5000s brake woes

[Alexander van Gerbig <avangerb@zoo.uvm.edu>]

My sister owns an '86 5000s Automatic.  The car has a funny problem that
I have never heard of before.  She was driving down the highway and
hadn't touched brake pedal for quite sometime, when she did go for the
brakes the pedal was rock solid giving only about an inch of travel then
going hard.  After noticing this she released the pedal and began to
notice that the car began to slow on it's own.  The car's brakes were
grabbing more and more by the second.  She accelerated and the car still
became slower.  The steering wheel began to shake, so she pulled off to
the side of the road.  Slowly but surely the brakes let up and she was
on her way, although it took some time.  This brake seizing had occurred
before in stop and go traffic.  After a couple minutes of driving or
waiting will fix the problem.  Any ideas guys?  Maybe the accumulator?
Brake fluid is still amber, not dark.  Has new bleeder nipples in the
rears, new flex hoses all around, and new rotors+pads in the front.

Thank you,
Alexander van Gerbig '88 80
The Audi 80 Pages
http://surf.to/the80pages.com

Family Audis
------------
'86 5000s
'88 80
'91 200q20v Avant
'91 90q20v
'92 100s
'96 100csq
'98 A4q1.8t