Whoa !!! 226 Now that would concern me.....

On the water issue.. I just had my Venture Van serviced at my GM dealer here and they did a complete flush and new 50/50 mix with Dex Cool and Distilled Water with a New AC Thermostat. FWIW

Silverfox

 

My thoughts: 1. wrong coolant. 2. wrong filling procedure and you now most likely have air in the coolant system.

 

I would not think that coolant type would make a difference, but sure, I'll empty and refill with dexcool in the morning. Now about the filling procedure, what is the correct way?

 

To begin with it takes just under 2 gallons, 2 if you also fill the the overflow tank.
This works for me:
Fill to top, leave cap off, run till it gets to at least 180F(so the t-stat opens) the level should go down, top off, turn off let cool. Check level, top off, replace cap, run until it reaches over 180F, let cool, check level, top off.

 

The wrong coolant type won't be the cause of your over heating. I was just stating it's wrong to use that generic, "fit anything" coolant.
You really should take a look in your owners manual for specifications and recommendations.
Here's a paragraph from the owners manual:
Notice: Using coolant other than DEX-COOLŽ can
cause premature engine, heater core, or radiator
corrosion. In addition, the engine coolant could
require changing sooner, at 30,000 miles (50 000 km)
or 24 months, whichever occurs first. Any repairs
would not be covered by the vehicle warranty.
Always use DEX-COOLŽ (silicate-free) coolant in
the vehicle.

Also, donbrew gave a pretty good description on filling the system. In your post, I didn't see anything about warming it up with the cap off until the thermostat opened. That's where I assumed you could have gotten air in the system from not doing the "burp" of the system.
HHR's seem to be a little tricky to get the air out when refilling. If doing it without a specialized filling machine, it has been said that you should at least have the front of the car elevated somewhat when doing this work.

 

Seems to me I also saw somewhere you should turn your Heater Switch to the Full High Heat position for circulation.

Silverfox

 

Yes, "they" all say that. It's an artifact, I think.

The heater core is always hot. That's what the bypass hose is for, it bypasses the t-stat. The cabin temp is regulated by air flow over the hot & cold coils. Also the reason you can have warmed A/C air and warm feet before the temp gauge gets to 180F, or dry warm air on humid cool days.

The older systems regulated the hot water flow through the core. And then as an after thought you could turn the A/C on. Remember the early 60's Ford/Mercury with "Factory Air"? It looked EXACTLY like an after market under the dash installation.

 

I bought 6 gallons of distilled water. I am in the process of doing a complete flush, following DonBrew's suggestion of leaving the cap off, heat it up, top it off, cool it down, top off and repeat. Seems to work but is spitting water all over the top of my alternator. Upon a closer look, the air bubble has to be caught up in the lower radiator hose. Seems like if I disconnect the lower radiator hose from the thermostat housing and fill the radiator, this will eliminate most of the bubble.

So here is my question. Every HHR I have ever seen has a thermostat housing with an additional port that is "always" capped off with a rubber cap. What is this port for? I see it as a potentially easier way to get the bubble out.

 

It's for other applications. For HHR only the 2006 2.4L to run into the oil cooler.

If the alternator cared if it got wet it wouldn't live in the open air. You could put a piece of plastic over it to guide the water off.