Brake wont bleed

Post Wed Apr 03, 2013 12:08 am

Hi,Trying to sort the braking on an 89 325is.
Changed the master cylinder,new fluid.But on bleeding i cant even get fuid coming to any of the calipers! its almost as if there is a blockage at the abs pump or somewhere,is this possible?
opened all bleed nipples and pumped brake,nothing.pedel becomes firm and just forces fluid out of the mc res,
Any help apreciated,this is driving me nuts!

Post Wed Apr 03, 2013 12:26 am

are you doing this with the car on or off?

Post Wed Apr 03, 2013 12:30 am

Quaser wrote:are you doing this with the car on or off?

Have tried both,off and with car running.

Post Wed Apr 03, 2013 1:02 am

I wonder if the master cylinder piston has stuck at the end of its stroke, or you've got duff cylinder seals...

Post Wed Apr 03, 2013 1:48 am

davethegoat wrote:I wonder if the master cylinder piston has stuck at the end of its stroke, or you've got duff cylinder seals...

Ive just replaced the master cylinder with a new one,its building pressure in the system through pumping the peddle but no fluid at calipers!
i started to bleed initially in normal way,rr,rl,fr,fl but no fluid coming at any,so opened all to try to evacuate system but still nothing,
Ive been using both an air pressurised bleeding kit up to 50 psi and the old school pump up the peddle method.
Id find it very hard to believe that there is a blockage in any of the lines,is it possible that there is a blockage or airlock at the abs pump?

Post Wed Apr 03, 2013 1:58 am

have you tired bleeding it to the pipes then connecting them up again?

Post Wed Apr 03, 2013 2:17 am

wullie325i wrote:have you tired bleeding it to the pipes then connecting them up again?

Ive bled the master cylinder itself at its outlet,all air expelled from it and its pumping fluid fine out,but its after that the problem is,
seeing as i have no fluid at any caliper the problem must be at the abs pump as its the only thing between ms and all 4 brakes?
Anyone know off hand which are the outlet pipes from the abs pump to the brakes?

Post Wed Apr 03, 2013 12:11 pm

They are marked on the pump, easy enough to trace them too.

Post Sat Apr 06, 2013 6:24 pm

The ABS system works, if I recall correctly, in a way so that when it senses a wheel skidding, and wants to "cut in" it blocks the fluid coming from the master cylinder and then pumps fluid around to the calipers by itshelf, once it senses all wheels are rotating again it opens up again. It's this blocking and unblokcing of the brake line to the ABS block one feels when the ABS operates as the pedal pressure fluctuating. Thus your problem might be because the ABS block is stuck in the position where it blocks the fluid from the master cylinder.