4Kq rear calipers

[paul fernandes]

Jason,
first off I want to express my thoughts and apologize on behalf of the
automotive industry and the professionalism or actually lack of it.

I have come across this incident on all my cars, actually this failure (rear
caliper seizure is normal ..if you want to call it that.)
this actually should appear on all cars after about 6-8 years cycle
time...this also depends on weather conditions as well...
obviously you being in Alaska has a big part to do with it.. Depends on
salts used..

I want to explain where I'm coming from first...I work for a very big tier 1
automotive supplier if there things that I know About cars it is components.
we are doing brake systems as well on top of (a/c systems / exhaust / brake
systems / electrical...etc...)

Now since I am an all out Audi nut I would like to explain several things
about this caliper and what I have discovered working for this joint I work
in.
NUMBER ONE REASON FOR FAILURE ON THESE CALIPERS:
there is a small seal on the shaft of the parking brake mechanism, this seal
and as anyone knows rubber seals do not last forever, wear out, crack with
time. After a certain break down period the actual task of keeping dirt and
moisture away from that shaft goes away..end result shaft corrodes
seizes...BANG not rear parking brake sometimes complete failure..

Now onto you second note:  aftermarket rebuild calipers,
I don't care what anyone says in this forum they are all crap! we have done
tone of evaluations and with close work with Volkswagen came up with is
conclusion on most (90%) of the rebuildables on the market...and this is
where I think there is a lack of responsibility from these companies.
ONE of the most common mistakes done by rebuilding is just that...rebuild..
you see after some parts are worn out or even corroded they must be machined
in some case we noted even sand blasted??????
to gain back some sort of surface.
This results in minimizing of a certain contact area need to assure leak
proof-ness.
-top no nos in rebuild calipers as targeted by VW/Audi
1) low quality of piston seal
2) lack of corrosion resistance in outside body as well as some caliper
components (mostly painted)
3) re-bored parking brake rod cylinder (too loose)
4) weak or substandard slide boots covers (rubber things that cover piston
slide rods)
5) incorrect or no use of seal in parking brake rod...used instead a copper
sleeve..
6) piston to piston housing tolerances as high a 05. mm gap nominal (OEM
0.05)
7) wrong strength class fasteners 8.8  ....should be 10.9
8) use of sub standard o-ring on piston push rod.
***)There were more points but I am not at work ..and don't remember them
all...anyway

Now take a look at that #8 I left it for last just to explain this one
because this is where I think
yours may have failed.
On the rear caliper there is a mechanical piston which is connect to the
parking brake lever...
sort of like a engine piston rod sort of.
Any way this rod is underneath that spring you see when you remove your
piston from the housing.
The spring is kept in place by a cup or cover which in turn is secured by a
c-clip.
once this is removed (VERY CAREFULLY) you will see it...
now because these piston is linked from the back (parking brake lever)  to
the front to actuate the piston
there is a theoretical air gap which would leak all fluid out..this are
right between the rod is seal with a very small
o-ring....this o-ring sometimes is neglected or not even touched upon
rebuilding..even though for example
it might have been scratched and then making it almost useless...

This is pretty much the short version of this story..sorry everyone..
If you need more details contact me off-line and I can send some pictures of
these things taken apart
for reference.

fianl conclusion check that rebuild part recarefully and ask what was
rebuilt when
you by one...good luck...

Paul F.
(Luxembourg)
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----- Original Message -----
From: "Jason Gray" <jason510 at att.net>
To: <quattro at audifans.com>
Sent: Saturday, January 25, 2003 10:01 AM
Subject: 4Kq rear calipers


This is a multi-part message in MIME format.
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[ Picked text/plain from multipart/alternative ]
When I got my '87 4Kq a couple of years ago, the parking brakes on the rear
calipers were  siezed and non-functional.  I replaced both rear calipers
with "Cardone" brand remanufactured girling calipers ordered from parts
america.com and the rear brakes (and parking brakes) subsequently worked
fine.

Now, 2 years later, one of the "rebuilt" calipers is giving me trouble. The
faulty caliper is leaking brake fluid out the back of the caliper casting,
through the parking brake mechanism. The first time it did this was a very
cold nite (0°F), not sure if the cold had anything to do with the failure? I
first noticed that the brake pedal was too soft, dash waring lite came on
and also that there was a puddle of brake fluid on the ground below the
faulty rear caliper. I could see the brake fluid leaking out the caliper
casting through the shaft of the parking brake mechanism actuating arm. I
dont think that the fluid is supposed to be present in the parking
mechanism?  I removed the caliper and removed the cylinder from the bore but
didnt notice the source of the leak into the parking mechanism.  I cleaned
the cylinder and bore and re-assembled and it did not seem to be dripping
fluid as before. I bled the brakes and was able to drive for couple of weeks
without problem (firm pedal, strong brakes) but then I noticed that the
level of the resevior was going down, apparenly slowly leaking through the
same caliper. Then, lastnite the same caliper suffered another catostrophic
leak and dripped all the fluid from the circiut.

Is this a "normal" failure mode for the 4Kq rear calipers? After removing
the piston, it was not apparent to me how to further dissasemble the caliper
&  parking brake mechanism, bently is no help. Can anything be done to fix
this leak? Since it is not leaking out past the cylinder, it seems that the
fault is part of the parking mechanism, any parts/seals that I can replace
to fix?

THanks-
Jason Gray
Anchorage, Alaska
'87 4Kq
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