Hi SpelantI've replaced the t-stat once but I am beginning to think that it might be the culprit. I'll do the hot-water trick to see if it operates. Perhaps time for a new one anyways since it has been a few years since I replaced it and over the past few years the cruiser has sat more than ran.
Oil cooler.By the way, where do those two black coolant lines to the left of the t-stat housing go? Mine have been blocked off since I purchased the cruiser in 1989.