The rubber line wears at the crimp at each end and all it takes is a tiny pinhole to lose pressure. Lots of little pita "work by feel" steps to replacement that will take hours the first time and mere seconds once you know the twist/pull/slide/unclip of things. (A dime can completely lock the gas pedal down. :grrrrr:
I guess I found the problem. Neither the slave or master was leaking but the rubber line between the two sprung a leak. I guess its #10 on this diagram. Is this a BMW part or can I just buy the line at a local parts store.