GM Power Steering Pump w/Hydroboost - I Have the Howlz

Hi Everyone I need help - I'm almost to the point of paying an actual mechanic to work on my Safari van!

Recently I replaced the power steering pump on my 2003 GMC Safari because the pump shaft seal was leaking and the shaft had a groove worn in it. Once the new pump was in I began to play the bleed the air game and so far I am losing that game.

My basic symptom is that the van starts the day without any problems and as either time, temperature or #of brake cycles or #of steering cycles increases - then the power steering pump starts howling.

I have learned to do what I call the advanced DIY bleed procedure. This involves a) turning on the motor and pumping the brake pedal firmly for 10-20 cycles, b) turn off motor, c) raise front of van off the ground and with motor off, turn steering wheels lock to lock for a bazillion times.

I've even added my own little improvement - do the above while pulling a 15+ psi vacuum on the power steering reservoir.

I have done all of this at least 6 times. Each time there is a slight increase in how long the pump stays quiet before the howling returns. I can now drive the van for 20 miles of mixed hiway/streets before the howlz begin.

FWIW - there are no fluid leaks. When I pull a vacuum on the reservoir, it stays holding a vacuum all night. It also holds a vacuum while I do my brake pedal pumping and steering wheel turning.

So I'm stumped and would welcome any ideas or advice. Thanks!

I did the pump on the wife's 1997 Safari last year. The replacement pump makes more noise than the old one did before it failed. I just pretend it's supercharger whine. 

Is it making noise because it is low on fluid. Do you loose power assist for the steering/brakes when it starts making noise? I don't recall ever having problems with bleeding hydroboost

Pump was rebuilt by installing a new Chinese shaft seal and applying a coat of paint.

They are all trash.

Call Power Steering Products in Houston. 713 681-1446 They rebuild pumps, racks, gear boxes, and that old 60-70's power steering system that had the actuator with the tie rod on it.

My guess is you're sucking air in.