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frozen rear calipers on 200q

>F6rgen_Karlsson?= <jurg@2.sbbs.se>
>Subject: Rebuilding frosen rear calipers on a 200 quattro in Sweden,
please help.
>Is this anything I successfully can repair myself?
>I have heard on the list that some of the rebuild kits are defective.
>I have tried buying parts in the US using Swedish part# and I have never
>succeeded for example the brake bomb was a totally different part. The last
>time I tried to buy the rear callipers, there were no such part. These
>numbers are most definitely valid in Sweden.
>Funny prices:
>It now seems like we have a major revision of prices here in Sweden, this
>haven't hit the rear callipers yet, they are three times the price of the
>bomb. The bomb was 900$ before. The callipers are 700$ now!
>Is a 5000cs called a 5000tq on the list. (In Sweden Audis have always been
>called 80,90,100 and 200.)
>Jörgen Karlsson


Things to watch for: Some rear calipers are 34mm diameter pistons, some are
36mm (or maybe it is 36 and 38) - but there are TWO different sizes.
Measure your caliper pistons to get the right parts.

The calipers may not be frozen at all - it is possible that the
proportioning valve inboard of the left rear wheel is stuck. Try bleeding
the brakes; if nothing comes out of the rear calipers, it is the
proportioning valve, not the calipers that is your problem. I will say if
the valve has been stuck a long time, the calipers will need to be rebuilt
anyway from non-use. The proportioning valve has a big spring which
connects to a lever, and the lever presses on two valves - if the valves
are stuck, the assembly must be replaced - junkyard part, don't even think
about buying new! Check the replacement part to be sure it isn't stuck, too.

The calipers can be rebuilt, but they are complicated. There's a diagram
with the rebuild kit - you'll need some inside snap-ring pliers, probably a
bench vise, lots of parts cleaning fluid (mineral spirits), and some time.
There are all kinds of little passages in the caliper which can trap dirt,
and you'll be astonished at the garbage that comes out when you clean it!

Another trouble spot is the parking brake pivots - these are usually stuck,
but lots of WD-40 or other penetrating oil will help. You can pull these
pivots out of the caliper a short distance (don't take them all the way out
- it will be difficult to get them back in) and sand off the rust and crud
on the shaft. Lubricate and reinstall.

If the rear brakes have not been working (for whatever reason), the rear
discs may also be rusted - check them.

Finally, make sure the guide pins move easily, and you are supposed to use
new bolts upon re-assembly, but carefully inspecting and cleaning the old
bolts plus some lock-tite seems to work fine (nomex on).

The biggest problem is that this always turns into a BIG job - all kinds of
things are stuck, rusted, corroded, worn out, etc., but when you are done,
you'll be amazed at how good the brakes are!

Incidentally, a 5000cs is a 100, and a 5000TQ is a 200 (more or less). 200
series cars are turbo, and 100 series are not - note that turbo is not
always quattro, and I have heard of a few quattros that were not turbo. In
the US, most "plain" 5000s are 2 wheel drive, non turbo, and most quattros
are turbo: 5000TQ. Finally, the 100s use the smaller rear brake calipers
and the 200s (and 100 avants) use the bigger ones, but after (I think)
1988, they all use the bigger ones. Biggest problem is to get the exact
parts - the serial number may help, but not always!

Best Regards,

Mike Arman