[s-cars] brake failure

Peter Golledge petergolledge at gmail.com
Tue Sep 22 21:02:07 PDT 2009

Having been through some S6 brake/steering nightmares recently myself... I
would suggest:

1.  The fluid coming out of the top of the reservoir is most likely the
infamous "pentosin fountain" most likely leaking "caps" on the pump sucking
in air and frothing the heck out of the fluid.  You can remove the caps and
replace the O-rings without a complete rebuild.  You will need the help of
place dealing in metric seals to get the metric O-rings.

2.  Flush ALL of the hydraulic fluid especially the reservoir, lots of gunk
accumulates in the there and can clog the screens on the banjos.  While
troubleshooting I use Shell Tellus 32 Plus, once I've got stuff working I
drain this and put in the "Green Gold".  As part of the flush check the
screens on the banjo bolts.

3.  Flush the Brake fluid side of things, I figure this would already have
been done with a MC replacement.  The Scott J suggested NOT using ATE
Superblue as it doesn't play nice with the 95.5 system I have.  Alternative
suggested was Valvoline Synth Dot 4.

I've replaced everything _other_ than the servo (Bomb, Both HP hoses, rack,
pump and MC) as I've gone through both braking issues and a rack replacement
gone bad. :-)  

-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] On Behalf Of james McCarthy
Sent: Tuesday, September 22, 2009 8:49 PM
To: s-car-list at audifans.com
Subject: [s-cars] brake failure

Here's the story.
Brakes have been running fine - thought have suspected the servo might be
starting to go.  
Drive to work no problem.  Come out to drive home - no brakes - rock hard
pedal.  Open hood and the p reservoir is is all wet on top - best I can
figure it looks like the fluid was forced out of the cap.  After 10 minutes
of idling the brakes sort of came back - a bit firm but working.  So I
limped home (3 miles) and immediately after stopping pedal was rock hard and
now wouldn't come back - thought no further fluid loss.  So thought it was
the servo - and replaced it... now the fun begins.
First - pedal is still rock hard - though is compressible - but with
Second - when first assembled the wheels were all locked - like the brakes
were activated.  Separating the servo and MC released the wheels
So questions:
1) MC failure?  seems unlikely to have caused my initial symptoms. Also when
assembling the MC and servo - should it just slide together or is there a
little "pressure" as they engage - compressing the MC piston... I had this.
2) Bomb?  it's less than two years old but possible I suppose... still
doesn't explain the problem with the locked wheels after swapping the servo.

Any wisdom would be appreciated.

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