PontiacBonnevilleClub.com

So, as the bonne is warming up to normal running temp(right about 190) it will blow hot air from the heater, if I go and let her idle for a bit, say I run inside or just sit in the car for a bit because I don't wanna go to work yet, itll go up above 210 in temp but no more than 220 and start blowing colder air. It has never done this before and I've never seen this before either. Any thoughts as to what could be wrong? any ideas of what to check to see what could be wrong?
Note I don't have a garage on base to truely get in and dig into whats wrong, and its a snow storm in chicago right now.

How cold is it outside?, it's possible the heater may be slightly plugged and can't get enough hot water through to keep heating the car.
Have you checked your coolant level?. if it's a bit too low that might give you similar symptoms, in the summer your car would probably run hot.

Roger.

Take the radiator cap off and check for sludge. It could be all gunked up and blocking the heater core.

Failing thermostat maybe?

rustyroger wrote:...Have you checked your coolant level?. if it's a bit too low that might give you similar symptoms...

This. First. It's cheap & easy! Don't just look at the surge tank, pull the rad cap off and have a look in the radiator. Only when the engine is cold, though, please.

I had the same thing happen to my car with it overheating..it was 97 degrees plus..in town..heat gauge spiked into the 210 range. And was not going down..stopped opened the hood let it cool off..then when the weather got colder my temp ran at 165 degrees..suspected the thermostat..replaced it and its been fine ever since..I would do a heater core flush....and a new thermostat..