Join Date: Sep 1999
Location: Philadelphia, Pa.
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Re: my heater is always blowing hot air!
Another thing to check is the operation of the vacuum operated valve in the heater hose in the engine compartment. This valve is normally closed, meaning it needs vacuum to open. When the engine is running and the cabin control is not calling for heating, vacuum closes the valve, stopping flow thru the heater core. When the engine is shut down, the lack of vacuum allows the valve to open therby allowing coolant to flow bypassing the closed engine thermostat. This allows the pressures to equalize and prevents an air bound system. If the valve fails in the open position, you would get hot coolant through the core at all times. Good Luck!![img]/wwwthreads_images/icons/smile.gif[/img]