Chevy Silverado
Heater Cores and Blower Fans
Car Heaters

Why would a 1989 Chevy Silverado 350 heater only put out luke warm air even after changing the thermostat and back flushing the heater core?


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Wiki User
2009-02-06 04:16:24
2009-02-06 04:16:24

I had the same problem. The answer to your problem is simple. You have an air pocket in your cooling system. Simple fix - take the radiator cap off of the radiator, turn the vehicle on and let it run for 1hr to remove the air from the system. Also, make sure your overflow container is atleast at the minimum level. Answer If your certain you have all of the air out of the cooling system the blend door inside the heater box may be stuck open.


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The heater might blow cold air in a 2000 Silverado because the thermostat is sticking and not changing from cold to heat. The thermostat is usually located in a hose that leads from the radiator to the motor.

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Before CHanging the Heater Core, have you tried flushing it? I have a 99' Jimmy and have to do this every year to get my heater to work.

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