i just got this 1996 bonneville with 118,000 miles on it and for some reason every now and then the heat turns to cold air and it wont blow hot air out even when its warmed up. woundnt that be a heater core problem??????

now i just turned it back on after 20 min and its blowing hot air again, does anyone have any suggestions???

sounds like air in the heater core

This is a bit outside my area, but I seem to remember there being a valve under the dash, near the glove box I think. And that controls how much hot or cold air enters the car. I could be way off on this, I'm just not sure. But it'* worth a look. I've never had this problem myself so I never looked that close.

my 95 was doing the same thing, i topped it off and burped it then topped it off again and it has been fine ever since.

Check the coolant level in the radiator, not in the reservoir tank. If you have an air bubble in the radiator, the heater core has air in it and you'll get erratic heat/coolant flow in it.

If the radiator is full, when the car is fulled warmed up meaning the lower radiator hose has warm water circulating, run the motor at 2500 for 10 seconds and then repeat that 4 more times. That shoud get the air out of the heater according to the service manual. Then bleed the air at the thermostat housing using the little screw on top.

I have a 1999 SE with now 117,400 miles and it seems to only blow mildly warm air. I just changed the UIM and LIM gaskets and refilled the radiator and bled the lines. I will try cycling the motor to 2500 RPM and then bleed the line again.

But would air in the system also cause the temp gauge on the dash to cycle between 195 and 160 degrees constantly while driving 30+ miles?? Could this be a bad thermostat? I already replaced the thermostat once when it was stuck open right after I bought the car 2 months ago.

Sounds to me lik eyou have a 180* thermostat with the PCM still programed for a 195*

Hmmm the guy at NAPA could have grabbed the wrong one off the shelf...

I knew I should have just bought another new t-stat to install when it was tore apart.

Thanks

thanks guys for all the info i will try these steps and hope for the best.