Audi Rear Caliper (1989)

[james accordino]

--- Paul Heneghan <paul at heneghan.co.uk> wrote:
> Hello James and other parking brake mech experts.
> 
> I found your learned articles on rear caliper
> dismantling in the archives.
> I have reached the stage where I have removed the
> circlip at the base of the
> cylinder.  Now I need to extract the stud.  Any
> ideas?  I tried putting the
> piston back on and levered the piston upwards.  Al
> that happened was the
> outer shell of the piston came away from the inner
> bits.

I am going from memory.  Unfortunately I didn't take
any pictures or make any notes.  I only disassembled
the inside of the piston once, when it looked gooped
up.  I found the best way for me to get the stud out
was to rotate the brake lever as far as possible.  If
you remove the stop screw (10mm socket) you can rotate
it alittle farther than normal and this will help push
the piston stud out alittle bit more.  Then I screwed
the piston part way on the stud.  Remove the o-ring
and boot from the piston.  Then I pounded the caliper
on a soft (relative) object like a block of hardwood
or something that won't damage the cast iron.  If you
pound the caliper down so that it hits on the ears and
the piston face is down its' own weight will act like
a slide hammer.  IOW the piston will want to continue
down and pull the stud with it.  Most come out in 1-5
pounds, but one took at least 20-30.  Your pounding
may vary.  The deal seems to be that the o-ring around
the base of the stud gets stuck from being hard or
sludge and just won't retract, keeping the parking
brake on.  BTW, were your piston or walls pitted?  I
haven't found one yet that was bad, except the one I
cut in half that sat under mud/water for at least a
year.  All the crud and surface rust is in that part
below and behind the piston.  I wish I could remember
the EXACT details of the assembly under there.  The
"pill"  is the primary action part as it transfers
rotary motion of the parking brake lever to the linear
motion of the piston stud.  Under or around the piston
stud are an o-ring, a small cup-like piece that seemed
to be made of stainless? steel, and a wave type
spring.  I believe these are the components, but since
I don't actually have those pieces to look at, I
cannot absolutely verify that.  Anyway, I will
continue to try to be as little help as possible.

Good luck
Jim Accordino