Coolant Air pocket

How to test if the heater core is good on a ford Aerostar 97 ?

On my 97 Escort there is no bleed valve for air pockets. After flushing it, I ran it on water with the cap off and it got rid of the air pocket through the filler neck on the radiator. Then I drained half the water out and filled it with anti-freeze. Does anyone know about air pockets and a better way to do this?

I've used my pressure tester and put a few psi on the system this seems to help somewhat.
I've also jacked up the front of the car and this seemed to help.

Pull off the supply-side heater hose while the vehicle is running at normal temperature and the heater set to heating, to let the air out.
Willie