GM Hydroboost question

Ok, I replaced the power steering pump on my buddies 97 GMC Astro Sunday. Now I can't seem to get it to bleed. I let it idle for a little while, drove it around about 15 miles around town and 20 on the highway (including some figure 8's in a parking lot). At idle there seems to be no steering assist but when you raise the revs up, even sitting still, there's boost. He was in a hurry to get the van home so I told him that maybe driving it will get the air out, though there's no tell tale whine or groan like there is air in there.
That didn't work. I called him today and there's no change. Is there a way to bleed that system, does it even need to be bled? It looks like the whole thing (pump, brake booster and gear box) are in series and there is a rubber hose from the brake booster up to the reservior so it should self bleed?
Any experience or ideas?

should bleed itself. why did you replace the hose, did it leak? maybe it leaked all the fluid out before and boned something up?

A lot of them are set up with with a dual high pressure outlets, single low pressure return. Belt tension, worn pump, clogged outlet??? How are the brakes - taking more effort to stop than usual? Usually a failure of the h-boost - typically seals - it wouldn't really have an effect on the steering. For bleeding - front wheels off the ground and cycle steering lock to lock a bunch - 10-15 cycles to bleed.

Ok, here's the deal. When I got the van it had no boost, steering or brakes. When removing the pump the pump shaft came right out so the pump failed internally (170K on the clock). I put a new pump on, nothing else was replaced. After it was done I started the van and turned the wheel side to side a few times and all felt fine but the van was in the air at the time. I backed it out of the garage and the brakes felt fine. My buddy got in and said there was no boost.
Then I tried driving it around and everything and there's only boost while the engine is at high idle. On the back of the pump there is a sensor that goes around a metal rod that sticks out of the back of the pump. I assume it's a temp sensor since it's not a wet area, no seals and no fluid present (immagine a coolant temp sensor). I wonder of there is a pressure regulator that is bad or something, but I think that's internal to the pump.
Oh, and the brakes seem just fine.

If the brakes have boost (pedal might sink a little on start up). I would start suspecting the steering box internals?? - any external leaks at the box housing? Usual suspects are blown seals and worn bearings. Box rebuild kits are in the $50-60 range.

jack up the front of the van enough to get the wheels off the ground and do about 20 full sweeps lock to lock with the engine off.

novaderrik wrote: jack up the front of the van enough to get the wheels off the ground and do about 20 full sweeps lock to lock with the engine off.

I'm getting the van back tomorrow. I was thinking about doing that. Why do you recommend it, have you run into this before?
Typical GM, something that should be simple is more complex than it has to be cuz they always want to reinvent the wheel and their engineers suck.
[rant over]

DrBoost wrote: Ok, I replaced the power steering pump on my buddies 97 GMC Astro Sunday. Now I can't seem to get it to bleed. I let it idle for a little while, drove it around about 15 miles around town and 20 on the highway (including some figure 8's in a parking lot). At idle there seems to be no steering assist but when you raise the revs up, even sitting still, there's boost. He was in a hurry to get the van home so I told him that maybe driving it will get the air out, though there's no tell tale whine or groan like there is air in there.

Does it have a little connector on the back, on a dongus-thingy that the pressure line threads into?

If so, pull the dongus-thingy off and make sure that its O-ring is in the correct groove. There's two grooves, one of which has a tiny bleed hole. Dollars to donuts, the O-ring is in that groove and not the correct one.

Quick check - unplug the solenoid and see if assist comes back. What that thing is, is a variable orifice. It's kinda neat, it uses an electromagnet mounted externally so that it can't leak fluid.

DrBoost wrote:

novaderrik wrote: jack up the front of the van enough to get the wheels off the ground and do about 20 full sweeps lock to lock with the engine off.

I'm getting the van back tomorrow. I was thinking about doing that. Why do you recommend it, have you run into this before? Typical GM, something that should be simple is more complex than it has to be cuz they always want to reinvent the wheel and their engineers suck. [rant over]

That is what I do to ALL power steering pump replacements, altho I only do about 5-8, maybe 10, full lock to lock turns. I then start it up and do some more lock to lock turns with the wheels still in the air. In addition, since it has hydroboost, depress the brake pedal 10 times after bleeding the pump. Oh and always leave the cap off while bleeding.

Maybe I have worked on too many of the domestics, but I can't stand furrin cars, except Mazdas for some odd reason. Those are the cars that make no sense to me.

Brian

Knurled wrote:

DrBoost wrote: Ok, I replaced the power steering pump on my buddies 97 GMC Astro Sunday. Now I can't seem to get it to bleed. I let it idle for a little while, drove it around about 15 miles around town and 20 on the highway (including some figure 8's in a parking lot). At idle there seems to be no steering assist but when you raise the revs up, even sitting still, there's boost. He was in a hurry to get the van home so I told him that maybe driving it will get the air out, though there's no tell tale whine or groan like there is air in there.

Does it have a little connector on the back, on a dongus-thingy that the pressure line threads into? If so, pull the dongus-thingy off and make sure that its O-ring is in the correct groove. There's two grooves, one of which has a tiny bleed hole. Dollars to donuts, the O-ring is in that groove and not the correct one. Quick check - unplug the solenoid and see if assist comes back. What that thing is, is a variable orifice. It's kinda neat, it uses an electromagnet mounted externally so that it can't leak fluid.

I think you hit the skater the knee there! I'll check that first.