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Ask Gm Tech (Cam) Your Own Question
Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1685
Experience:  GM Grand Master Technician 2007. 14 year experience.
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No heat up front. its not the blend actuator. I removed the

Customer Question

no heat up front. its not the blend actuator. I removed the actuator and moved the door manually. still no heat in the front. good heat in the rear
JA: Have you checked to make sure the thermostat is working? What about the coolant level?
Customer: coolant level is good. and the rear heat is good. the heater core lines are both hot
JA: What is the model/year of your GMC?
Customer: 2001 Yukon 1500xl
JA: Are you fixing your Yukon yourself? What have you tried so far?
Customer: its loaded
JA: Anything else you want the mechanic to know before I connect you?
Customer: I am fixing myself.
Submitted: 8 months ago.
Category: GMC
Expert:  Jared D replied 8 months ago.


Have you tried back flushing the heater core yet? We see these trucks in with plugged up heater cores fairly often. If the heater hoses are warm, and the blend door is working correctly then there is likely a coolant flow issue. The air volume out of the vents seems ok right?

Customer: replied 8 months ago.
air flow is good. In cabinets air filter is new.
Guess I thought the return line wouldn't be hot
Expert:  Jared D replied 8 months ago.

I've seen this engine heat up the return line backwards when it's sufficiently restricted. I usually get a little concerned when the return line is just as hot as the supply line. That means that the heater core isn't taking any heat out of the fluid as it flows through. The return line should be slightly cooler than the supply line.

The engine seems to run at normal operating temp right? Not too cold?