IDK for sure, but it is on the list of covered parts..

 

The only thing that lets me know there is a problem is the "Auto start" will not work.
Car does not overheat and everything seems to work fine.
First time when I took it in they said it was an "O" ring, the other two times it was the stat.
Its about seven miles to work....Thats why the low milage....

 

For those that have not actually seen a stat for the HHR. it has a rubber seal around the edge of the disc, older style stats had metal to metal seals. The rubber seal breaks,expands/comes loose, whatever... it then blocks the thermostat from closing all the way. When this happens the engine will not heat up fast enough. It will show up first usually by the temp gauge, both analog and digital in the display not working. It will eventually also set a code.

There seems to be no telling how long a stat will last. In 70,000 miles I have been through 4 stats. One only lasting 3 month. One lasting 2 years. I will say I have had better luck with aftermarket stats than GM stats, but that's just my experience.

 

I wonder how many factories in the entire world would be manufacturing t-stats, my guess is maybe 3. The HHR t-stat is not "special" in any way, but the gasket and in fact you can buy just the rubber gasket, if you think you are saving money getting "just any old 180F t-stat".

I did go through a time of removing and installing mine repetitively, And I think that the problems with the gasket come from careless installation, you can't just throw it in and tighten the bolts like you can with a cardboard gasket, you need to use a tiny bit of care. AND be incredibly careful with the bolts, the housing is pot metal about 20 degrees softer than the bolt. I stripped one turning a extension with a swivel on the end with only finger pressure, no wrench attached! The good news is the housing is cheap the bad news is the labor is a huge pain.

 

I just bought a used 06 hhr LT with 69500 miles on it. We have had it just little over a month and it has been in the shop 4 times already. The thermostat has been failing causeing the temp guages to zero out and a/c stop working. Just got it back 2-29-12. They said they had to call detroit and get them involved. Said that the factory thermos cause problems so they instaled a after market thermo. Guess we will see if this works. Like I said had it a little over a month and on the 4th thermo. Has anyone else had this problem and has anyone had the solution to resolve it?

 

I look at Ebay. There are many pads, the price from 0.99 to 2.50 dollars.