Brake pedal sink

[Wh33lhop]

Alright, I want to solve this once and for all. This seemed to happen after I swapped boosters and master cyls to an E32 setup for the swap.

Basically whenever I press the brakes the pedal will slowly sink down about an inch and then get solid. I've just replaced all 6 lines with SS and bled the brakes with some Superblue. Still does it.

Basically it seems to be narrowed down to the master cyl or ABS (which is inop) and possibly a secondary problem with the booster as well. Could this be air trapped in the ABS somewhere or is it definitely a master cylinder problem?

[White325is]

Sounds like a master cylinder to me. I had this same problem and just swapped mine out. all gone. Sometimes it will drop a inch or so and every so often, maybe 1 time every two weeks it would go right to the floor.

[Ceeker]

yeah...most probably a master cyl on it's way out. I wouldn't worry bout it until it gets more frequent. Unless it's really bugging you.

[Wh33lhop]

Pedal sinks down an inch every time unless I pump the brakes.

Thanks guys. Anyone know where I can get a rebuilt or used good condition E32 master?

[nando]

Its probably just air, mine did the same thing. Replacing the mc didn't fix it. Try tapping on the calipers with a hammer while you bleed, frees up trapped bubbles. Thats what i think ended up finally fixed mine.

[Wh33lhop]

Hm. I also didn't bench bleed my master, I may try that first plus a rebleed a la nando before splurging on a new MC.

[MR 325]

Unless your master was new there is no need to bench bleed. I would however recommend bleeding the master at its lines. Have somebody pump and hold the brakes and crack the lines just like you would a caliper bleeder. Then bleed calipers again.