Fool moon
I noticed you posted that the engine will run hotter with the heater on.
That is what mine is doing.
Just took mine out of storage temp outside in the mid 40,s.
Get on the highway and my as auto with gmtu will go up to 210 then usually back down to upper 190,s then back up to around 205.
Sometimes like today it hit 220 which I do not like.
After I drove it I pulled in my driveway running it was at 205 idling with the heat on
Fan was running lower rad hose barely warm upper hose hot but certainly not 205 hot.
Turned heater to cold turned ac on for 5 seconds temp dropped right away.into the 190,s
Seems like others are experiencing this
Cold out heat on ss runs hot.
Car did not do this before gmtu that I remember but it barely made boost either.
I am hoping.the dealer can at least change the tstat but I probably will get the
All cars run hot if it gets over 240 call us?

 

Thought I would add this link to the same topic
https://www.chevyhhr.net/forums/show...ight=runs+cold

Drove mine in this morning hit 210 it was 34 out
It will be 70 on the ride home bet it wont hit 205.
You would think it would be the other way around

 

Its not the tune..I noticed this peculiarity the first winter I had the car, before the tune...and even played with it..for grins, when its cold and the heater is running and tempt is up, shut heater completely off and see what happens..make sure to turn thermo back to cold too. But,,when you hit a long red light, that sucker will cool off quick. Almost seems that the heater is diverting hot water, that is rerouting it away from the rad so you get max heat inside.

 

That is odd how they do that.
On the way home it was 70 out car ran 199-205 max.
Just for comparison just checked a chevy cruze 1.4 turbo temp.
Ran between 219-222.

 

The cabin heater core is always hot, there is not water control valve to the heater core. It works by controlling the AIR flow over the heater core. The coolant always bypasses the t-stat to the core, that is how you can get warm air before the coolant reaches 192F.

Look more toward the intercooler and radiator fan for SS coolant temp fluctuations.

 

Don
That's the odd thing that makes no sense to me
Of course I am use to older non turbo cars.
But the odd thing is some if the hhr ss' s like mine
Will run hotter temp wise at least according to the computer
When its cold out.
Even if I do not turn on or change the temp setting.
Its almost as if the car reads the inlet air temp and says hey lets run hotter and vice versa.
Then I would think if I turned the heat on full blast roll the windows down it would

 

I do not know anything about turbos. The t-stat keeps the coolant hot enough not cool enough, it opens when the temp gets to 192F. then stays normally open. I have no idea how the intercooler works into the equation, just guessing that it does, that would be the only point that the computer could have anything to do with changing operating temps (and I don't know that it does,or not).

 

Thermostat controls the rate of heat increase..holding back flow to help speed up the heating process...after that its the 'size' of the thermostat opening that actually controls what temp the motor runs at...
These things have a heater bypass valve, i suspect this is what makes it divert from thr rad to the heater core..since the heater core is smaller it has less cooling then the rad..just a guess..

 

My first post! Not sure if pitbull is stilling having the overheating issue. But I experienced nearly the same symptoms for a little over a year in my 09 SS. I had the overheating thing down to an art. 195-205 was normal range. When the temp fluctuated between 205-215 it wouldn't be long before overheating would occur. Also, at 205-215, it meant that I needed to add coolant.

When this issue first occurred, I took my SS to a local shop and they kept it a couple of days trying to find a leak. They didn't find any issues. So, I lived with loosing a little coolant over time and having to add coolant every now and then.

Eventually, this past November, the issue got worse and I took it to a Chevy dealer to have it checked out. My SS had 97k on her but was running great. However, I noticed that I was beginning to loose a little power. That wasn't the reason that I took it to the dealer. All of sudden, I was having to add a bottle of coolant every week. Obviously, that wasn't close to normal.

The dealer kept my SS for one month. They couldn't figure out what was causing the problem. The lead mechanic tried one thing after another, replaced parts, etc. He finally cried uncle and found an internal leak from a cracked block.

Practically everything (radiator, hoses, turbo, engine and all parts) under the hood was replaced under the power train warranty or was included free as a curtisey for keeping my car for so long.

So, new under the hood and she runs like a top.

 

09blks
glad to hear that the dealer took care of that.Too bad they took so long to diagnose that.
I know that if I was loosing coolant I would be looking for a leak right a way.
I have read on the cobalt site that for some reason at least the 09 cobalt motors are more prone to having issues with the engine block than other years.Unfortunatley I would have to assume that the same would be true with HHR SS Lnf motors unless there was some reason since they where built in Mexico that the motors where built at different times which I doubt is true.
On our race motors I always to a pressure check of the coolant system and can usually pin point a coolant leak pretty quickly surprised the dealer did not do that right away in your case.
Guess I better suggest they check mine next time in or better yet Check it myself but I am not leaking or loosing any coolant in my case and I think in most others with the temperature running hotter when colder.
I did have a theory the other day that somehow the inlet air temp when cold was being looked at by the computer and therfore when its cold out say 35 degrees the computer knows that and possibly diverts coolant differentley ,I know makes no sense but any how.
I took off my air cleaner lid assuming it would pull in warmer air from the engine bay.
which i can confirm by datalogging next time .
Anyhow lid off drove to work car went to 205 then regualated right back to 199-203
on the way home it pretty much stayed between 194-199 since the temp was around 70.
I know makes no sense with air cleaner lid being off that the engine would run cooler to me unless the computer was doing something such as saying ok hotter inlet temp lets change coolant flow in some strange way .
what makes sense to me is that cooler inlet temps the car would run richer and therfore cooler or vice versa inlet temps higher with air cleaner lid off runs leaner and hotter.
very strange but seeing how the chevy cruze that I tested with a turbo was running at around 221 seems to show me that 205 210 215 etc is not so bad.