A4 quattro brake problem..

[Kneale Brownson]

--
There's a considerable difference between your pushing on the piston with
some water pump pliers and the brake pad vibrating the piston back into
place as it bounces off the rotor.  If the brake fluid is what was
installed in the factory four to five years ago, it well could have picked
up enough moisture from condensation to cause corrosion in the cylinder and
on the piston.


At 02:45 PM 01/16/2002 -0500, Kris Hansen wrote:

>CAr is a '98. I doubt that the caliper is the problem, considering how
>easily the piston retracted with the bleeder open slightly (I just use a
>large pair of slip joint pliers) MC only has 2 lines out of it, I assume
>front and rear? The ABS unit splits the lines side to side after the MC. The
>only brake with this problem is the driver's front. A European car
>specialist friend of mine seems to think it may be a bad hose. He said that
>he has not seen an ABS pump unit cause this type of problem (or any problem
>apparently) Do you suppose that the hose could have a blockage? Bear in
>mind, that the caliper will eventually relinquish it's grip if left to sit
>for a minute or two (when cold anyway).
>
>Thanks!!
>
>Kris
>
>-----Original Message-----
>Kneale Brownson wrote...
>--
>How old is this car?  Has the brake fluid been flushed out?  My bet would
>be if you disassembled the caliper you'd find some corrosion in the
>cylinder or on the piston that occasionally doesn't let the brake pad push
>the piston back in enough to release totally from the rotor.  My first
>guess would be the master cylinder, but if it released on rough braking,
>that makes me suspect the corrosion.
>
>
>At 08:04 AM 01/16/2002 -0500, Kris Hansen wrote:
>
> >Good morning all,
> >
> >I have a problem with the driver's front brake, the caliper doesn't seem to
> >want to let go of the rotor. I took the caliper off, cleaned the guide
>pins,
> >retracted the piston (which didn't take any unusual force with the bleeder
> >cracked slightly) put it all back together again, and it still sticks. Has
> >anyone had an ABS pump unit go bad, where it wouldn't back flow fluid? My
> >initial thought was caliper, but I am now thinking because of the relative
> >ease with which the piston pushed in that the actual caliper is not the
> >problem. The pedal feels fine, though on the second push, it is firmer than
> >on the first. The only thing I did not do was crack the bleeder with the
> >caliper stuck, to see if it would release (and spew fluid out, I guess
> >indicating a blockage upstream?). This is scheduled for this evening.
> >
> >An interesting note, on the drive home, before I noticed that the brake was
> >sticking, the car pulled heavily under braking. I gave it some very hard
> >stops, and it stopped pulling. Any help will be greatly appreciated!!
>
>
>_________________________________________________________
>Do You Yahoo!?
>Get your free @yahoo.com address at http://mail.yahoo.com
--