I always park the HHR front end higher when I fill the rad with Dexcool, either in my driveway which is 6 inches higher at the garage then the street end! This helps get the air out of the system!!

 

And I have never had the problem!

 

So I do a complete flush. I remove the thermostat and fill (radiator cap hole) with dexcool, until I see coolant inside the thermostat hole. I reinstall thermostat and thermostat housing. I disconnect the lower radiator hose from the thermostat housing. I continue filling with dexcool until it pours out the radiator hose. I reattach the hose to the thermostat housing. I top it off and then start the car with the radiator cap off. The level drops and I top it off again, it took less than a cup of dexcool. I try again but the level does not move. I put the radiator cap on and start the engine, it sits in the driveway and heats up to 230 before I get scared and kill it. The fan is running but it does not make a difference. So what do I look for now?

Btw when I had the new thermostat out I put it in a pot of boiling water to make sure it was opening.

 

How do I check the water pump?

Could it be the radiator?

After reading about an air bubble. maybe I need to get a radiator vacuum pump and try that?

Since there is no oil in the coolant and no coolant in the oil, the head gasket is fine, right?

 

If I rev the engine up to 2K, it starts to cool down some.

 

It might require a few drive cycles with the heater on to run the coolant thru the system!

 

I drove it to the 7-11 which is about 2 miles away and it hit 230°, so I killed it and waited 10 min for it to drop some before I drove back home. I am really lost on this one.

 

I am pulling the radiator in the morning.

 

Before pulling the rad, I'd swap that temp sensor out with the original one. I've had them go bad before, and the temp would ramp up very quickly once it was warmed up, giving a false reading, yet it seemed to work just great at low temps.

 

Why? Your very 1st post says you have a new radiator.

So. I'm going way out on limb here but I recall a post or thread from way back. Seems an owner installed a new radiator but his car still over heated. Come to find out, he had forgotten to take off the protective shipping cap on one of the radiator outlets when he installed it. Of course the coolant could not flow through the system because of this.

I know. It's a long shot, but......................