Heater Core Problem

theroosta · January 2, 2012

This is only my second post. Ive been having issues with my heater in 2005 GMC sierra first i thought it might be an issue with one of the actuators but after following the recalibration procedures i found that those were fine i could hear them reset and the airflow being redirected. then i thought it could be the ac controls. But after doing some more research last night i am pretty sure its my heater core. I just went out and started my truck and let it run for about ten minutes and went out to check the hoses to see if they were both hot, but low and behold only the right hose is hot and the left hose cold. Does the mean that I definitely need a new heater core or can i simply flush it out. obviously it is stopped up.

txab · January 2, 2012

This is only my second post. Ive been having issues with my heater in 2005 GMC sierra first i thought it might be an issue with one of the actuators but after following the recalibration procedures i found that those were fine i could hear them reset and the airflow being redirected. then i thought it could be the ac controls. But after doing some more research last night i am pretty sure its my heater core. I just went out and started my truck and let it run for about ten minutes and went out to check the hoses to see if they were both hot, but low and behold only the right hose is hot and the left hose cold. Does the mean that I definitely need a new heater core or can i simply flush it out. obviously it is stopped up.

Try flushing the core thoroughly before replacing it. I'd reverse flush to start with then later try flushing the normal direction of flow

Silverado4x4 · January 2, 2012

This is only my second post. Ive been having issues with my heater in 2005 GMC sierra first i thought it might be an issue with one of the actuators but after following the recalibration procedures i found that those were fine i could hear them reset and the airflow being redirected. then i thought it could be the ac controls. But after doing some more research last night i am pretty sure its my heater core. I just went out and started my truck and let it run for about ten minutes and went out to check the hoses to see if they were both hot, but low and behold only the right hose is hot and the left hose cold. Does the mean that I definitely need a new heater core or can i simply flush it out. obviously it is stopped up.

Try flushing the core thoroughly before replacing it. I'd reverse flush to start with then later try flushing the normal direction of flow

As txab said she is clogged. Back flushing is in order.

CapitalTruck · January 2, 2012

A shop near me occasionally has luck using compressed air to blow them out.

TJay74 · January 3, 2012

I am in the smae boat, problem is all of the crud in the rest of the system. I had mine flushed once already and will have it done one more time in the coming weeks if I dont reverse flush it first on my own.

theroosta · January 3, 2012

OK guys thanks for the quick replies but i feel like a retard because the darn thing was about a gallon low on antifreeze i filled it to the proper level and wala!!! Heat

txab · January 3, 2012

Now you need to discover why you were a gallon low on coolant. Water pump/gaskets are a suspect, as well as the known Castech head issue

theroosta · January 4, 2012

Castech head issue??? please explain, I have only had the truck for like 7 or 8 months so it could have been low when i got it. but still it lost it at some point. Unless someone changed the water pump or radiator ect... and did not fill it all the way up ill just keep an eye on it for now.