my set up 350 4 core radiator thermostat housing with cap 2 overflows one up front one in rear just replaced thermo. w/ a 160 now it doesnt overheat but it pressurises and starts filling rear overflow till it eventually starts leaking and the thermostat hose is rock hard when i shut engine down eventual it sucks the coolant back into the system from rear overflow. when i changed thermostat there was quite a bit of green calcium build up any ideas??
One of the two caps needs to be a pressure release cap, otherwise thermal expansion of the coolant will start breaking parts. Calcium is white, the green is antifreeze, you probably have highly mineralized water where you're at so you should use distilled water from the store. Filtered water isn't the same as distilled water.