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GM hydro-boost inop

Home > Discussion Forum > Mechanic's Corner - Brakes

Email Author email Ed Kimbrough  Reply to Message reply to message  Post New Message post new message      search forums
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GM hydro-boost inop Ed Kimbrough 7-10-05  
I have a 1994 Thor Pinnacle 34’ P30 chassis 454 ci 4wheel disc brakes VIN1GBKP37N7R. My PS pump growled loudly all the time for about 2 months and now I lose ALL assist on brakes and steering. Also, ps fluid does not leak anyplace but runs over the top of the reservoir when I shut it off. I pulled the pressure control valve out and found no trash but very scored. When I replaced it things worked for a few minutes. Everyone I have talked recommends new factory parts but Delco dealers don’t list a PS pump nor do GM dealers. Now what?
Re: GM hydro-boost inop Pat Hudgins 12-29-05  
What is best source for buying new pump?
Re: GM hydro-boost inop Bob 5-21-08  
I have a 99 Chevy 2500 4x4, 3/4 ton. The hydro booster leaked so I replaced it. From all the info. I've seen on the internet it appears that I did everything right, obviously not. Here's the problem. I can't get any brakes. The pedal goes down real easy and up real hard, I have to pull it up. I've tried a couple different techniques to bleed the system but haven't had any luck. It feels as if the booster does not hit the master cylinder. Help!!!
Re: GM hydro-boost inop Joe Stevenson 1-24-06  
I have a 1980 Chevy/Midas RV with Hydro-boost JB8 10,000 lb. power steering and brake system. In the last 15 plus years of driving and repairing this type system, rebuilding or replacing the master cylinder is like all others only a size larger. The pump (Saganaw type P 1200 to 1300 PSI) is the same on Small and Big Block V8 gasoline engines as well as the 6.2 diesel. I do not know about the larger units. The most likely answer to this problem of noise when the brakes or power steering is applied, or lack of power assist to stop and turn, is a bad pump or restricted hose. You may see your pump at this site http://www.sandstruck.com/catalog/powersteering/powersteeringsaginaw.htm
Also you can test the pressure output of this system with a GM adapter or tool. I have never held it in my hand. A friend told me of seeing one several years ago. In the repair manual it has a #J???? beside it. The pressure hoses internal wall will collapse and prevent adequate fluid from beening supplied. To test this removing each return line, one at a time and start the engine briefly as the system will empty very fast into some type of container when not restricted. The return lines should be rated to hold 250 psi, so a substitute of reenforced clear type hose may help for this test. Please let me know if anyone finds this info beneficial, GOOD Luck and be careful in your work!
Re: GM hydro-boost inop Pat Hudgins 12-29-05  
I have an '83 allegro with gm diesel. Same issues-LOUD growling and overflows at times out reserviour.
I changed to '94 serpentine belt system, does this take reverse rotation pump?
Re: GM hydro-boost inop James 10-2-05  
I too had the same problem with my 91P30 chassis. The exact same syptoms. I took it to the dealer and had the system rebuild with OEM parts. The mechanic had a terrible time bleeding the system. Even with a power bleeder it took 2 days longer than he thought. The bill was $800 but it works great now. That is one I am glad I didnt do myself.

Hope that helps

James
Re: GM hydro-boost inop rich knouse 8-6-05  
Ask your local parts store to check their listings for the diesel engines, PS pumps. All the GM diesels with standard boost brakes (Not air brakes) should use your oil boost type system. Some of the gas use the oil boost, but a lot used vaccum air boost. The pumps for the diesels had been available. rich
Re: GM hydro-boost inop Mark Thomas 8-16-05  
ED,
I have the EXACT same problem. What was the final fix??? I am desperate. Too many valves and switches. Please email me with any info. Thanks
Re: GM hydro-boost inop Pat Hudgins 1-29-06  
Thanks for the part source. My motorhome is a class A allegro. Maybe it takes the 1350-1450 pressure but same flow rate. I am tired of paying people 5-600 dollars and not tell a difference.
Re: GM hydro-boost inop marcus 10-10-05  
I have the hydroboost brakes on my 1984 gmc k25 diesel truck and i just lost all pedal power. The power steering still works and the master cylinder seems ok. Does anybody know how the hydroboost works??
Re: GM hydro-boost inop Doc 1-22-06  
Guys welcome to my world. My pump has groweled and squiller like a stuck pig for 2 years. I started the MH up a week or two ago and when I pressed the brake pedal the pump started sounding like the steering wheel when turned at low speed. I bought a new OEM old stock Power Steering pump (Original GM Part Number 7839810) on the internet. With the 2 lines, one for the steering box, the other goes to the Hydroboost brake booster. That will not be shipped till 1-23-06 I should have it by the end of the week. I bought it with out thinking if it would fit a 454 engine, maybe I will luck out and it will fit all the P30's. Now I'm checking the internet for the Hydroboost Brake Booster. I tried to take a camera and take some pictures of the pump and booster on my MH to see what they looked like, but with no luck. The master cyl. looks like its mounted on top of the frame rail. I hope I end up with the right parts! From looking at
what I seen, I'm going to have to get a skinny little kid to get up in there and change it. There may be a panel under the carpet to see it, never checked that! There may end up being a panel (hole) there when i get done with it. The floor is right on top of the frame rail under your right foot. I have never been able to check the brake fluid.
The MH has always stopped but I didn't tail gate anyone and gave myself plenty of distance between me and anything in front of me. I thought maybe it was just the weight of the MH was why I couldn't lock up the brakes in a panic stop.

I may have to look at this diesel engine deal and see if things interchange.
Re: GM hydro-boost rebuild kit Greg Gastelum 10-13-07  
Have a 1997 c-2500 with break fluid leaking out of hydro-boost.I'm sure all I need is a rebuild kit for it, any idea's where one would be found.
Re: GM hydro-boost inop hamid 10-26-07  
Hi
i have a 1992 ALLEGRO BAY MH. i change the hydro boost, p/s pump, streering box, and valves and it stills growls and the fluid over flows through resivior does anyone have any idea why
Re: GM hydro-boost inop Rick 6-30-06  
My 94 Southwind started growling when I stepped on the brake and shifted into gear, getting louder with more brake pressure or any steering movement. Turned out it was a stopped up vent hose from the power steering reservoir cap. When the cap was loosened while the growling was occurring, the noise was immediately relieved, so we checked the hose and found it to be clogged with road grit. After a little cleaning and relocating away from the wheel well--no more noise! Apparently the clogged hose kept the pump from meeting the demand and caused the pump to cavitate, making the noise I was attributing to a hydrobooster problem.
Re: GM hydro-boost inop DAVID M. MILLER 11-11-07  
I have a 92 pace arrow p-50 chasis, 454 chev. with hydro boost brakes that work off of the power steering pump. The brakes work and the park brake works. The steering went out. I replaced the pump. now the steering works until I put the MH in gear and then you lose the power steering. Don't have a clue about the other components in the system. If anyone has any info, I wil appreciate it. thanks
Re: GM hydro-boost brakes sticking ed jacobsen 9-25-07  
I am working on a 93 allegro bay motorhome with hydro-boost brakes. installed a new booster and still having a problem woth the brakes applying going down the road. any ideas to repair this problem would be helpful. thatk you for your time.
Re: GM hydro-boost inop hamid 10-26-07  
Hi
i have a 1992 ALLEGRO BAY MH. i change the hydro boost, p/s pump, streering box, and valves and it stills growls and the fluid over flows through resivior does anyone have any idea why
Re: GM hydro-boost inop jihn osborne 9-2-07  
I have a GMC Sahara 4.3 v6 day van.
I have rfecently spent a lot of money having it overhauled by a so called expert in the uk only to find that my power steering is now very intermittent unless the vas is rolling. It was never like this before being overhauled but has only occoured since a brake fluid bleed and replacement. If you turn the wheel at rest it turns ok if you then apply brake pressure it goes stiff and difficult to turn. Also there is brake fluid lesaking over the master cylinder from the larger of the reservoirs.
Any suggestions as to where to start looking.
Thanks John Oz
Re: GM hydro-boost inop Ron Kirkland 2-21-07  
I have a 1992 Pace Arrow MH with P series forward control chassis. Power steering pump started growling like the fluid was low and steering was sometimes hard. Fluid was full, so I replaced PS pump. Same problem. Thinking that the new pump was bad, I replaced it again. Same problem. So the problem is not the pump. Now after a few months of inactivity, I have no power steering or brakes. None of these components are accessible, and I am at a loss for how this system works. I would welcome any suggestions.
Re: GM hydro-boost inop bill wright 5-17-07  
Lost my steering and brakes going up mt. eagle in TN. added fluid at the tpp and started working--quit again at the bottom of the MT. drove about 100 miles using muscle power--i don't recomend it. cannot find a leak but fluid level does go down. HELP PLEASE
Re: GM hydro-boost inop clayton karsten 8-19-07  
I'm having the same problem with the whining and stiff steering and brakes, with fluid spraying out of the reservoir overflow when I shut it off. I've replaced the P/S pump and it persists. Please let me know what you discovered, anyone.
Thanks,
Clayton
Re: GM hydro-boost inop mike noble 5-10-06  
Hi, i have the same problems, could you tell me all that was done to fix yours,thank you. mike
Re: GM hydro-boost inop Larry 7-29-07  
I have a very similar problem with a 94 GMC. The brakes and steering both failed after idling for a short period of time the fluid started boiling or blowing out of the reservoir. Did you ever find a cure for your problem?

Thanks for your time.

Larry
Re: GM hydro-boost inop greg young 6-17-07  
My power steering pump makes a laboring noise at high rpm. sounds like pump is starving for fluid. system has also blown three new main pressure hoses. is there any adjustment?
Re: GM hydro-boost inop Jerry Rode 10-3-07  
I have a 1992 Pace Arrow on a P 300 chasiss w/ 4 wheel disk brakes. The brake worked fine but the master cylinder started leaking between master & power boost unit. Paid to have repalced and brakes started to stick, would stop for 5 min. and would free up. Real pain. Search the web A was found that the rubber hose between caliper & frame closes up w/ age. Replaced. Still same problem. Went to my fav. mechanic, he suggest to check the space between booster & master when not screwed tight together. Should be a max of 3 thickness of paper, more won't let the pressure release. It worked. Check yours!???
Re: GM hydro-boost brakes sticking chester dyck 9-27-07  
1981 chev p30 chassis. installed rebuilt hydroboost by cardone. now front brakes lockup while driving. open brake bleeder on front cal and it releases
Re: GM hydro-boost brakes sticking Keith 7-23-08  
Sounds like the Brake calipers may be sticking and not fully releasing; which builds up heat and then the fluid in the caliper expands and applies the brake more. I would check there first and then maybe check the linkage. I have also seen a MH that had an improper linkage which applied the brakes slightly over bumps. And after the heat builds you'll have the same problems.
Re: GM hydro-boost brakes sticking bill wright 3-30-08  
MY BRO IN LAW HAD THE SAME PROBLEM--TURNED OUT HE HAD A COLLAPSED BRAKE HOSE THAT WOULD NOT LET THE FLUID RUN BACK INTO THE LINE WHEN THE PEDAL WAS RELEASED.--SIMPLE FIX,IF THAT IS YOUR PROBLEM--GOOD LUCK.
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