02 GT heater blows warm air, then cold, then warm, etc.

[skeelo58]

A few weeks ago my heater started acting up. It will blow warm air for a few minutes, then it will blow cold air for a few minutes, and then repeat the cycle all over again. Sometimes it will do this while sitting at a stop light, sometimes it will do it while driving. Being that I live in the frozen Hell known as Fargo, you can imagine that this presents a problem for me. I replaced the thermostat back in November, so we can rule that out as the problem I believe. Anyone have any suggestions?

 

[Sven the Sexman]

Low coolant/air in the cooling system.

 

[Scottydoggs]

whats the temp gauge doing during all this hot and cold air flow?

seems like a air bound core. try flushing it, and topping off and bleeding the cooling system.

 

[skeelo58]

whats the temp gauge doing during all this hot and cold air flow?

seems like a air bound core. try flushing it, and topping off and bleeding the cooling system.

Temp gauge will fluctuate between 170-200, give or take. I believe it's a 190 degree thermostat I have in there. Temp gauge is independent of the warm/cool air swings though, which is why I've eliminated the thermostat as being the problem. I'll check the level of coolant, and check for any air in there as well.

 

[Scottydoggs]

theres a bleeder on top of the t stat. let the car idle till the fans come on, rad cap off topping it off as needed. when the fans come on, open the bleeder. this way you know the t stat is open. open the screw 3 or 5 turn, leave it open till a stream of coolant come out of it. then shut it. top off the rad if needed, and cap it.

the heater core, take both hoses off the back of the alt bracket and with a garden hose flush till clear water come out the other hose, flush both hoses. put them back on whith the hoses full of water.

remove some coolant from the rad and add new to make up for the water in the core, it will mix on its own.