Symptoms of a failing hydroboost brake system?

[my85grandnation]

I just went and had the brakes redone on my 85 GN they needed everything since somone had put an oil based substance in the master cylinder and it ate away the rubber hoses and everything else in the system that was rubber and then gunked everything up from the calipers to the master cylinder. The only thing that wasnt replaced was the hydroboost system because it seemed to work fine. When I was leaving the brake place the peddle seemed a little hard but not bad, when I stoped at a red light everything seemed normal but when I went to start up the pedal wouldnt come up. It stayed down. I had to reach down and pull it up. I took the car right back to the brake place and had them start looking it over. They said the power steering fluid was a bit low and that theyed check everything else out again. My main question is does anyone here think that the hydroboost system is failing now or was it just cause the power steering fluid was a bit low?

 

[turbo2nr]

Even a brand new PowerMaster could fail as you leave the garage. So be ready for no brakes at any time. Practice the "Oh Chit, where's the parking brake?" often.
power steering and the brake system have only one thing in common, they are both under the hood.

Your brake system had something wrong with it, for sure. Could have been low on fluid, a leak?

 

[my85grandnation]

Well see this is not a powermaster system its the hydroboost system that came before the powermaster, which the hydroboost is usually a reliable unit just needs rebuilding every once and a while.

 

[my85grandnation]

Another question I have is, can the power steering fluid that runs the hydroboost somehow work its way into the master cylinder thus contaminating the brake fluid? If it can then that may explain why there seemed to be some kind of oil in the brake system.

 

[TurboDave]

Even a brand new PowerMaster could fail as you leave the garage. So be ready for no brakes at any time. Practice the "Oh Chit, where's the parking brake?" often.
power steering and the brake system have only one thing in common, they are both under the hood.

Your brake system had something wrong with it, for sure. Could have been low on fluid, a leak?

You'd better read up and study on Hydroboost systems. They use power steering fluid pressure as their "power boosting" agent. Sorta like vacuum brakes use vacuum and powermasters use high pressure air, etc.

 

[TurboDave]

Another question I have is, can the power steering fluid that runs the hydroboost somehow work its way into the master cylinder thus contaminating the brake fluid? If it can then that may explain why there seemed to be some kind of oil in the brake system.

I suspect it's possible, if some internal seals let go, but I've never heard of it.
There are litterally hundreds of thousands of hydroboost systems in use today on virtually all Ford and Chevy turbo diesel trucks...

Your master cylinder likely needs a rebuild.

 

[turbo2nr]

You'd better read up and study on Hydroboost systems. They use power steering fluid pressure as their "power boosting" agent. Sorta like vacuum brakes use vacuum and powermasters use high pressure air, etc.

Sorry, 11:00 on a fri night. I didn't even read the question right. I know nothing about the Hydroboost.

 

[my85grandnation]

Well I had a brand new master cylinder put on it and when I was leaving the place after all work was done the pedal stayed in the down position when held there for a bit at the stop light so I am trying to figure out what caused that to happen like that?

 

[84GNGary]

The power steering fluid and the brake fluid cannot mix internally if something goes wrong with either unit. They are two independent circuits and for that to happen would require seals in both units to fail at the same time. All the hydrobooster is , is a hydraulic ram that pushes against the master cylinder when you apply the brakes. You would definately notice the hydrobooster leaking and a spot of the floor. Also the different fluids cannot be mixed either and each will damage seals in the other system. As far as the oily substance in the fluid unlsee someone put the wrong fluid in there. Maybe not a bad idea to flush the brake and power steering systems out and replace with the proper fluid.

I just replace my hydrobooster over the summer due to it leaking. Its not too bad except working under the dashboard. I got it at Advanced Auto for $160.00 w/ lifetime warranty.
Here is some info from the shop manuals, hope it helps.

 

[my85grandnation]

Well figured out why my pedal stayed on the floor. I got my car back today and the brake place didnt get the rear lines tight enough so it leaked and got air in the lines. As for how the oily substance got in there in the first place it is a big mystery still?