Hydraulic Woes

Fred Munro munrof at sympatico.ca
Sat Nov 1 13:03:59 PDT 2008


"More than a few drops" means your servo is leaking, bleeding pressurized
fluid off the accumulator back into the reservoir. This is why the warning
indicator stays on in the morning - the accumulator has lost pressure
overnight and the light is indicating low brake boost pressure until the
pump repressurizes the system. If the servo leak gets bad enough, the pump
will not be able to maintain system pressure and the light will be on all
the time. The car is not safe to drive if the hydraulic brake boost system
pressure is low.

The light flicker on turns may be from a low level in the reservoir
activating the low fluid level sensor as the fluid climbs the reservoir side
in a turn. This will be the case if you check the level after the car has
been stopped for a while and fluid has bled back from the accumulator into
the reservoir. Check the level while the engine is running.

You can get an idea of how bad the servo leak is by stopping the engine and
watching the reservoir level. If you can see it rising, you've got a
problem. If it takes a few hours to bleed off the accumulator, I think
that's typical of these cars as they get older.

BTW, a servo for a UrS6 is around $800 - don't know about the price for your


Fred Munro
'97 S6

-----Original Message-----
From: quattro-bounces at audifans.com
[mailto:quattro-bounces at audifans.com]On Behalf Of Brian Pleet
Sent: November 1, 2008 12:48 PM
To: quattro at audifans.com
Subject: Hydraulic Woes

My wife's 90 90q20v is back on the road after a cylinder head rebuild
and timing belt change.

One last issue is the brake indicator light.

1) brake warning indicator stays on for 25-30 sec on starting, 10
secs if running engine at 2000 RPM
2) brake warning indicator lights momentarily on full L and R turn,
after pumping the brakes 10-15 times at idle, not at 2000RPM
3) whining sound when cold from 800-1200 RPM, not related to turning
the steering wheel. Loosening the pump belt helped, but its still
4) starting engine with foot on brake pedal does not change the pedal
feel and pumping after turning off the engine does not seem to
benefit from any boost
5) when the return line on the hydraulic brake servo is removed, more
than a "few drops" of fluid run out
6) brake pressure accumulator is original (unless the dealer replaced
it in the first 10 years)
7) hydraulic fluid was Pentosin, but the dealer suggested 10 years
ago that adding Lucas would stop the whining while turning
9) front brake rotors and pads were just replaced and brake fluid was
10)Hydraulic lines all show some minor seepage at joints (likely just
18 years of use) but no obvious leaks and reservoir stays full

I've just bought a new(er) accumulator and Pentosin for a flush. Are
there other parts (pump, servo, etc) I should replace at the same time?

90 90Q 20v
95.5 S6
02 TT Roadster

E-mail:bpleet at telusplanet.net
Tel:    (403) 286-0069

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