If the temp goes down that means the fan is running. the T-stats job is to keep the temp ABOVE 180F. "Normal" highway temp is 185F- 200F, stop and go it can get higher, over 230F is dangerous.

 

I wanted to get in on this convo as well because I would like some info about my current issue. I have a 2011 HHR LT 2.2L. I currently have a P0172 error code. I was assuming it could possibly be a dirty MAF/O2 sensor or needing to replace but i noticed the convo here about what temp the coolant should be showing. I did a 20-30 minute drive home from work and noticed my coolant level shows it between 172-176F on my dashboard display. Backstory of car is I bought it off a coworker helping a friend sell it. Didn’t get very much info on maintenance aside from being told a new catalytic converter was installed along with new O2 sensors. It currently has 118k miles on it.

 

Welcome to the site,
https://www.obd-codes.com/p0172

The code usually indicates an exhaust leak at the flex pipe.

 

You should have a P0128

 

Get a ACDelco 131-158 thermostat

 

That doesn't seem right. Wouldn't the leak be before the o2 sensor?

Here's a good read. https://www.chevyhhr.net/forums/prob...-please-60572/

 

Flex pipe is before the O2 sensor on most. IIRC, only the 5 speed is on the manifold.

 

An ‘11 2.2 has the first O2 sensor between the flex pipe and the catalytic converter

 

Ok, I see now.