Oldblue

I’m going to explain here, how to burp the cooling system in the HHR.
It’s simple and effective.
As always, we recommend changing the Dexcool, with Dexcool, a 50/50 mix of Dexcool and water. Every 5 years.
I myself prefer the premixed version, saves time and bother, hey, I’m a disabled guy in my mid sixties!

So, after you change thermostats, or Dexcool or perhaps change the water pump.
Fill the rad hose filler under the pressure cap with Dexcool, right to the top, with the heater on high to open the heater core up to the cooling system.
Now let it cool off , then top up the Dexcool and put the pressure cap back on.
Start your engine and drive around the block, gently, now watch the DIC for temperatures.
Park the front bumper higher then the rear, either the sloop if your driveway can help here or jack up the passengers side front and support with a jack stand.
Enjoy a cold beverage, maybe watch the game, walk the dog. Have a nap.
But let the HHR cool off, I recommend over night but 2 hours or more should do it.
Carefully remove the pressure cap, and top up the Dexcool.
You might do this for thre or four times to ensure all the air is expelled or burped out of the cooling system, it sounds tedious to some , but it works.

I also recommend replacing the pressure cap every five years, but I’m a very old school preventative maintenance kinda guy, and using my methods, I’ve only been stranded once for a dead battery in my 48 years of driving, legally that is.

Oldblue

Here’s a video about the reasons to burp your cooling systems coolant

CHENG

Oldblue,
Thank you for the information! We didn't go to these measures when filling the cooling system. We pretty much filled it, ran it unit go hot with the pressure cap off. let air bubbles work out (or so we thought) and topped off with the Dexcool again. It didn't take much. The engine is new so I would think the thermostat was too. But, we changed it anyway. I tested it and it was wide open around 185° F. It seems like there is insufficient flow but I can't really tell. I will try your method in a few days (I'm busy with doctors until Wednesday). I'm a retired Merchant Marine chief engineer and have had my share of BIG engines getting air bound but not so much small engines. FYI, I turned the heater on high and the coolant temp went UP! Never in my 72 years have I seen that.
I'll let you know how this turns out. Thank you again!

Oldblue

Burping can take several times and be sure to let the car cool over night!
front end high , I’m fortunate to have a sloped driveway

donbrew

That sounds like the heater cores is the problem. The core should be always hot. Fresh air is default then cold air then heated. Not like a 70's heater that is controlled by a water valve.
The only difference turning the heat on is the air has some place to in its flow to.

CHENG

Shouldn't turning the blower on strip some heat from the heater core and thus lower the coolant temp a few degrees?

Oldblue

Not in our little trucklets

greg8453

Lift the front end as high as you can get it and it'll go fast.

boatmoter

I agree on that method,it's effective. I broke down and purchased a vacuum bleeder to bleed and fill the cooling system. I used to use to pull the front up on ramps then use a spill free funnel to get the point even higher. I own a HHR & a PT cruiser & a 2016 Malibu. all 3 are hard to get the air out so I purchased a vacuum bleeder,they work really cool and get all the air out

Oldblue

I’m familiar with the bleeders, but for the average owner to change coolant every 5 years, the burp method works well and is very cost effective (free)