Originally Posted by austin944

You could try bleeding a few more times. What I do is attach a coolant pressure tester onto the overflow tank and pump it up a little with the bleed screw open, which helps force air out the screw. If you don't have a pressure tester you can put your mouth on there and blow hard. Sometimes I've had to do this several times. You don't want to introduce new air into the system via the bleed screw.

The pressure tester can also be used to check for trapped air. If you pump up the pressure with the bleed screw closed and the coolant level visibily drops in the reservoir tank, then you've got trapped air in the system.

Also check that your thermostat is rated the same temperature as the old. Take it out, put it and the old one into a simmering hot pot of water and see that they open at the same time (presuming your old stat still works right). The temperature should be stamped on the stat itself.