[olddog]

I had a problem getting all the air burped out of my car. I had air pockets in the top of the heads. The engine would gurgle when you shut it off. I finally backed it over a steep bank and got another 1/3 of a gallon in it. It may not be your problem, but make certain it is not.

Just for the record, water has a higher heat capacity than glycol. I'm not sure what the GM coolent is, but you will get more cooling with water than glycol.