[mgarblik]

I will take a stab at this but may need some additional info from you. When weird situations like this happen, you have to back up to the last time the steering system worked like it should. When was that? What pump was on it and what steering gear was on at the last time it worked correctly? I have never seen a PS pump give you the symptoms you describe that wasn't related to a pump/pulley/belt issue. But it's extremely unlikely you have had 3 defective pumps as well. So if you are sure the belt is staying tight and not slipping, we have to move on. I have also never heard of using any vacuum device to remove air from a steering system including a hydroboost. But lets move ahead. How does the steering wheel feel, engine running, weight on the tires and off the ground? Does it feel normal?, jittery, hard like no assist? Loose and hard when it is squealing? It is possible, but extremely rare that the torsion bar pin in the steering gear is loose or sheared off. This will allow the inner spool of the valve to route high pressure fluid to both sides of the power piston in the steering gear. You should have zero power assist. It should be extremely hard to turn. A pressure gauge might be a helpful tool for diagnosis. It would need to be plumed in the pressure side of the system between pump and gear. Normal pressure should be 60-100 PSI max straight ahead, idling. Through a slow turn of the wheel, weight of the tires on the ground, 300-500 PSI. As you approach the steering stops, 700-1000 PSI Against the stops, 1250+ PSI. The pressure should be very close on a left or right turn. Lets start here and reply when you can.

I forgot to ask if the pulley is a press on design or one with a key drive. Press on pulleys, especially aftermarket ones and rebuilt pumps may not have enough press under load to hold. If it's a press-on, mark the shaft and pulley with a paint marker or liquid paper. Run the engine up to squeal point and see if the marks move. Similar to checking a harmonic balancer for slip.