Car is 04 r53 , manual , full bolt ons , r56 S brakes , ss brake lines...
So I been fighting a sinking brake pedal and I've bled the brakes multiple times , used the scwaben scan tool to bleed abs module and replaced the brake master.
the issue is my brakes seem to be hanging up and my brake pedal slowly sinks to the floor as I attempt to hold the brake like if I were at a stop. I unhooked the vacuum line from the booster and vacuum / smoke tested it AND it leaks into the cabin by the brake pedal where its plunger goes into the brake booster.. does this mean the boost has a bad seal ???
any help would he appreciappreciated because I need this fixed asap so I can get the clutch job going and race this sucka this summer..

 

Help I replace the brake booster the brake master I've bled the car about 10 times altogether now using the schwab and tool activating the ABS and everything and it still has a sinking brake pedal to the floor once it started WTF am I missing there are no leaks anywhere the system holds 15PSI once I pressurize it and it'll stay that way as long as I let it sit what is going on ?????

 

Up front; never bled the brake side just the clutch slave but using a power bleeder similar to yours. Bumping hopefully to generate more discussion / input.

would guess the issue is in the master, internally, perhaps defective right out of the box; it happens as we all know.

Anything unusual noticed / difficulties during bench bleeding?

 

I can't imagine both masters and both brake boosters eother or being bad and exhibiting the same exact symptom and same exact amount of pedal drop..
I've bled the calipers a total of over 20x ****ing times amd an entire bottle for each caliper befor going to the next , refilling , repumping and doing it again.
I'd also start the car after all 4x calipers were bled to test the pedal only for it to feel the exact same every ****ing time.
I put on a replacement AND TESAND 1ST brake booster alomg with a brake master , ive inspected EVERYTHING and THERES NOOOO LEAKS .
When I pump the pedal it gets pressure and as I hold it, it slowly sinks allllllllll the way to the floor..
we even used the schwaben tool MULTIPLE times once again activating the abs module..
I also have stainless flex lines too so they're not weaping or dry rotted , front r56 s calipers are relatively new... I just don't get it

 

Maybe a bad valve in the ABS module or whatever it’s called? I know it can happen with some vehicles - not sure if it also applies to Minis.

I haven’t had a reason to really mess with ABS since my Audi doesn’t have it, and my van doesn’t even have power brakes.

 

guessing drums at all four corners too; two metric tons of white knuckle fun on wet pavement...

 

Yep. Four-wheel drums, though it really isn't too bad apart from a slight pull to the right; it weighs about the same as a modern Accord. I probably need to replace the inner and outer RF wheel bearings before I mess with the brake adjustments any more, but that'll have to wait until I re-loom the engine bay harness.

 

So I left my brake pedal depressed over night , then I bled it 2x more times.. the pedal still sunk to the floor... so I said F it and went to pull my car out so I could paint in my garage and for some reason the brake pedal held. Though it was verrrrry close to the floor , it held.. so I took it around the block romping on the brakes and it seemed to get better gradually.
so after a few blocks I took it back home and bled another 2x times and went for another test drive , I ended up driving like 20miles or so and the brake pedal now feels 100x better.
it still feels like it travels abit too far befor it bites good but it's atleast fully drivable and my calipers no longer hangup either..
what a pita.
I think I HAD to drive my car inorder to push the air down far enough to be bled out..I have a feeling its was just bleeding rite by the air somehow..
now onto my clutch job..