Mostly because the Shop Manual says not to; but it does go on to say because anti-seize defeats proper torquing and can therefore strip the AL heads.

Steel plugs Vs. Al head. Put lube on the steel=overtorque.

 

Ok, did a compression test. Here are the results:
#1- 175
#2- 175
#3- 173
#4- 180


From what I read that's really good right? Also installed new spark plugs, old ones were part # 41-981

 

Yes, that's pretty darn good. Now if you can just locate that pesky coolant leak...

 

I wonder what book gave that number. I can't see it crossing over to anything that fits in an HHR. Well an Autolite number that fits HHR does crossover.

Anyway they have been replaced before. AC Delco 41-105 will last 100,000, I don't know about platinums.

For one thing they are Double Platinum, which might explain the missing whiskers.

The AC Delco DP is 41-834.

 

So would that rule out an internal leak? What about intake manifold gaskets? I know its an issue in other GM engines. What about these?

 

Completely different situation on the Northstar engines. There is no water near the intake gasketS, there are 4, really O-rings.

Could be head gasket, some have reported the water pump was leaking into the crankcase. Could be one of the rubber hoses or caps has a tiny leak, if steam is escaping you would never notice dripping.

 

Ok, what would be a logical next step then? I do see a little glistening under the radiator cap, but I just took it off a few days ago when this all started, to check the level, it doesn't seem to be growing. Cap is only a little over a year old. Where is the water pump? I know its internal but I haven't found any posts on where it is.

 

Water pump search , yielded these

https://www.google.ca/search?q=2.2+H...&client=safari

 

Thank you, I had just been searching this site, and whatever results my lovely windows phone was bringing up:/
Sometimes I forget how much better google works.

 

Check out our "How-To" library. There is a step by step.
"How To" Tutorial Library - Chevy HHR Network
https://www.chevyhhr.net/forums/how-...acement-56476/