I have read the overheating problems of others and do not see a situation that sounds like mine, so here goes.

The car is a 2006 HHR 2.4L. It overheats at idle only, cooling back down when going down the road or when running at higher RPM sitting still.

My problem is not a dead fan. After I shut the car off, the fan continues to run until the car is cooled down, so it is doing its job. I don't see any leaks and my coolant level is good. I replaced the radiator cap and it did not resolve the problem (always try the simple stuff first).

 

How did you determine it is overheating.....temperature?

 

Yeah, the read-out shows it climbing into the 240's and the gauge climbs into the red. That happened once in stop and go traffic. At home, I have seen it climb into the lower 230's and don't let it go red before shutting it off. Running the engine at constant high RPM cools it back down.

 

I'd be checking my antifreeze level... if thats fine, then t-stat..

 

How about a low flowing water pump...going down the road adds extra air and or the extra rpms is enough to add more flow, same at high idle standing still

 

I've got a shop that will swap out the thermostat for me for $50 if I provide the part and the Dex-Cool. So I'm taking it in this afternoon and will let you guys know if that fixes it. After that, I'll try the water pump. Everyone wants $300-$400 for that job.

 

I'd guess at a T-stat or water pump.

The thing that I question is .....STANDING STILL AND RAISING THE RPM, which drops the temperature. These cars do not have clutch fans, or the like, so "racing" the engine shouldn't cool down the engine. The fans mounted to the radiator are strictly electric, engaging on demand within certain operating parameters and software.

Thus MAYBE slow coolant movement.

 

What would cause slow movement of the coolant?

 

A "stuck" thermostat, if its stuck closed that restricts coolant flow.

A collapsed lower coolant hose, or a silted up radiator core will also do it along with a bad water pump impeller.

 

It appears to be fixed after replacing the t-stat. I looked at the old one and the rubber on it was in bad shape. I have a steady 207* at idle now and now more climbing temps. Going down the road it stays around 198*-205*. Hopefully the problem does not somehow reappear because for now, it looks to be fixed. The shop only charged me $30 to change out the t-stat and put in new coolant (I provided the part and Dex-Cool). I gave the mechanic $10 as a tip and told him to eat steak tonight.