Thanks for posting this Smokewagon. 2007 HHR 2.4 original owner with 77K miles. A/C and gauge cut out this weekend. when it cut back on, the digital reading is very low - 160. so I must have a bad stat. Thanks for the detailed r&r.

Thermostat problems!
 

I had this same problem on a 2006 Malibu SS 3.9 V6, the thermostat gasket can easily be rolled over (which this one was) during installation. This results causes the thermostat to not close completely and engine not to ever reach the temperature the engine temp. gauge needs to see resulting no power to the A/C compressor. Granted this may not be the same on my 2011 HHR, but I'm willing bet the thermostat/gasket design is the same. One last thought concerning the thermostat I now use only an A/C Delco brand after reading other owners having so many problems with other brand thermostats. This is not to say other brands will not work but know the one I removed from the 2006 Malibu SS was not an AC Delco design, it was from who knows sources

361 days after replacing my factory-installed stat, this one seems to be going. (I figured, hey, the original lasted 7 years, why not put in another GM 12622410?)

Yesterday= outside temp 100° F, coolant swung between 153° and 181°. Today= outside temp 77°, coolant varied between 158° and 181°. Later in the trip, it stayed around 180°.

Maybe it's the sensor this time? (Just reading low?) But if that's the case, why the big variation while I'm driving? (And it's not getting up to that 193° area.)

(Fortunately, it hasn't shut done the A/C yet!)

Comments?

Air still trapped in the system?

It's a simple enough job to pull the current thermostat and check it to see if it is jammed open.

My guess is t-stat center gasket failed, the t-stat is stuck open, anyway. I believe that number is the old design.

This shows four other superseded numbers, but doesn't detail which is the latest version

GM OEM Engine Coolant Thermostat 12622410 | eBay

Two days in a row it's been fine. WT....?

I burped the system when I replaced the stat. (Recognized that gurgling sound in the dash.)

I think I'll go with a Stant next. I e-mailed them asking what the difference was between their 14698 and 48628, but haven't gotten a reply. Both are spec'd for the 2.2L, and are to replace the OEM by part number. (And it costs less than the GM part.)

Did you read any of the preceding 12 pages?

The after market t-stats and the older GM have a rubber gasket on the valve, The new GM has metal on metal seal at the valve. You can see it in the pic in #126, the center not the housing gasket.

It is that rubber gasket that fails.

The difference in the Stant numbers is the medium used in the plunger. One is wax the other is something else.

The GM part is cheaper or within a dollar on eBay the last time I needed one. When you are talking $30 does $2 really matter to you?

I just picked these at random.

I'm out! I've replaced at least 7 Stant's