Heating Problem

I am not getting heat. Fan blower works- Heating control valve “new” works but no fluid is going into core. Had engine and core flushed-told core was fine-no blockage. Thermostat “new”. When I turn on the fan the " Heating Control Valve diaphragm appears to be working. The engine is getting hot and over heating than temperature goes goes down-could this indicate water pump blade is broke not pushing throw fluids? I am at a real loss here! Help cold weather-freezing weather coming.

There may be air trapped in the cooling system.

To purge the cooling system of any air, get the engine up to operating temperature. With the engine idling, slightly loosen the upper radiator hose clamp. Take a small flat bladed screwdriver and slip this between the upper radiator hose and the radiator hose neck. Allow the engine to continue to idle until the spitting and sputtering at the radiator hose stops and all that comes out is coolant. Remove the screwdriver, and retighten the hose clamp.