Loose/dirty pin in one of the connectors/

 

Pretty basic but nowhere did I see that the coolant level had been checked. Three of my 4 HHR’s experienced coolant temp weirdness that was totally cured by adding a little coolant to the surge coolant recovery tank and going through a few warm up/cool off cycles from normal daily driving. Makes me suspect that’s unlike many other cars, this one is a bit sensitive to the coolant being even slightly low.

My question would be: Have you checked the level at the surge tank? Have you found the system full at the pressure cap? How sure are you that the coolant is the correct mix of Dexcool? Just how cold was that exceptionally cold day?

If you going to park a car outside all winter, just take the battery out and store in a warm place. If not, just plan on buying a new battery. You should either top of the charge every month or battery tend it, but you’ll probably get away without doing that.

 

Only 2006 and some 2007 have surge tanks.

However, if the coolant is low enough the temp sensor will be reading air temperature inside a bubble. But that does not explain --- display or oil pressure reading ---, those 2 together lead me to think "broken or burned wire".except they don't have a wire in common. Connector pins maybe.

 

Huh. Guess I don't know what a surge tank is. Does it by definition have a pressure cap? You know that not-really see-thru tank right behind the radiator where you can't quite see if the level is right? No pressure cap, just a sloppy snap-on lid. What's that called? A coolant reservoir?

I have no better ideas for the absent oil pressure reading.

 

That would be the engine coolant recovery reservoir tank.

 

2006 models have a surge tank; it is a tank under pressure, function like a coolant reservoir. Others have a coolant recovery tank with no pressure, designed to receive overflow from heated coolant and return it when the engine cools down and creates a vacuum. There doesn't seem to a standard nomenclature.

Surge tank

recovery tank

 

OK, thanks! I was familiar with both types. Probably doesn't make any difference in this case. Seems an advantage to the recovery tank is you can add (some) coolant to a hot system, but the disadvantage is that the coolant gets exposed to oxygen, maybe?

I had a 2003 Malibu, bought new, with a badly-molded surge tank that slightly leaked at the extremely reluctant cap from day one, plus the material was so hazy you couldn't see the level. Dealer insisted adding coolant periodically was normal, so no warranty. Don't know why it took me so many years to replace it with a Dorman unit that was much clearer, which didn't matter because I no longer needed to check the coolant level every couple of weeks. Except for that it was a pretty good car. Except for the lower manifold gasket they wouldn't fix for me and a gazzillion other victims. And fan motor resistor pack. And...

But I still liked the boring thing and kept it for 16 years. Then I gave it to my brother-in-law and he wrecked it three weeks later.

Gotta love GM.