Cold air coming when the heat is on.


Cold air coming when the heat is on. Mechanic's Assistant: Have you checked the coolant level? Have you checked for a leak in the radiator? Yes and yes Mechanic's Assistant: What is the make/model/year of your car...

Cold air coming when the heat is on. Mechanic's Assistant: Have you checked the coolant level? Have you checked for a leak in the radiator? Yes and yes Mechanic's Assistant: What is the make/model/year of your car? 2009 GMC Sierra 1500 Mechanic's Assistant: Are you fixing your Sierra 1500 yourself? What have you tried so far? I have replaced the thermostat. At High RPMs the heat works okay, then at lower RPMs it turn cold.

Automotive Expert
Good Afternoon , That sounds like the coolant is low and there is an air pocket .

It is not low. Previous to this happening, it would over heat and then rev up the engine, then it would cool down. I replaced the thermostat. It no longer over heats, but will get cold air at low rpmis this it?
Automotive Expert
both symptoms sound sounds like you are low on antifreeze. It seems like you got more coolant into it so it isn't overheating anymore but not enough to keep the heat working all of the time . You may want to take it somewhere that can use a vacuum system to fill it to get all of the air pockets out .

Alright thanks.
Automotive Expert
You are welcome.

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