I took the heater core hose that comes from the water pump (thru the metal pipe under exhaust manifold) loose at the firewall. There was no water coming from the pump. I also took loose the small hose at the thermostat that comes from the water pump as it was easiest to get to. I was able to blow back from the heater end and have water come out at the thermostat end of the hose. The top radiator hose gets warm and the gauge runs mid scale when the engine is warm. Just drove it
180 miles yesterday no overheating problems. Why can I blow back thru the pump but no water will flow to the heater?
BTW, I did have to have head gaskets replaced recently but heater problem was the same before and after. But the shop said there is no such thing as a weak water pump, it either works or it doesn't.