more investigation shows valve idea wrong. the heater control valve is vacuum activated. I did find that if I accelerate the engine temp drops and the heater puts out heat. new idea is I have a faulty heater control valve and when the vacuum drops it allowes the hot water into the heater core which acts as a secondary radiator, cooling the engine. this leads me to believe I have a faulty radiator. I will need to test the valve, vacuum lines and likely replace valve. then have the radator tested.