Power steering/hydroboost problem

[Theman85GN]

I'm trying to determine the correct hydraulic psi a brake hydrobooster requires
along with the power steering pump psi output.
I recently installed a reman'd hydrobooster and have read every trouble shooting info out there and still having problems. It seems the brake booster
is providing very little assist @ idle but when you increase rpm,s say to 1800 to 2000 in park the brake pedal gets harder and is providing much more assist. In talking with my local mechanic he thinks its probably a bad booster
although it is providing some assist unless there is weak power steering pump output. The steering itself seems fine..
So the question is... What is the factory power steering pump output pressure and the required minimum hydrobooster pressure to function properly.
By the way I do know how good the original hydroboost brakes work because they are awesome except for the fact it was leaking at the firewall hence the replacement. Any input who guys can provide is greatly appreciated.
I hate to remove/return/reinstall the hydrobooster only to find out that was not the problem.

[Theman85GN]

Any one have any ideas or input ?

[kenmosher]

No direct help, but maybe this will get you some info? (Only hydroboost vehicle I ever had was a beater Eldorado diesel).

http://www.gmhightechperformance.com...raking_system/

http://powerbrakeservice.net

I've got a service manual set for the 84-85s, but I haven't had time to look through them yet.

[Theman85GN]

Ken,
Thanks for the info, I will read that article again.
Any specific info you can find regarding psi requirements in the service manual
would be greatly appreciated.
I'm thinking about buying a brake psi gauge and a power steering test kit
but I'm not sure what the results will tell me with out knowing what they should be.
Thanks again

[Keller]

From what I have read PS line pressures can be in the 800-1100 PSI range on the high pressure side, and 3-7 PSI on the return side.

BTW, the history of Hydroboost goes all the way back to 1973 when it was invented by Bendix, and has long been used from the factory on diesel trucks and other cars that are expected to have low manifold vacuum. Even the Hummers and some Ford Cobra Mustangs. All of the "big three" manufacturers have used in in diesel trucks.

You may also find data on diesel truck sites and forums.

[TexasT]

You don't say if you have "burped" the air out of the system.
You don't say if you have enough fluid in the system.
With the engine running and the front tires off the ground you should turn the steering wheel lock to lock several(at least three) times to get the power steering part "burped". You should be watching the reservoir to keep it topped off. Then you can cycle the peddle several times to get the brake part "burped".

Then if you removed the master cylinder you can bleed the brake system to get the air out of it.
When you are turning the steering and cycling the brake pedal you should be seeing the fluid return to the reservoir. If it has air bubbles you need more burping to get the air out. heck your return line for kinks/restrictions if the fluid isn't flowing back into the reservoir.