dead clutch

[Joel Skousen <jskousen@enol.com>]

I believe the top seal in your clutch master cylinder piston is
binding.  This is a typical audi MC problem.  The seal on top is made a
little too tight to begin with--it isn't as flexible as the bottom seal,
and the sealing lips don't flare out as much.  All of this makes it easy
to bind at the least provocation.  In the presence of old break fluid
(that has taken on some moisture) the seal tends to gumm up and bind on
the sides of the cylinder--hence it won't come all the way back up. 
Sometimes you can get it to work again by "flipping" the pedal--pushing
down part way with the edge of your foot and letting the peddle slip off
the side of you foot and it spring back rapidly--that has allowed mine
to come back to life temporarily in order to get me home.  The only
final  solutions is a rebuild kit.  The new seals in the kit I recently
got are not as large as the old ones, so there is more clearance to move
freely.  They should not have the same binding problem in the future. 
	Note, if you choose to rebuild a master cylinder, make yourself a an
INSERTION SLEEVE out of type M  3/4 copper pipe (about one inch long). 
You have to insert this in the top, open end of the master cylinder in
order to get the new piston and seals past the circlip retention
flange.  If you don't use an insertion sleeve, the seals (which point
downward) will catch on this flange lip and be sheared off or damaged as
you press the new piston in.  The sleeve effectively removes the flange
by filling this larger bore area at the top with metal (the sleeve). 
Now, as you insert the new piston w/seals, it will slip in fairly
easily.  Failure to use an insertion sleeve is the main reason most
rebuilds of master cylinders by back yard mechs don't turn out very
well. 

 One final note on the sleeve construction.  You have to cut about an
1/8" slot out of the sleeve, lengthwise, with a hack saw in order for it
to compress down to fit into the upper opening of the master cylinder
case.  If you are using type "L" copper (thinner) you may even have to
slice more out so that the inside diameter of the sleeve exactly matches
the inside diameter of the cylinder bore. Matching the inside bore
diameters is the key.  Do whatever cutting you need to till the sleeve,
when compressed down, matches ID to ID.  I did this by cutting and
filing a little bigger slot and then putting a couple of wraps of scotch
tape around the outside of the sleeve so it would fill in the gap and
press into the upper part of the MC snuggly. Type M copper is thicker
and more closely matches the thickness you need to achieve.  This may
seem like a lot of trouble, but once you have made one of these sleeves,
fixing a MC is an easy task whenever you have to do it--and it only
costs you about $30 plus your labor to pull the MC and reinstall. 
HTH  JOEL