Rear brake caliper disassembly; 4000Q or 80-90Q

[Louis A. Mulieri]

Hi Greg,
	Here's my experience with rear calipers on my 88 5KCSTQ that were
sticking the e-brake on. I first tried to free up the actuating lever/rod
by prying it out 1/4" to clean up the rust with fine emery and new
lube. When I pushed the rod back in I found it no longer controlled the
piston motion. Another lister wrote that I had dislodged the medicine
capsule like steel rod that connects the shaft to the piston. So I removed
caliper and like you was stumped at getting out the central threaded rod
out of the cylinder after removing the snap ring. It is just held in with
a piston-like enlargement at it's bottom. It wouldn't simply slide out
only because it was gummed up. After 2 hours of fiddling I did use the
2-screwdriver method of levering up on the threaded rod. Got a few nicks
in the threads which I carefully filed completely smooth so the
auto-adjust nut would not catch on it.
	Below is a description I sent to another lister who needed to know
what is inside the e-brake section of the caliper.
========================================================

Here is what is inside my caliper. The E-Brake shaft extends inward to end
about 10 mm beyond the center line of the caliper piston. This shaft has a
circular depression drilled near its inside end. The depression is drilled
perpendicular to the length of the shaft but it is drilled about 5 mm
outside the centerline of the shaft. Visualize it to be sort of like a
woodruff key slot near the end of a shaft but with the shaft matal milled
away on one side of the slot to create a step in the side of the shaft. If
you hold the shaft horizontal with the opened side of the slot pointing
upward you can put the tip of a small phillips screwdriver on the
remaining side of the slot acting as a step. With the screwdriver held
vertical rotating the shaft about its long axis will angle the step upward
lifting the screwdriver a small amount. This is the Instead of a slot in
the side of the e-brake shaft there is a circular, cone shaped depression
creating a step. This step supports a mating steel rod with rounded ends
about 20 mm long and 5 mm diameter (looks like a drug capsule). One end of
the rod sits in the offcenter depression of the e-brake shaft and the
other end mates into a similar depression at the center of the auto-adjust
spindle that screws into the inside end of the caliper piston. Thus,
rotating the e-brake shaft lifts the rod pushing the piston outward as
though hydraulic pressure had been applied. When I finally got my caliper
open I found the rod had not fallen out of its step seat but rather, the
trouble was that the the auto-adjust spindle was pulled out of contact
with the "medicine capsule". Rotating the E-brake shaft did push the
capsule in but it was not in contact with the caliper piston. The reason
was that when I screwed the piston inward to make room for the new pads
and rotor that I had installed I did not push inward firmly on the piston
as the Bently describes.  So here is what to try. With pads and rotor off,
rotate the piston CCW while pushing it firmly inward. If the brake cable
is not binding the e-brake lever you will see the lever move toward full
off postion. Stop rotating the piston when the lever has reached its
full-off stop. You should be fixed now.

 > --__--__--
>
> Message: 5
> From: "Greg Galinsky" <nokian at aaahawk.com>
> To: <quattro at audifans.com>
> Subject: Rear brake caliper disassembly; 4000Q or 80-90Q
> Date: Fri, 8 Nov 2002 22:03:29 -0600
>
> This is a multi-part message in MIME format.
> --
> [ Picked text/plain from multipart/alternative ]
> Just got done looking in the archives to no avail.  Looking for in depth de=
> tails on the disassembly of the parking brake internal parts.  Have the int=
> ernal snap ring off and nothing happens. What am I missing?
> TIA
> Greg Galinsky
> 1990 80Q
> --
>
>
>