Fw: [s-cars] Rear brake caliper sticking

[motogo1]

In addition to Peter's info, I had saved the following. I took a couple of
these apart and the shaft of the e-brake was rusted. Cleaned it up and a new
seal for the shaft solved the problems. Can be a PITA, but it can be done.

Gary Martin
94 UrS4
91 200 TQA

It is always important to frequently re-bleed/change the brake fluid to
keep internal cylinder and piston from corroding, but the ebrake chamber
is isolated from the rest of the piston by a seal and contains no brake
fluid.  Corrosion at the ebrake shaft and dried up grease in the chamber
are the usual culprits for the ebrake lever not returning.  Here's my
recent write up on repairing the ebrake system in the caliper:

(Referring to previous post about not finding an appropriate circlip
pliers)...  I had the same issue finding a circlip pliers that was long
and skinny enough to remove the circlip holding the piston in the bottom
of the caliper body.  I bought a cheap pair of needle nose pliers with
long and skinny ends and simply filed the ends round to fit the circlip
holes (got a pair that had a spring and about 4" long ends). That
circlip holds a sort of cage that holds a spring under pressure. In the
center of this is the threaded rod that the piston rides on. There is
not a lot of room, but enough to get the skinny pliers in.  Be very
careful since when the circlip is released the spring will shoot the
spring holding cage (spring keeper) and itself into orbit.  The second
one I did I put the caliper in a vice to steady it and held a small 2x2
piece of wood on the top of the spring keeper as the circlip was removed
- much less fun, but safer.  Once the spring, spring keeper and threaded
rod attached to the lower plate are removed, you can get at the inside
of this chamber.  Inside this chamber you see the e brake shaft and a
small jelly bean shaped thing (piece of metal rod rounded of at each
end) that is held between an indent in the e brake shaft and an indent
in the threaded rod shaft.
  At this point you can take out the e brake shaft and clean it up with
some sand paper, coarse to fine grain (the corroded shaft is the reason
the e brake lever does not return).  Also clean up the old grease and
re-grease the cavity with high temp. lithium grease (or marine grease -
may improve the rust corrosion issues with the shaft). The seal where
the e brake shaft goes into the caliper is a simple oil seal.  I got
mine at a bearing supply company.  I found a TCM oil seal part #
16x24x7TC (16mm {shaft opening }X 24mm {outside diameter) X 7mm
{thick}).  Refit the jelly bean and the brake lever shaft and threaded
rod w/ bottom plate.  Now comes the fun - the spring and spring keeper
must be compressed in order for the circlip to seat.  I used an
appropriate socket on the spring keeper that covered the keeper, and
allowed the threaded rod to pass through.  Then took a large C clamp and
clamped the socket down to compress the spring so the circlip could
fasten.  It takes a little trial and error and you have to center the
spring keeper a bit (first thing under the circlip before the threaded
rod plate).  Sounds worse than it is.  Once it is together there now
enough spring tension to reset the e brake lever even before the outside
spring clip is attached. They have been working like brand new calipers
for over 6 weeks - no lock up of the ebrake cable and plenty of holding
power.

Good Luck,

----- Original Message ----- 
From: "Peter Schulz" <pcschulz at comcast.net>
To: <konecc at snet.net>; "S-Car-List" <s-car-list at audifans.com>
Sent: Wednesday, December 14, 2005 10:14 AM
Subject: Re: [s-cars] Rear brake caliper sticking


> Rich:
>
> Based on my experience, the root cause is the ebrake mechanism on the
caliper.
> You indicated that you lubricated the cam, but do you in fact have full
and
> complete travel? - remove the spring external to the cam and check.
>
> On a new caliper or correctly rebuilt one, the spring under the caliper
> piston provides enough pressure to move the ebrake cam back and forth
> without the additional spring external to the caliper.
>
> -Peter
>
> http://www.20v.org/brakere.htm
>
>
>
>
>
>
>
>
> At 09:15 AM 12/14/2005, Rich Assarabowski wrote:
> >   I'm having trouble with one of the rear brake calipers sticking, it
> >works fine when cold, after a couple of hard stops it doesn't release all
the
> >way.  Once it cools down completely it's OK again.  It's already been
> >replaced once a couple of years ago with a rebuild.  I lubricate the hand
> >brake
> >cam regularly, in fact it was lubed just a couple of months ago when new
> >hand brake cables were installed.  So my suspicion is that it's the
piston
> >sticking.
> >
> >I guess it's time to put in another rebuilt caliper, anyone have a
> >source for high quality rebuilds?  My feeling is most places just clean
up
> >calipers and pop in a new piston seal, without rehoning the cylinders,
> >measuring
> >for tolerances, etc.   I don't want to keep doing this over and over...
> >Or bite the bullet and put in a new one?
> >
> >-- Rich A.
> >    '92 & '93 S4
> >
> >
> >
> >_______________________________________________
> >S-CAR-List mailing list
> >S-CAR-List at audifans.com
> >http://www.audifans.com/mailman/listinfo/s-car-list
>
> 1991 200 20v Q Avant Titan Grey
> 1991 200 20v Q Avant Indigo Mica
> 1991 90 20v Q Red
> 1990 CQ silver (awaiting S2 engine transplant)
>
> 1990 CQ red ( to part or not)
> Chelmsford Ma, USA
>
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