I have seen all the other post about this issue, and this is why I asking this question

2008 HHR panel LT 2.4L
170k

About a month ago I had the temp gauge read "---F" and then it thru CEL P0128 and after reading the forum, I had the thermostat replaced and radiator flushed and all new DEX-Cool put in.

So for about 2 weeks everything seemed fine and it didn't have any issues. But for the last 2 weeks it has been reading and not reading intermittently. When working the DIC reads 168-176F when under normal loads, and higher when driving up mountain roads.

T-stat was replaced with a duralast from autozone rated for 180F, new gasket installed too
Fluid levels seem good, always full (under the cap) and reservoir has fluid in it

Been driving in morning temps around 28-50F depending on job location, and the morning it when this issues happen the most, but it has happened in the afternoon.

Last time this happened I stopped for gas after a 30 min drive (temp reading) and when I turned the car on after and started driving it stopped.

Thanks in advance for any input

 

Welcome to the site.

Based on your info, sounds like your new T-stat is sticking open.
There were some threads a while back about this same scenario. Seems that when the old thermostat goes bad, sometimes, parts of the rubber gasket break off and get in your cooling system. After you replace the thermostat, these rubber pieces can migrate back around and get wedged in the new thermostat, thus wedging it open.

Granted, this is a guess, but a good possibility of what's happening.

 

Welcome to the site

X2 to above. Also some of our members had problems with aftermarket thermostats and had to replace there's with a factory one.

 

X3 - especially since you are getting low temperature readings like you say. It is all dependant on how quick it warms up - it will blank out the displays if it does not warm up fast enough (exactly why it can happen more frequently in the morning when it is at a cooler ambient temperature s it chills down at night).

GM makes a better thermostat I believe without that darned rubber gasket on the movable valve. It has been used with good reports so far.

 

to the forum!

And X4, the OEM thermostats are just more dependable.

 

Welcome to the forum, X5 for the T-stat, the spring does not react the same as the GM T-stat causing the issues you are having. you get what you pay for!!

 

So I ended up buying the OEM ACDelco one and replaced it this morning. Tested the one i got from Autozone and it is clearly marked 180F but it opened up (could see thru the seal) at like 165F and I watched it fully close at 158F.

Thanks for the help

Techna

 

Thank you for testing the waters, hot waters, you just proved wha I have been saying all along !!!!!

 

So I have a extra question to ask

My boat has a 140 stat in it, and it runs just fine. Other then the HHR's computer having a issue, would running a lower temp stat cause any problems?

 

YES! The computer expects a certain temp at a certain time. (period).