Hello. So, as of more recent I generally watch the temperature gauge in the HHR. For the past few days I've noticed the temperature gauge running higher than normal especially at idle. A couple of times it has gotten as high as 221 degrees Fahrenheit. What I found with the car today with the car showing 190 degrees Fahrenheit is the upper hose near the cap was warm, both hoses going to the heater core were warm but, the bottom hose on the driver's side was cool to the touch.

So far there is a couple of things and from what I've researched so far, is that one cause could be a faulty thermostat. The other could be that the water pump could also be faulty. I'll also add this and went back through my service records. At around 190k miles the timing chain was replaced, the cylinder head was redone or might of been replaced (that's another story) along with the headgasket. I see Felpro was used for the HHR.

But, for some odd reason I don't see that the water pump nor the thermostat were ever replaced at that time. Why? I don't know but, our HHR is now currently at 238,3xx miles about 98% highway miles. Normally, the HHR usually runs around 194 degrees and sometimes it does get back there but, most of the time these past few days it runs at 199-201 and if it idles at a drive through it does go up until I start moving again.

It is cold and has been snowy here plus I don't have a garage so, I'm thinking to first try to replace the thermostat with an AC-Delco Professional or OEM GM one if possible. Just to clarify the electric fan does work. Just wondering about thoughts on this? Thank you in advance and again.

 

You didn't mention anything about the fan. It should run if the AC compressor is running or the coolant reaches 219F then turn off when the temp gets down to 179F.
It is next to impossible for the t-stat to fail closed.
It is possible the heater core has a air lock. Do you hear a "gurgling" coming from the waterfall area?
Have you checked the coolant level UNDER THE PRESSURE CAP?
If you replace the t-stat USE ONLY 131-158 Not "replaces", "like" or anything else. The GM Professional is junk and the dealer will give that to you if you ask for OE.
T-stat and water pump are not maintenance replacement parts.
"Normal " operating temp when moving is around 190F
Any car part that is labelled "professional" is cheap junk made good enough so that it is the next guys problem.

 

Hello. From what I can tell the fan is running. As I said, I believe the car has the original thermostat which means it has 238,3xx miles on it. Now, it could of been replaced without my knowledge with a parts store brand but, I don't know. I will add that I did drive the car over a 100 miles yesterday and checked the lower radiator hose twice. The result for the lower hose was the same even with it running was cool to the touch. The upper hose was warm and the heater core hoses were warm just not that lower hose. Would that symptom be indicative of a failed thermostat? Anyways, I'm just trying to clarify before I have parts replaced and work done.

 

But, you are not able to open the hood when the AC is on, or remove the pressure cap (engine cool) and use your mark II optical sensors?
What does mileage matter to a part that is not a maintenance replacement item that does not usually fail closed? That beefy spring on the t-stat would have to break to cause it to fail closed.

 

Any sign of leakage, like a dropping coolant recovery tank level?

Water pump failure is usually leaking seals (and significant dripping coolant. GM says an occational drip or two is seepage and not a failurure) For one to cease circulating water is pretty rare ( but not impossible in cars this old.) Thermostat failure, on the other hand, is pretty common. So is a partially empty cooling system. It's a pretty easy job to dump all the coolant and renew it (probably about time anyway) while installing a brand new OEM thermostat. Make sure you get all the air out and then see what happens.

 

I didn't see my last post here so, I'll try again. The fan is on and I have the A/C Switch on along with defrost even though it's 20-25 degrees outside. I did have the cap off and did see coolant in there but, not sure if it was moving well. The upper hoses are warm and the lower hose is cool to the touch even after a 100 mile drive. I verified this twice. The only other thing I notice is looked like coolant pushed out of the overflow bottle but, hard to tell? Burped the cooling system same result. Didn't see any milky oil but, will verify again. As I stated prior cylinder head has been off engine, headgasket replaced, timing chain replaced with Cloyes about 50k miles ago. I don't know if the thermostat was replaced with an aftermarket one at that time but, it is possible.

 

The coolant under the cap should be full. It is difficult to tell if the coolant is flowing

Coolant is supposed to flow in and out of the bottle. When engine is cold the coolant should be at the bulge in the bottle, there is a very hard to see mark on it. Don't over fill.
When in defrost mode the AC compressor runs.

 

Change your thermostat and replace the Dexcool and burp your cooling system. You will be surprised that Dexcool has only a 5 year life span, after that it breaks down and can start to crystallize.
as Donbrew stated only use the AC Delco 131-158 180 degree thermostat.

https://www.chevyhhr.net/forums/how-...-system-60614/

 

A link to RA for the correct thermostat

https://www.rockauto.com/en/catalog/...hermostat,2200

 

This one

That price is in CAD