[s-cars] Ongoing Hydraulic system issues (LONG)

[Andrew Beckert]

Open letter from my mechanic concerning the ongoing saga of my car.  Any input is greatly appreciated.  His letter is below and I would be happy to answer any additional questions.

thanks, 

Andrew Beckert
1995 Audi S6

Hi ,
 I need help.  Here is the story.  It all started with a brake pressure
accumulator.  After replaceing the brake pressure accumulator, the customer
complained that the car twice at start up had a stiff brake pedal and no
power assist.  Sounds like possible air in the pump.  Car came in but the
problem had gone away.  All looked ok.  Fluid level was correct no noise.  
Customer took the vehicle and said they would monitor the problem and report
back.  Brake pedal problem never reoccured but steering problems continued.
The car returned for more checks.  The steering was hard in one direction
and easy in the other.  Sometimes if you started to turn to the right sitting
still the wheel would turn on its own all the way to lock.  Sounds like a
spool valve problem in the rack.  Replaced the rack.  Car now did not turn
on its own and steering felt ok.  Returned the car to the customer.
Customer said the car was better but twice (once while turning into a
parking place) the assist went away.  He returned the car for more tests.  I
found the rack was leaking from a brass plug in the spool and when the car
was hot the assist changed with engine speed. Sometimes it felt like no
assist at all.  Rev the motor and assist might return.  I replaced the
leaking rack and rechecked.  The new rack did not leak but assist was not
correct.  I bypassed the servotronic relay to make sure it was not a problem
in that system.  No change.  Assist changes with engine speed.  Must be a
pump.  Replaced the pump.  Prime the pump on the bench to try to eleminate a
bubble traped in the pump.  No change.  Talk to audi and zf for support.
They both say you must have a bad pump.  Replaced the pump again.  No change. 
Maybe I have a restriction in the pressure hose or return hose.  Swap the
pressure hose with another known good and run a seperate return hose.  No
change.  It all started with the accumulator even though they are seperate
sections of the pump and I didn't think there could be a connection I
replaced the accumulator again.  No change.  I then thought maybe zf has a
batch of seals that are the wrong size or something.  Purchased a reman rack
from Audi.  No change.  (Audi rack is probably a ZF reman but needed to try
something different.)  The fluid is chf 11s and last time i used genuine
g002000.  I am going to mark the balancer today to check for slipping but
dont expect to see any.  No noise like a slipping balancer.  Does anyone
have a suggestion?  I sure would like to here from you .

I also noticed that when the tie rods were off and I rotated the wheels back
and forth, the right wheel felt rough.  I replaced both upper strut bearings.  
No change.

thank you