[s-cars] Rear brake caliper sticking

[Tom Green]

Rich,
I would suspect the caliper carriers rather than the caliper pistons  
themselves.
Inspect the pads for uneven wear and you will probably find one worn  
out because
the carrier pins are not letting the caliper center on the disc  
causing it to drag all the
time, so the brake probably heats up without a couple of hard stops.
If they really heat up, you may benefit from new  or rebuilt  
calipers, but I suspect you
can correct this problem by cleaning and lubricating the carrier  
pins.   Bleed the brakes
to flush out the old fluid if you haven't in a year (or two).
I share your concern about caliper rebuilders, but I don't have any  
advice on who the
good ones are.  There is some DIY stuff in the knowledge base for 20v  
and 200 20v
and Audiworld if you are into projects.  Allows you to paint the  
calipers and carriers
while you have them apart.

Tom


> Richard complains:
>   I'm having trouble with one of the rear brake calipers sticking, it
> works fine when cold, after a couple of hard stops it doesn't  
> release all the
> way.  Once it cools down completely it's OK again.  It's already been
> replaced once a couple of years ago with a rebuild.  I lubricate  
> the hand brake
> cam regularly, in fact it was lubed just a couple of months ago  
> when new
> hand brake cables were installed.  So my suspicion is that it's the  
> piston
> sticking.
>
> I guess it's time to put in another rebuilt caliper, anyone have a
> source for high quality rebuilds?  My feeling is most places just  
> clean up
> calipers and pop in a new piston seal, without rehoning the  
> cylinders, measuring
> for tolerances, etc.   I don't want to keep doing this over and  
> over...
> Or bite the bullet and put in a new one?
>
> -- Rich A.
>    '92 & '93 S4