My 2009 HHR seems to be losing coolant someplace. I need to add quite a bit of coolant about every 3 weeks. I don't see any leaks under the hood or on the ground under the car. I also don't find any wet carpet where a heater core is leaking. There is no sign of water in the oil or oil in the water. I usually know it's low when the fan stays on for a bit after I park it or by watching the temp read out and it gets above 217. The car has 35,000 miles so I'm hoping it's not something really expensive to fix. Any ideas? Thanks for your help!!!

 

If you're sure there are no external leaks and there is no evidence of water in the oil, well the news is not good. Sounds like you may have an internal leak. Could be leaking into a cylinder and burning out through the exhaust. Possible cracked head or bad head gasket.
Need to have a shop pressure test and/or dye test the system. Sometimes you can pull the sparkplugs and see one that has been "cleaned" by the burning coolant. It will look cleaner than the others.
I hope that you have actually overlooked some sort of external leak. If not you could be looking at some costly repairs.
Wait a sec. 2009? what about the powertrain warranty?

 

Puddles under the tailpipe after idling for 15 minutes? Head gasket.

I found that the water pump weep hole is at the top of the pump so you really have to look hard to see the telltale drip on the bottom passenger side of engine/trans.

Pin hole leaks are real hard to find, they produce steam not drips. Do you smell coolant.

 

Smelled coolant...no signs under car...radiator cap was leaking just enough to lose coolant....checked every inch of motor, even wash down motor....was the gasket in the cap.....s c

 

You are lucky! But continue checking the upper hose when the engine is cold for collapse, that would be a clue to head gasket.

 

I have recently been watching my coolant level real closely, both hot and cold. I have found that 20 degrees F makes an inch or 2 difference in the cold level in the tank. I kept thinking I was loosing coolant until I checked it today at 80 F.

Maybe we are not really loosing coolant?

Just another random data point.

 

good point Don,
I make a small mark with a sharpie marker on the coolant recovery when the car is cold and has been sitting over night and then I make a mark when its at it hottest point.
Then I have two reference points

 

That's what I did. Funny last week when it was 60 F the cold level was 2 inches below the low line, today at 80 F it was right on it.

 

Mine has alwYs droped sume coolant was bad at one point and it was a rubber hose not clamped on so well. I had thought blown gasket but not the case it still use a minor amount of colant takes a year and a half to realy notice it drop. But colant will evap over time in the revoir.water vapor will escape over time

 

I apologize if I'm bumping an old topic here, but I wanted to report having a similar issue with an '06 HHR of about ~130k miles. I didn't notice an issue until earlier this year in the summer, after a two hour drive. Just about 5 miles from my destination, the car's warning (open door/key in ignition sound) went off, so my first though was that a door had somehow come open. Of course, I wouldn't expect an actual problem! :P But sure enough, a temp. warning light was on, and the temperature gauge was nearly all the way in the red!

Someone who was fairly more knowledgeable in cars gave it a look over when I arrived, and said they couldn't see any immediate issues... But of course, the coolant reservoir was just about empty as far as I can tell. We filled it up with tap water, just for me to experience the same issue about a month and ~300 miles later.

It seems pretty clear to me that there is a leak somewhere, but I'm fairly clueless as to how I can find it. I afraid that I'll have to take it into the dealer and pay for a fix out of pocket, unless anyone can direct me where exactly I should be looking (and what I should be looking for exactly)?