air in coolong system

I recently installed a new thermostat. Now, it seems I have air in my cooling system that I can't get rid of. I can hear the air pockets gurgle, and when they pass thru the water pump. It will also spit a small amount from the overflow, until the thermostat opens. (I may have overfilled after the 'stat install).

side note- there are no adverse symptoms when the car reaches operating temp.

This leads me to 2 questions;

1) How do I remove the air from the system?

2) Why does my car seem to run cooler (although it doesn't overheat) without the thermostat? (I discovered it didn't have one installed when I went to replace it.)

thanks in advance!!