[s-cars] More on Front Brake calipers not releasing

[Scott Justusson]

Gents
A couple more comments, then I go back to lurk mode.  WRT Fluid, IME ATE
superblue eats seals.  I use either the factory Pentosin I buy by the
gallon, or if a track car, I use the valvoline synthetic available at
your local autoparts store.  I'm a believer that if brake fluid boils at
500 (V-S) vs 550 (ATE), you already have a heat problem that needs
addressing.  IME Ducting air to brakes helps that more than a 'better'
fluid. BTDT

WRT identifying the problem itself, this sounds to be a MC with
obstructed passages.  The easy test is to get the lockup in the fronts,
and crack the MC line to the front brakes.  That positively will
eliminate the caliper pistons, but IME, doesn't necessarily eliminate
the hose deterioration.  After chasing that myself on a car, thinking
the test did eliminate the hoses, it didn't = long day.

Pressure Bleeders:  IME with the Audi ABS solenoids, it's really tough
to properly bleed the brakes without a pressure bleeder.  I bought the
Snap-on one over 15 years ago, and it's due for it's second rebuild
soon.  I won't say you 'can't' bleed brakes using the "up/down" method,
I just haven't for years.

Make sure you flush the reservoir with clean brake fluid and compressed
air if replacing the MC.  A new MC can clog pretty quickly with the same
gunk that killed the old one.

IME2, I have saved quite a few master cylinders by removing them and
bench cleaning them with brake fluid and compressed air.

HTH

Scott J





-----Original Message-----
From: Peter Schulz [mailto:pcschulz at comcast.net] 
Sent: Wednesday, April 22, 2009 8:06 AM
To: Scott Justusson
Cc: s-car-list at audifans.com
Subject: Re: [s-cars] Front Brake calipers not releasing.....Master
Cylinder?

Scott:

What do you recommend for brake fluid in lieu of the Super Blue?


-Peter

At 07:35 AM 4/22/2009 -0500, you wrote:


>Both masters use discs and antireversion dampening in the fluid return
>circuit.  These are very small passages that serve to slow down and
>dampen fluid return into the master cylinder.  IME, they can get
clogged
>easily, especially with old fluid, or running ATE Superblue Fluid.
IME,
>most Master problems on S cars are caused by this symptom.  That said,
I
>have also seen bad brake line internals cause the exact same problem
>too, as Scott N notes this am.

-Peter Schulz
Chelmsford Ma, USA
http://www.naaclub.org/

1995.5 S6 Avant Emerald/Ecru
1995.5 S6 Avant Silver/Platinum
1991 90 20v Q Red
1991 CQ silver  (eS2 recipient)