Last year I noticed that my car no longer has heat. I thought it was my heater core because I had a slight odor of coolant in my car so I changed it out along with a new thermostat and it worked for like a day and then quit again. I forgot about it as it got warmer and now it is cooling off again and I remembered. Any help would be greatly appreciated.
Adam

If it matters, my A/C works like a champ

 

Does it run hot or cooler than normal?

 

no, my temp is normal, not hot or too cool

 

And I don't think it is the rheostat on the panel because I can turn it to hot and it doesn't blow ice cold. It just doesn't blow hot. It is basically cool, no warmth to it at all.

 

My best guess is you have a bunch of crap in your cooling system. If you don't properly keep up with cooling system maintance on LT1's, this kind of stuff happens.

My guess is that your old heater core was all clogged up. You tossed in a new one, and it worked until some more debri clogged it up. Pulling both heater core lines and flushing them with a hose both directions should get it working again.

OR, do that AND do a full cooling system flush as well; my bet is that it needs it. When I say a full flush I mean drain the block (both sides), flush the **** out of it and use a flush kit on the car. It is a lot of work, but this should get your cooling system back into top shape.

 

Yeah, I agree. I just bought a Prestone back-flush kit for like $4 from Wal-Mart the other day. I've just been waiting for a day off of work to do it. I would suggest maybe trying that also.

 

Yeah I thought about that, but when I replaced my old heater core there was basically nothing in it. I poured the coolant out and ran a hose through it and it came cout clean and quick. I may have some crap in the system somewhere. I think I will go ahead and flush it anyway. If it doesn't help, at least I will have a clean system!!!
Thanks guys

 

Well, I got my system flushed this afternoon and it blew warm for a few minutes and went back to somewhat warm. I don't know what is goin on. I am almost out of ideas. Anyone else have a suggestion?

 

This is an old thread, found in a search, but I am having the same exact problem.. Not cold air but slightly warm. Can anyone help? TIA!!

 

Nearly every time, it is a clogged heater core. If it is not clogged, the door that controls mixing of the heated air might not be working. It is mechanically connected by a cable to the temperature control ****. If the **** seems to turn unusually easy, there's a good bet something is wrong with that mechanism.

 

do these cars use heater control valves like TPIs and other GMs.