Hydroboost help?

[BarbeeT]

Hi all... We changed the hydroboost on the GN because it was leaking. Now when we put on the brakes, they go to the floor. Can't even hold the car still while doing a brake torque... any ideas on whats happening. We did all the instructions that came with the hydroboost, you know bleeding and all that but, still not right, still cant hold the car in place? HELP???

 

[Jerryl]

Hi all... We changed the hydroboost on the GN because it was leaking. Now when we put on the brakes, they go to the floor. Can't even hold the car still while doing a brake torque... any ideas on whats happening. We did all the instructions that came with the hydroboost, you know bleeding and all that but, still not right, still cant hold the car in place?

Was the brake pedal ok before the change?
Most lilkely it is the master cylinder leaking internally or still air in the brake system.

The Hydroboost is only a "power assist", so without it, the brake should be hard to press down, indicating pressure buildup.

 

[BarbeeT]

Hydroboost

Before we changed the hydroboost, it leaked, thats what caused us to get another one. Before that the brakes were fine. We had replaced the master cylinder about a year ago, no reason, just started replacing parts as we found them. Could it still be the master cylinder, even tho we changed that last year?

 

[my85grandnation]

I would reblead the brakes and make sure there is no air in the lines at all. How did you bleed them? Sometimes if you are bleeding them and you just open the valve on the brakes and start pumping it to get the fluid to come out everytime you let up if the valve is open air can get sucked back in. What I like to do to prevent this is to place a piece of clear hose over the bleeder valve and hook it onto a catch bottle to catch all the fluid. Next I open the valve and have a buddy press the brake pedal down slowly and have him hold it down so fluid is still flowing out, and while the fluid is still flowing I close the valve and then have him let off the pedal that way when he lets off no air can get sucked back up in there. I do this open/close method several times on each wheel till Im sure there is no more air in the line. Just make sure you always keep enough fluid in your master cylinder or it will suck air and you will have to start all over again. HTH

 

[cool 84]

You've got to bench blead the master if you emptied it or removed the brake lines.

 

[84GNGary]

You've got to bench blead the master if you emptied it or removed the brake lines.

Yup.
It maybe too late now but you do not have to remove any of the brake lines to replace the hydrobooster. Just unbolt the master cylinder from the HB and gently move it over a little.