Mk 5 Brake Problem Help ?

[Van Winkle]

Hi , need to pick some ones brains on this one.
Set off out and brakes all normal, then after short trip noticed brake pedal going nearly to floor but brakes still stopping the van.
Checked servo today as per Haynes manual, seems ok, with engine off can get a firm pedal when pumped. Start engine and pedal go nearly to floor but does not hit the end of travel.
Checked fluid and no loss of fluid anywhere, jacked front up checked calipers and both fine and pads ok , wife pressed pedal and bugger all happens ( had a look and she pressing clutch !!! @$&% Well I don't drive how do I know which is which ! )
Wife presses correct pedal and both front wheels lock up ok, lower front and jack up rear, wife presses correct pedal again......bugger all on both back wheels.
whipped wheels off , cylinders look ok , no fluid coming out anywhere.
Compensation valve working ok and arm all free and moving.
Now the Haynes book says there are 2 types of system ...1. has diagonal front and rear wheels working in pairs in case of system failure....2. has both fronts working together and both rears working together but as separate pairs in case of system failure.

So question now is does anyone think its the master cylinder seals that's failed or am I on the wrong track ?

Thanks in anticipation of an answer

[Van Winkle]

Bump ........any ideas anyone ?

[Keef]

Have you tried bleeding the back brakes to see what comes out?

[Van Winkle]

No Keef not yet, whats you thinking may have happened ?

[Jim Archer]

Is the handbrake adjusting up as it should?

Jim

[Van Winkle]

Yes Jim handbrake works good , holds van on steepest of hills, not sticking and only pulls up 2 clicks and wheels turn when released, im baffled

[Jim Archer]

I'd be looking at the LAV and flexi-hose, and if that's all as it should be, new mastercylinder time if it's the front/rear split version.

Jim

[Van Winkle]

Hi Jim thanks for reply and everyone else too, nothing found until today when had some time for another look at this , found some fluid leaking out of master cylinder filler cap, took top off and fluid seems to have increased and when wife was pressing pedal and then releasing it the fluid was bubbling up in the reservoir like there was air blowing up into it . But not like tiny bubbles just a big blub blub blub, weird and got me puzzled any ideas anyone ?, still no sign of leaking fluid on the brake cylinders or callipers , pipes or flexis .

[MinorMatt]

I would give the master cylinder a go

[AndyG]

Same as MinorMatt says; master cylinder packing up