cox.net/td-eoc/LLY Induction Overheating.pdf

Involved Proof:
http://members.cox.net/td-eoc/INDUCTION-THERMAL FEEDBACK PRIMER.pdf

Interesting Calculator:
http://members.cox.net/beekiller/GMC Light Duty/Turbo Calc spreadsheet.xls

FAQ's:
http://members.cox.net/beekiller/GMC Light Duty/INDUCTION OVERHAUL FAQ.doc

 

[fastgreek]

never had an issue with mine

 

[Tugs]

Now, I know that I do not tow on the grades that others that live out west do but I have never (at least not yet) had a problem.

I just came back form towing a 8.5x26 foot car hauler down I-95 from Pennsylvaina to Florida. I weighted my truck and trailer on a Cat Scale and the total weight was 19,860 pounds. When I got down south the temps where in the high 80's to 90's. What it would have done with larger grades I do not know but it did fine and my trans temp ran around 180.

With the trans in T/H I was able to keep it at 68 mph with the cruise control set. Hand calculated, I averaged 9.5 for the whole trip.

 

[bigdisneydaddy]

My first travel trailer was a flat front 6400# 27ft
second one is a seriously slanted front a little over 9000# and 32 ft body
both well within the 12,000# rating on the truck.

When I first got it the truck would have fan engagement on flat ground at 65 MPH towing the smaller trailer and the temp would climb to 230 with any short grade (Zillwaukee bridge for those familiar with I75 in MI)

I did the following things to improve it (notice I didnt say "fix")
cold air duct kit from TxChristopher
water wetter in the coolant
4" magnaflow exhaust without cat
new intake elbow (GM stock for LBZ)
Hypertech power programmer set on 3

For me, these things almost completely made the fan not need to engage. The only time it would come on is over 80degrees at the end of a ramp while slowing down, at the end of a long stretch.

Having said all that, I had read from members out West that the true test of any improvements is in the grades in the West. I found this to be absolutely true during a recent trip. The higher elevations and the longer grades were apparently the test. While it wasnt too bad on I25 from Denver up into Wyoming, it was noticeably harder for the truck to stay at 200 engine temp.
I did take the programmer completely out of the truck and reinstalled the stock tune while in CO. mostly due to the fact we were just driving around not pulling the trailer and it helped with the smoke.
The real test came as we left Yellowstone and headed into Bozeman and then East on I80. The truck struggled on several grades and was well into the 230 range on the dumbed down, inaccurate gauge. As the temps rose into the upper 80's that day the fan was on almost all the time. Although I didnt hit any alarms my mileage was horrible at about 8mpg while only going 60-65MPH. I put the tuner back in the truck on the second morning when we stopped in SD but by then it had flattened out and the elevation was much lower, it became a non issue again.

Long story short is that if I lived in the West the truck would be intolerable to me, a V2 would be in the budget right away.

Scott