Are you sure the thermostat i working correctly. I've seen a few break and jam shut and cause overheating.And also seen water pump blades come loose and get no circulation. or a radiator that won't keep the temp down on long drives because it's limed up. Just trying to cover all the possible problems. Hope you get it fixed soon.

I forgot to update this journal to show the bigger problem that I found first. The surge tank has a hole in it. I have a replacement on the way.

Working through them one at a time. The thermostat is brand new. The tank is the next thing I'm trying, with a hole, the system can't pressurize which may explain the water pump not working. If that doesn't take care of it, next is the pump. There is no evidence of lime scale on or in the radiator.

Ok, yes it needs pressure or it will boil at 212F/100C with straight water or higher depending on antifreeze/coolant percentage. If this car has an electric fan for cooling, you got problems because they don't kick on until 220 or higher. I don't like that because if you lose pressure it instantly boils over. Also, as far as getting air out after filling, there might be air bleeds you can crack open after it gets the thermostat open, or I like to get it warmed up , then let it sit overnight. It will pull whatever it needs in when it cools from the surge/overflow tank.I never have liked it when that tank is pressured, as too many people will open it when hot and get hurt. The 2 thermostats that broke and stuck shut were both on a Mitsubishi.

Well, if it helps, the car I'm dealing with is an Oldsmobile Intrigue. 2001 model year. I've found some interesting quirks in it's cooling system and I am looking into how to deal with them. I should be getting the tank tomorrow to replace the damaged one. I'll let you know how it goes and hopefully it won't be much harder to fix.

you might have seen this then sounds like air bubble is hard to get out http://www.oldsmobileforums.com/for.....ad.php?p=47435