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Chevy Cobalt overheating

I have a 2005 Chevy Cobalt(arrrrgghhh) and I am experiencing a problem. As long as I’m driving the car is fine, but if I stop at a light or any other time I’m idling, the coolant temp SKYROCKETS. What is the problem? The coolant level is fine, so I don’t know what to do.

plugged radiator? When moving you disperse enough heat, but it can’t sitting still. Or, fan/fan relay won’t turn on the fan (do you hear the fan go on when you are sitting?)

I add the possibility of a worn water pump.

the car defintely starts to run rougher whenever it starts to heat up. that could possibly be the fan?

if it is the radiator, is that expensive to fix?

is a water pump an expensive part to fix?

Not compared to other things that could go wrong if it is allowed to over heat. Frequent change in temperature where it never really gets into the red, but near, can cause head gasket problems or worse. So I would have it looked at sooner rather than later.
The obvious question is coolant level as well.

Yes, it could definitely be the fan. Or its relay or its temp sensor. Your symptoms would be typical of an inoperative fan. I suspect the car running orugher is not the fan starting, but a symptom of the oevrheating.

You can verify whether the fan is operating by simply opening the hood and looking. Be careful not to let your necktie or any other thing fall into it.

Is it actually overheating (coolant needle into the red, or whatever “abnormal” indication exists), or is it running warmer than usual, yet within normal ranges?

For example, my last car ('98 Contour) had a 195F thermostat, but the electric cooling fan didn’t come on until 212F. This meant that, while moving, the needle sat right in the middle of the normal range (helpfully marked “NORMAL” on the dash…say, between the “R” and “M”), but when stopped, the needle would go higher (between the “A” and “L.”) Still, however, withing normal operating limits.

For whatever reason, this freaked owners out. Despite the fact that the needle is within limits, owners would worry because the needle moved towards the high end.

So, if the temp guage stays WITHIN the normal range, it probably just means that the electric fan is designed to come on at a higher temperature than the thermostat opens at.

If the temp guage EXCEEDS the normal range, though, and/or the car is making steam, you have a problem. Run the heater full-blast (fun!) until temps drop into the normal range and/or you get underway again.