Been reading this post with interest, as i have been having overheating problems with my truck, pulling my trailer. On level streets or highways, no problem, soon as i hit a hill, as on PA turnpike going to Maple Grove, i can watch the temp climb rapidly. Got me thinking, and saturday nite, i started my truck, let it warm up and checked the flapper, inside the snorkle extension of the air cleaner. It was completely closed, wouldnt open up, so i flipped over the top lid. Air cleaner was new, and the truck stopped shaking and ran smoother. I wont know if this will cure my heating problem, until the spring, but, i was desperate. Everything that was mentioned here, i've done, radiator, hoses, waterpump, spring in lower hose, distributor, fan clutch, you name i've done it. I would think the motor would go super rich, with this problem, and computer is trying to compensate. Again, i won't know until spring. Dave ss/ea 1355