I have a 2008 HHR SS that overheated the other day. I replaced the thermostat, refilled the system with Dexcool and jacked up the front of the car and ran the motor with the cap off to burp the system. Drove it around and it still is overheating. I also have no heat... the hoses to the heater core seemed cool to the touch..so I took the hoses off of the heater core and stuck a garden hose on one end of the heater core turned the water on and the water did cycle through the heater core ....so I know that the core is not plugged. Any ideas? Thanks

 

From your description, sounds like maybe the coolant is not circulating. Waterpump may be bad. If it's not circulating, the radiator will most likely be cool to the touch when the engine is overheating.
How many miles on your SS?

 

I can see the coolant moving through the hose at the cap when I was burping it....I didn't check if the radiator felt cool through.....135,000 miles..radiator was replace at around 40,000 due to hitting a deer.

 

How did you determine it was overheating? I've had a sensor go bad in a non-hhr, causing the temp gauge to peg to the top - I did the same thing (flushing the heater core), and even pulled the rad and found it was spotless before finally checking the temp sensor.

 

coolant coming out of the overflow, just a little though....mainly because of both gages reading over 250... but I still don't get any heat. Didn't get a chance to look at it today.

 

That does not sound good. Any sign of antifreeze in the oil? Or oil in the coolant?

 

no, I checked, that's what puzzles me. I don't know what I'm missing. Would that temp. sensor cause any of this? I did have the DIS gage say F--- for temp. once.

 

No, the sensors only control the readouts on the temp gauges, and control the rad fans. Ahhh, have your rad fans been coming on at all? I believe that at least one fan will come on as soon as the a/c is turned on.

That ---- on the digital temp gauge is often caused by the temp not coming up fast enough during warm-up. And that typically is caused by the rubber gasket on the thermostats movable valve deteriorating and jamming the thermostat open.

 

Pull the thermostat and fill from above until you have coolant gushing out from the engine side.

Test the new thermostat in boiling water. Should open before boiling. Carefully with a heat gun also works.

Unless a thermostat already has a bleeder hole, I drill a 1/8" hole. Obviously, the thermostat should be oriented with the hole as high as possible.

An infrared thermometer is always handy - get one if problem persists, if nothing else to get a second opinion on gauges.

It is easy to test for exhaust gasses in the coolant - AutoZone has a kit they rent. Bubbles going by in flow with pressure cap off, or possibly in overflow tank, could indicate a bad head gasket.//

My guess is that the thermostat isn't opening - most likely because the business end (toward engine) is in an air bubble.

 

Did you test the old thermostat?