[John Poling]

Let's keep in mind that Roscoe said he had been driving his car for a year with no issues as far as overheating and then it started to heat up. All of the testing and experiments he has done discounts pretty much any possible engine mechanical problems.

Roscoe, a few posts back Jack21 suggested the lower radiator hose being a possible culprit. I would look here BEFORE removing any more engine parts. I don't believe that I saw anything in this string suggesting that you have replaced it. My suggestion would be to fabricate as much of the lower hose out of hard (steel or aluminum) tubing as you possibly can. The lower radiator hose in a normal x-flow radiator is under a "vacuum" of sorts when the engine is running and under a more extreme "vacuum" at off idle conditions. As your componants age so does the rubber on your hoses which weakens them in the process causing the hose to partially collapse if not fully collapse if it does not have an internal spring coil for support. Even if you have the spring there, it doesn't mean that it is doing what it is supposed to. In my 20 or so years of playing with cars, I have run into this more than once, of course after I had gone through everything like what you have been.

Again, PLEASE try this before tearing into your engine deeper and eliminate this possibilty.

John