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Can you vacuum bleed a hydroboost setup?

HankScorpio

HankScorpio

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Having problems bleeding the steering system on my wifes 2001 GMC Safari. I have hydroboost on my '91 V3500 and when I replaced it bleeding was no big deal. This van just wont bleed out all the air. Replaced the power steering pump and found that the hydroboost had been leaking which likely led to the pump failure. Replaced the hydroboost too and now I cant get all the air out. Did some searching here and on the web and have tried lots of methods. Turning wheel lock to lock on jackstands not running. Same thing running. I keep getting foam which then makes it so I have to wait a day to start again. I had to let it sit for about 10 days due to life and when I tried again last night more foam. Can I rig up a vacuum pump to the reservoir and suck the air out? This things driving me nuts.
 
I know you said you turned the wheels with the engine off. But did you do that by turning the steering wheel or manually pushing the wheels back and forth with them off the ground?

One of my colleagues at Workhorse taught me a trick to bleed hydroboost systems many years back. For some reason if the input is coming from the steering wheel it will not bleed right. But if you manually push/pull the wheels to turn the gear the air has a way to get out.

I’m sure he went through the science behind it because he was out service engineer but I’ve lost that detail. But it does work. This I’ve proven personally and at the dealership where my flat rate guys rushed stuff and couldn’t get a system to bleed.

20-30 cycles back and forth is a royal pain to do by hand but it has worked for me.

I’ve never tried putting the system under vacuum to pull the air out.
 
Turning the tires by hand is what worked for me. It seems like the lines above the Hydrobooster would tend to trap bubbles, but cracking those open would only really help if you pressurize the system.
 
I had a Ford once that fought me forever. I remember you absolutely do not touch the brake pedal with it running . Once you shut it off you pump the pedal to release the accumulator pressure to nothing then start it and do the steering side then repeat. If you touch the brakes it gets air trapped in the hydroboost side.
 
Truckman4life said:
I had a Ford once that fought me forever. I remember you absolutely do not touch the brake pedal with it running . Once you shut it off you pump the pedal to release the accumulator pressure to nothing then start it and do the steering side then repeat. If you touch the brakes it gets air trapped in the hydroboost side.
Click to expand...
The Hydroboost does have a spool valve in it that opens and closes ports. You could, as mentioned, try pumping the brakes with the engine off to open and close the ports to move fluid through it.
 
I vacuum fill the power steering system on the r/v bodys(acadia, traverse, enclave). The power steering on them will howl forever if you don't get all the air out.
I use a cooling system vacuum filler that I converted to work with ps. Pull the system down to 25" on vacuum and then suck it full of fluid. Works like a charm.
Something like that would take care of your issue.
 
look up the bleed out step by step . . .

my self and others have posted it before .

wheels off the ground turn and turn no air is huge . otherwise your a dog chasing the tail for ever .

any p/s that foams up = shut down and wait till clear or the foam fluid cuts the pumps life way down . foam dont just come out easy and bleed off .
 
I have not tried turning the wheels by hand without the steering wheel. Will go there next. Thanks guys.
 
Vans in the air. Slowly turning wheels lock to lock by hand without steering wheel. Pausing now and then to let bubbles move. Pump brakes or no? Just touch brakes to release some air? Just moving tires now. Motor off.
 
Also, wtf. Why does it need to be at tires and not steering wheel? I vaguely understand the steering box but I don't get what the difference is. The steering wheel is still turning.
 
Yeah. I knew about he ball bearings, just not their affiliation with Satan.

My K5 is across the shop getting no love because of this damn van!
 
Gm says vacuum bleed it. Got to figure out an adapter for my vacuum pump.
IMG_20220728_210528132.jpg
 
Radiator hose to fuel filter to fuel line to random NPT barb fitting to vacuum pump. This hand pump sucks and my HVAC one is in town.

IMG_20220728_213627265.jpg
 
it could work gene wilder GIF
 
I don't think it matters at the tires or at the wheel. No difference. Just the engine running or not and when to pump the brakes are the things I remember being critical.
 
Vacuum bled system to GM procedure. Still no power steering or brake. Starting to think its a bad reman pump. Don't have a way to check it and the GM diagnostic tool/ pressure gauge is $400 on ebay. This sucks.
 
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