Brake weirdness

[lujaman]

Greetings, hopefully someone can help,here goes.
Some months ago I started getting the brake pedal travelling nearly all the way to the floor when the van was first started, couple of pumps brake solid and good again it seemed to slowly get worse so bought a new mc fitted that still have the same issue. Invested in a vac bleeder thinking it was air somewhere, same issue. Was advised to change the servo couldnt understand how the servo would be affecting that but changed for a good 2nd hand one with different mc still attached, same issue. Have adjusted up the rear brakes correctly then bled with a positive bleeder attached to the resvoir, same issue. Then changed the brake bias valve, checked rears adjusted ok again, bled again, same issue.
So iam currently starting up with engine in idle brakes sometimes good sometimes soft all the way to floor, if I go for a drive the pedal remains good until I come to a stop or reverse then it goes all the way to the floor again.
mc was bench bled and its had about 10l of brake fluid through it trying all number of ways to bleed it.
Any advise much appreciated,
Cheers
Luke

1.9 DG early wbx.

[Mr Bean]

Can't quite remember the exact chain of command but one thing often not considered is the brake pedal or some related component failing to return all the way so you randomly do not get a full bite at the fluid. so to speak.
CS

[Oldiebut goodie]

My thoughts would be to check the servo vacuum hosing for leaks/bad connections.

[Ian Hulley]

Have you fitted a new brake master cylinder ? To me it would imply the seals are failing ... ours went suddenly (and at home) in between journeys fortunately so no dramas. The brake fluid in the reservoir had suddenly gone black and gungey and I ended up changing the clutch m/c as well (don't ask ) I recently changed the clutch slave cylinder as preventative maintenance as the engine and box were out and the same black gunge was in that as well and took some clearing through.

Ian