Well i have an 05 LLY bone stock and am the original owner and i can tell you that it was an over-heater to say the least! And if it was not over heating the fan was locked up at %0-100% 80% of the time which killed my fuel mileage. The fix from Chevy did nothing whatsoever. I never limped it cause i always gave it a rest pulling grades. The 395 outside of Bishop Ca. was always a bear to pull. Sold the Lance and am looking at TTs. knowing i would be pulling more weight than hauling i fixed my over heating issue by installing an auxiliary radiator with an electric fan! After A LOT of research i only found 100% success stories with this set up. My fan never runs and i just hauled three yards of pea gravel in 78 degree temps and i could not get the temp above 198 and i drove it hard! Before the aux radiator my trucks fan would of ran and cycled constantly. What i am saying is if you find a LLY dont be afraid of it. The LLY and LBZ were probably the best years of the Duramax emissions wise.
2005 2500HD D/A
2006 Lance MAX 881 Loaded, Supersprings, Air Lift air bags, Vision type 81 wheels, Dunlop Sp-431 245/70/19.5 load range "H"
I had an 04 with an LLY duramax. I towed many thousand miles with it and when it had 144000 miles, I sold it to my son-in-law. It now had 190000 miles on it and still going strong.
When towing up Afton mountain in VA, a 6-7 percent 6 mile upgrade, it would go up to 230 or so about halfway up and when the fan would lock up, the temp went right back to normal and would stay that way. I don't consider that bad for towing a 13500 lb 5th wheel. Never used andy oil or coolant and still doesn't.
Well i have an 05 LLY bone stock and am the original owner and i can tell you that it was an over-heater to say the least! And if it was not over heating the fan was locked up at %0-100% 80% of the time which killed my fuel mileage.
Sounds like ours, temps over 80 on mostly flat ground will have the fan HOWLING. And that was with the mid profile Jayco, the Mountaineer will be worse.