I have a 2008 HHR SS with just over 101,000 miles I've had it for just over 8 years and as far as I know, never had the coolant system serviced. At the end of last summer, I noticed the water temp gauge getting to 215-220 in the Oklahoma heat in traffic. The coolant was a bit low so I topped it off. I didn't drive it much during the winter here, in fact, I don't drive it much at all. Now May, I notice it typically runs 195-205 which should be normal with the (I assume original) 195 thermostat. Lately, I've noticed the temp ranging from 195-215. What's odd (to me) is the temp will fluctuate between 195 and 215 as I'm driving at a steady 50-55. When I stop at a light the temp (at say 200) may go up or it may not but when I take off it'll climb to 210-215 the eventually go back down to 200-210.

I can see running at a constant speed and constant load the temp may vary a couple of degrees but 10-15 degrees of variance seems a bit excessive. I assume it has the original (or maybe aftermarket) 195-degree stat since it gets to that temp before fluctuating. One question is if I change the 195-degree stat to a 180-degree stat should it run in the 180-190 range and only climb higher in traffic?

I know a properly operating thermostat doesn't cause overheating but with the 195-degree stat, there are only 15-20 degrees to play with. With conditions being equal, would the 180-degree stat help keep it in the 15-20 degree heating range (i.e. 195-200 tops)? And, since the original calls for a 195-degree stat would changing it to a 180-degree stat have any effect on my engine monitoring systems?

Thanks!

 

Factory thermostat is 180 degree. If you've never serviced the system (as you say,) I sure hope that's not original 14 year old Dexcool in there.
Do yourself a favor and service it. A flush and refill is needed and you should replace the T-stat as well. Remember. Only a genuine AC Delco thermostat. Other brands don't seem to work well in the HHR Ecotec engines.

 

Your coolant is elementally an electrode. It needs to be changed. It can cause cavitation issues as well.
The coolant becomes alkaline and you can actually measure the amount with a volt meter. It's called electrolysis and and can eat the fins off the water pump.

 

ACDelco 131-158 thermostat

 

Of course use Dexcool 50/50 mix, and burp your coolant!

 

The basic problem sounds like a fan or fan controller problem to me. But, yes Dexcool has a 5 year shelf life regardless of miles or hours.

 

I appreciate the information on the original stat rating. I guess I just assumed since it's always run in the 195-210 range a 195 stat was in there. Guess it is time to get it serviced and replaced. Thanks, everyone. FWIW, I checked a few places on the AC Delco stat, O'reilly's is $66 and Rock Auto is $36. Looks like I'll be getting one through Rock Auto, eh?

 

Don’t forget the discount code!

 

The t=stat temp is the LOWEST operating temp; The fan and radiator try to keep it from overheating. The t-stat is mostly there to get the engine warmed up to 180F quickly, without it the temp may never get to 180F.

 

The original LNF in my SS ran at 194*, At the time, I thought that was normal.

My new engine runs at 180*. The one time it got hot was when the cooling fan went bad.