OK, I cleaned everything and had a look at the whole heater system. I need some help with the heater control valve.
I think there is the problem.
If i turn on the heating and put on hot, there is no Underpressure from the hose. If i put on cold, there is underpressure constantly.
OK, if the Membran of the heater control valve doesn't have underpressure, the valve is closed. But if the valve is closed, the hot water can't run through the hose. so it should be the opposite. But the Valve seems to be OK.
I heard that there are exisiting valves from G.M. that look totally eqaul, but one Valve is open without underpressure and the other one is closed.
Is that right? That might be my Problem, doesn't it? It's just strange. thans for your help.
Engine Code Y, Oldsmobile 307, Model 1990
have a look at the picture, thats how my valve looks:
regards