Help Urgently Needed - Brake Master Cylinder

[93URS4Avant]

Peeps,

In desperate need -

Background:
Driving URS4 on Monday - steam eminating from engine bay as I was driving - pulled over and looked under bonnet with engine running to see fluid dripping from bottom of master brake cylinder all over the hot DP and steering gear resulting in the steam/ vapour which was the brake/ABS fluid hitting the hot surface.
AA arrived - scratched head and agreed MBC was defective and towed me to local mechanic who has replaced MBC and brakes seem to be fine. Where we hit a snag is that the ABS system which seems to somehow share the MBC with the braking system seems to be consuming the fluid which is causing a great concern - now this isnt a 100% accurate description of the behaviour and the ins and outs and this is where I need help.

I am in the process of installing the Audi mechanical workshop software giving me the images of my vehicle so that I can return to the garage in the morning in the hope that he can see what the parts actually look like and try and understand how these components interract, and therefore identify the possible root cause of this behaviour. Can anyone shed light on this subject - is anyone out there able to participate on a call in the morning to discuss how the system works? I have a conference facility which could support multiple users, alternately if anyone is feeling brave and PM me your number and this chap and I can call you directly to discuss.....
I woldnt make such a fuss but I am supposed to be driving to Gatwick on Saturday for two weeks sun and fun with family in Florida and I really need to help these mechanics to help me so any assistance would be hugely appreciated.

Cheers chaps.

[93URS4Avant]

Guess thats a no then!!!

[Al Wyn]

Damian have you tried pming K17ERG he is always has lots of spares hth

[93URS4Avant]

Have just returned from garage - having replaced MBC, they are now looking at the Brake Servo. The trouble is - that between Nationwide Accident Centre, Audi in Poole, TPS in Poole, GSF and Euro in Poole - no one understands how the brake/ABS system should or does work, and therefore dont really know how to fix it - the issue is that with the new MBC on - there is still a small amount of fluuid leaking from what seems to be the join between the MBC and Brake Servo (which shall be known as BS for the duration of the thread LOL) the current challenge is to understand whether the BS should be sucking in the oil - effectively does it work on a vacuum or should it be blowing - doesnt know. I am at technical with cars as a chocolate fireguard so this is just not my arena. My hat off to the guys at Nationwide - they are doing everything they can - but ther is a knowledge gap here which we are suffering to bridge.
Oddly enough I was thinking the same as you and will ping K17ERG - TOM23's URS? just died AFAIK so could be a potential source - dont suppose anyone has a URS4 brake servo kicking about???

[Error404]

Servo brake assist and brakes themselves are on separate circuits.
Servo is the same circuit as PAS. so if your fluid leak is brake fluid, its likely it has nothing to do with the servo. Vice versa is the fluid leak is PAS fluid.

If its the same type of set-up as the B3 / B4 hydraulic system, the Servo brake assist is via the PAS pump. the PAS pump has two separate vanes and circuits, one for brake assist, one for the PAS itself.

[Error404]

if you have fluid leaking from between the BMC and Servo, likely to be PAS fluid, as the pushrod seal in the servo may have gone.


what do you mean that the ABS is "consuming" fluid?

[93URS4Avant]

OK - a little more colour - the PAS fluid is leaking from the unit - as soon as the car is started the car drains of PAS fluid within 40 seconds indicating that the vacuum in the servo is not being maintained and that the PAS fluid is being brought passed the seals.

[S2central.net]

'vacuum in the servo' - not a UrS4 surely... the servo is hydraulic - same as S2/RS2.