Power steering help.

Pretty much have no power steering. Thinking it probably has air in the system, but I can't get it out.

Put the front end on stands and turned the wheels from lock to lock about a thousand times, trying to work the air out. Let it down to the ground and nothing. Still hard as heck to turn.

Bought a new pump. Went through the same process with it. Still nothing.

Something I noticed, When i leave the cap off and cut the engine off, fluid bubbles and runs out of the reservoir.

78 f150
What do you think?

I've never had one air lock, However, You can crack the flair on the box and see if the fluid leaks out when you turn. I've had a box fail though. Lost power steering to the right, but had power steering to the left.. or vise versa.... that was on a 91...... pumps are the same though.

sounds like the box is bad, had one do the same thing several years back.

BAD steering gear box!

Dang! I was afraid of that. Is the centering valve likely to be the problem? Can I fix that myself?