Having a strange problem that I have not encountered; and this being one of the few cruiser bb with some diesel experts.... I have a 1985 FJ60 with a Cummins 6A3.4t. I am running a stock radiator, cleaned out, new Napa-brand 13 lb cap. The engine has dual thermostats, relatively new. The problem is the lower radiator hose keeps trying to blow off. No matter how tight I make the clamp. I assumed it was because the lower outlet of the radiator didn't have a "lip" on it. I had a shop put one on, and that solved the problem for a while. Then it did it again. I've never dealt with a dual thermostat system... seems overly complicated to me. Could a bad thermostat cause a hose to blow off?! What about a bad radiator cap? I would think that if the headgasket was blown (unlikely, it has not been overheated; no oil in the water, no water in the oil), it would first blow the cap (13 lbs)... but I'm not getting a large amount of fluid in the overfill. Maybe the new cap (again, Napa brand) is bad?