2002 Cavalier overheating...Bad thermostat?

[nearles]

I have a 2002 cavalier that runs hot. When i dont have the heat on it is fine, but once i turn on the heat it starts to overheat. When i come to a stop the heat stops coming out of the vents. Any help would be greatly appreciated.

[Labman]

That sounds strange. Is the fan running when it over heats?

[T-Man 91]

That is a bit strange. Normally, when you turn the blower motor (Heater) on, it will drop the engine temp. This is just a hunch on my part, but I think you are looking at a cooling system malfunction or a problem with the engine. The thermostat regulates the amount of coolant that is dumped into the engine, which may not be giving enough coolant or the other way around.. Have you checked your oil level / condition? Check for any sludge build up around the oil cap as well. This could be the problem as well. Simply, it could be a number of things, but I am doing my best to narrow the list. Bad oil can cause your engine to run hot just like running a quart low can cause overheating.

[tech]

It could be one or two problems , it sounds like your heater core maybe pluged up and needs to be flushed out , and maybe your water pump is not pumping the coolant the way it should and it needs to be replaced .

[Sprawler]

Originally Posted by T-Man 91

That is a bit strange. Normally, when you turn the blower motor (Heater) on, it will drop the engine temp. This is just a hunch on my part, but I think you are looking at a cooling system malfunction or a problem with the engine. The thermostat regulates the amount of coolant that is dumped into the engine, which may not be giving enough coolant or the other way around.. Have you checked your oil level / condition cd production online? Check for any sludge build up around the oil cap as well. This could be the problem as well. Simply, it could be a number of things, but I am doing my best to narrow the list. Bad oil can cause your engine to run hot just like running a quart low can cause overheating.

Personally I think a sensor or computer malfunction is more likely. Like you said using the heater should pull heat out of the coolant - no way for the reverse to happen.

[Labman]

Yeah, that didn't make sense to me. I was wondering if the fan was turning off when the heater came on.