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Discussion Starter #1
Just replaced all of these at once (along with steering gear and all suspension and steering links, joints, and bushings. I bled the air out of the system as detailed in one of the threads here. I had the interior and dash out at the time for another project so I did not drive the truck. I just filled the system and bled it. It seemed to go left and right nicely without binding or difficulty. Brake pedal felt good as well.
A month later I get interior work completed and start the truck up again. Steering is no longer power assisted to say the least. I did as some other threads suggested and put the front back up on jackstands, revved engine to high RPM and manipulated wheel left and right, also pushed brake pedal to the floor a few times. Seemed to work again. Not sure why. Put it back on the ground and took it for a short drive and back to the drawing board. Still occasionally very difficult to turn wheel. Also no power assist to brakes when that happens. A big rev of the engine will get things working again. Sometimes for a second or two, other times for slightly longer. All parts are under a warranty, but not my labor and I hate to put new parts
on and find out it was not what I needed. Any ideas what could be going wrong here? Bad pump? Pump does seem to do something so ? ? ? Zero bubbles in fluid. Bad Hydoboost?
 

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Sticking flow control valve on the back of the PS pump.
Usually comes with the pump. Easily changed without changing whole pump, but, if it's a recent pump, exchange it.
 

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Discussion Starter #3
Thanks. Going to replace the pump tomorrow.
 

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Discussion Starter #4
Would replacing the flow control valve be easier than swapping out the pump? And how would I know which flow control valve to put in there ?
 

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Discussion Starter #6
Well, replaced the hydroboost again last night with no improvement. Replaced pump today and have a very slight improvement but still highly dangerous and random power steering and brakes. I'm just about to light this truck on fire. Is there anything in the new steering gear, a valve or anything that could cause this? I did check the opening in the flow control valve and it was right at 5/32nds which is what it should be stock. I never had trouble with my stock pump. Should have just kept it.
 

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Discussion Starter #7
No foam, no noise, no bubbles. Fluid is fairly still. I'll go through the full bleeding procedure one more time and see what happens. If that doesn't work I'm going to look into aftermarket pressure valves or something. To say I'm frustrated is the understatement of the year.
 

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Discussion Starter #8
Seems to be slowly sorting itself out. Steering seems much better. Still a bit under-boosted when idling at a standstill, and brake pedal seems a little low, but it hasn't surprised me with zero brake boost and zero power steering all of the sudden for awhile now. I did some careful re-bleeding of the system. Front end up, brake pump slowly 8-10 times and then full left and full right a few times, rinse, repeat. So far so good.
 

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Seems to be slowly sorting itself out. Steering seems much better. Still a bit under-boosted when idling at a standstill, and brake pedal seems a little low, but it hasn't surprised me with zero brake boost and zero power steering all of the sudden for awhile now. I did some careful re-bleeding of the system. Front end up, brake pump slowly 8-10 times and then full left and full right a few times, rinse, repeat. So far so good.
Great news, so far!

(y)
 

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Just replaced all of these at once (along with steering gear and all suspension and steering links, joints, and bushings. I bled the air out of the system as detailed in one of the threads here. I had the interior and dash out at the time for another project so I did not drive the truck. I just filled the system and bled it. It seemed to go left and right nicely without binding or difficulty. Brake pedal felt good as well.
A month later I get interior work completed and start the truck up again. Steering is no longer power assisted to say the least. I did as some other threads suggested and put the front back up on jackstands, revved engine to high RPM and manipulated wheel left and right, also pushed brake pedal to the floor a few times. Seemed to work again. Not sure why. Put it back on the ground and took it for a short drive and back to the drawing board. Still occasionally very difficult to turn wheel. Also no power assist to brakes when that happens. A big rev of the engine will get things working again. Sometimes for a second or two, other times for slightly longer. All parts are under a warranty, but not my labor and I hate to put new parts
on and find out it was not what I needed. Any ideas what could be going wrong here? Bad pump? Pump does seem to do something so ? ? ? Zero bubbles in fluid. Bad Hydoboost?
Just replaced all of these at once (along with steering gear and all suspension and steering links, joints, and bushings. I bled the air out of the system as detailed in one of the threads here. I had the interior and dash out at the time for another project so I did not drive the truck. I just filled the system and bled it. It seemed to go left and right nicely without binding or difficulty. Brake pedal felt good as well.
A month later I get interior work completed and start the truck up again. Steering is no longer power assisted to say the least. I did as some other threads suggested and put the front back up on jackstands, revved engine to high RPM and manipulated wheel left and right, also pushed brake pedal to the floor a few times. Seemed to work again. Not sure why. Put it back on the ground and took it for a short drive and back to the drawing board. Still occasionally very difficult to turn wheel. Also no power assist to brakes when that happens. A big rev of the engine will get things working again. Sometimes for a second or two, other times for slightly longer. All parts are under a warranty, but not my labor and I hate to put new parts
on and find out it was not what I needed. Any ideas what could be going wrong here? Bad pump? Pump does seem to do something so ? ? ? Zero bubbles in fluid. Bad Hydoboost?
Sorry to bring up old post. I seemed to have the same issue. Mine started with low brake pedal. I noticed my brake booster was leaking. Replaced, no fix. Replaced master cylinder, no fix, replaced ps pump and hoses, no fix. Replaced rear calipers, now starting to get better but pedal still super low. In the process I bleed the lines dozens of times to get all of fluid out. Went through at least 3 of the large bottles of STP brake fluid. My pump always sounds empty no matter how much fluid. I try to fill just enough to stop the wine. Then randomly spits out the fluid out of the fill cap after sitting for a short time. Also bleed the ps fluid and still the ps pump wines as if its empty. I still dont feel I have the braking power. I've also replaced all the pads as a mechanic suggested my calipers we over extending. No change. Took it to a shop, told them I would pay for their time for professional opinion. They suggested complete brakes system overhaul. They said my rear drum/rotor were totally worn. Well after buying all the parts, my original drum/rotors were thicker than the high end replacements. Running out of patience and money. I've read about the flow valve on the ps pump. My pump was new from NAPA and the flow valve has paint inspection mark. Shale I replace the pump or get a flow valve?
 

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Discussion Starter #11
I'm about as lost as you are. I'm still not pleased with all of the work I put in. My brake system itself seems fine and I don't think that's the problem. The hydroboost is new (twice) and the power steering / boost pump is new (twice). Also brand new steering gear. Still have a low brake pedal and if I'm sitting at idle I can just push it to the floor. Power steering doesn't surprise me with the occasional zero boost while driving along but it still is very under-boosted when sitting still at idle and trying to jockey into a parking spot. Nothing leaks, which is nice, but I'd really like it if it worked right too. I'd consider changing out the orifice / valve on the back of the boost pump but don't really have any idea what size to buy or how to go about that program. I should have just taken the one off my original, factory boost pump but that ship has sailed as it was returned for core two pumps ago. I'm only running 285's on the truck so I'm not exactly running huge tires and I never had any boost issues until I changed out the original pump and original hydroboost (and original steering gear if that could possibly have anything to do with it). I hate to go pay for a diagnosis and have them tell me I need to redo my brake system, because I know that's not what I need to do.
 
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I'm about as lost as you are. I'm still not pleased with all of the work I put in. My brake system itself seems fine and I don't think that's the problem. The hydroboost is new (twice) and the power steering / boost pump is new (twice). Also brand new steering gear. Still have a low brake pedal and if I'm sitting at idle I can just push it to the floor. Power steering doesn't surprise me with the occasional zero boost while driving along but it still is very under-boosted when sitting still at idle and trying to jockey into a parking spot. Nothing leaks, which is nice, but I'd really like it if it worked right too. I'd consider changing out the orifice / valve on the back of the boost pump but don't really have any idea what size to buy or how to go about that program. I should have just taken the one off my original, factory boost pump but that ship has sailed as it was returned for core two pumps ago. I'm only running 285's on the truck so I'm not exactly running huge tires and I never had any boost issues until I changed out the original pump and original hydroboost (and original steering gear if that could possibly have anything to do with it). I hate to go pay for a diagnosis and have them tell me I need to redo my brake system, because I know that's not what I need to do.
Went to local auto parts and they could not even bring up the flow valve on the ps pump. Dealer item he says but can be found on ebay. Amazon, jegs, etc...like you I'm frustrated as hell.
 

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Discussion Starter #13
What year is your truck dube-dmax? You just have a single pump running your hydroboost and your power steering, correct? Not sure I understand what a rear drum/rotor is unless you're talking about your parking brake.
 

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Discussion Starter #14
Never mind. Read your signature . . . Same year / drivetrain as mine but dually.
 

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Are the hoses running to the hydro boost and steering box all replaced? Any crush or kinks? Did you all remember to remove that stopper you used to keep PS fluid off the floor?
 

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Discussion Starter #16
Not sure what stopper you would be talking about but the plastic plugs on the new pump and hydroboost were of course removed before assembly. Rubber return hoses are not new but seem fine. No bends or kinks in metal / rubber high pressure hoses. Pretty sure I need to mess around with the valve / orifice on the back of my replacement pump. Either replace it or drill it out :) .
 

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Yea, the dually rotors are combination drums for the ebrake. I sure hated that job. Seals alone were $150 Just watched a video on it about bleeding. I did this but only did one or two times. This guy said it could take dozens of times. Currently replacing my water pump, so when that is done to try the bleeding trick x 24
 
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The upgraded valve for the power steering pump is gm part # 26095470.

If you Google it, you'll find both a plethora of retailers, and, the bulletin that produced it.
 
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Not sure what stopper you would be talking about but the plastic plugs on the new pump and hydroboost were of course removed before assembly. Rubber return hoses are not new but seem fine. No bends or kinks in metal / rubber high pressure hoses. Pretty sure I need to mess around with the valve / orifice on the back of my replacement pump. Either replace it or drill it out :) .
Sounds good.

The stopper would be one of those color coded plugs we use to seal dripping hoses..Mostly I was kidding but it actually happened at work to one of the techs recently. Entirely forgot about the stopper he used and put it back together. Stopper was discovered by me following overheat during road test and removal of hoses to recheck (coolant) flow to a hybrid inverter in this case. Pretty unusual, but it happened.
 
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Discussion Starter #20
The upgraded valve for the power steering pump is gm part # 26095470.

If you Google it, you'll find both a plethora of retailers, and, the bulletin that produced it.
So I gave it a Google, found the part, ordered it and received it. I pulled the power steering pump last night and installed the new valve. The old one looked exactly the same but hey, I'm still putting the new one in. While I had the fender liner off I noticed that my hydroboost (second replacement one) was leaking . . . I put the power steering pump and all back together last night. I went ahead and removed the hydroboost last night and replaced that with a new one this morning. I dotted all of the I's and crossed all of the t's on the bleeding procedure. Brake pedal feels MUCH better. Unfortunately, power steering is back to just awful. EXTREMELY under boosted at idle. All new GM power steering fluid. Bled as properly as I could. Zero foam. Zero grinding or humming noise. I just have to rev the engine like crazy in neutral to turn the wheel lock to lock while stationary and very difficult to turn the wheel while moving slowly at idle as well. 285/75/16 tires so slightly oversize but nothing extreme.

I'm just lost at this point.
 
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