dat dood
+1y
Does the problem persist after removing the t-stat? If so, you're pressurizing the coolant system by some means. If not, you're still getting trash in the t-stat causing it to stick. Also, radiator could be partially clogged causing a bottle-neck and resulting in build up of pressure at feed hose. Isolate, isolate, isolate. If the radiator is full and you pull the hoses it should be empty in just a few secs. The feed hose from the engine should also move A LOT of water while the engine is running. Also, change your radiator cap, it should vent pressure at a certain psi. If it's not it could cause pressure to build.
Just because you're not mixing oil and water doesn't mean the head gasket is good/properly torqued.
Samurai's are notorious for the gasket blowing between #3 and #4 cylinders causing tons of blow by and smoke.
My B2200 that I'm driving now has a bad head gasket, it's causing me to loose about a quart of oil per oil change. It leaks out just below the #4 exhaust port. No smoke, no oil/water mixing, just a leak where the oil return at the back of the head is.