all right heres the story,
i replaced front rotors, pads and rear disks on my 91 Si hatch.
bled the lines and everything was working fine.
this past weekend i replaced the master brake cylinder because the brake pedal would sink to the floor. i got a brand new master cylinder and installed it then bled the system and the pedal drops to the floor. i cant get and pressure.. the vac. valve is working and after i pump the brakes, the pedal doesent get that hard. at least not as hard as it should be. so.. my question, what the **** is wrong with my brakes. how can i see whats wrong. i am now thinking that it could be that the valve is in the wrong way or the booster is giving up.. any thoughts???

 

 

Did u bench bleed that new master cylinder? Check a manual for that procedure if u didnt.

 

bench bleed?? ****. whats that??

 

anyone?

 

Basically its first bleeding the MC outside of the car. Like on your workbench, hence the name. Makes sure you have no air in the system...only fluid, which can happen if you just put in a new MC, fill and bleed at the calipers.

Do a Google search for "bench bleed" there's a bunch of general and model specific writeups.

Check Tyson's suggestion first, its the easier of the two.

 

I went down the same path, and all my problems went away when I replaced the booster. Well, not all my problems...now I'm bending backing plates, but at least I'm generating force.

FYI, I followed the procedure in the service manual Tyson posted and my pedal went to the floor in every situation.

 

cool man thanks for the help