if you have an air pocket in the cooling system still you'll overheat, just turn the heater on and when its hot you should be fine there.
check your radiator though for cold spots, or a collapsed hose
go get a cooling system pressure tester, you can rent one, basically it goes in place of the radiator cap and you use this vacuum pump with a gauge , pressurize the system to 15 psi ( do not go over 15 psi) if the system holds at 15 psi then your ok, if it drops you have a leak in the system... do this test with the engine off of course
