So, I was replacing the front heater core since the dash was off and I
figured it probably hadn't been done.

I got to wondering how air is supposed to get forced out of the core when
it's higher than any other point in the system including the radiator bleed
screw.  Is it just from pressure from the water pump forcing the air bubble
out of the core and that bubble bleeding through one of the other holes?

[There is a little background to this question that I'll follow up with,
but I want to let out the profoundness of my ignorance in stages so it's
less shocking.  My van is an 85 Westy manual (formerly AT) bostig.]

mike