[s-cars] occasional brake light on start and sometimesdifficult steering - hydraul flushing?

Thu Jun 25 20:45:31 PDT 2009

Chris, I don't know if you follow Mance's antics on QW, but I'm running Mobil1 synthetic ATF in the hydraulic system right now along w/ pentosin.

Wylie Bean
TheRingmeister at triad.rr.com
90 cq
91 90q20v
92 UrS4
08 Q7 3.6
Sent on the Sprint® Now Network from my BlackBerry®

-----Original Message-----
From: chris chambers <fastscirocco_2000 at yahoo.com>

Date: Thu, 25 Jun 2009 20:32:26 
To: Fred Munro<munrof at sympatico.ca>; Jared Robinson<chapel976 at gmail.com>; <s-car-list at audifans.com>
Subject: Re: [s-cars] occasional brake light on start and sometimes
	difficult steering - hydraul flushing?

Gentz,

is there a hydraulic fluid that can be used in place of pentosin's liquid gold for flushing the system?
Obviously after flushing fresh Pentosin would used.

Chris

----- Original Message ----
> From: Fred Munro <munrof at sympatico.ca>
> To: Jared Robinson <chapel976 at gmail.com>; s-car-list at audifans.com
> Sent: Thursday, June 25, 2009 9:44:24 PM
> Subject: Re: [s-cars] occasional brake light on start and sometimes difficult steering
> 
> Jared;
> 
> The hydraulic pump has two circuits; a high volume low pressure circuit for
> the power steering and a low volume high pressure circuit for the brake
> assist. Both circuits are fed from the common fluid reservoir. 
> 
> In the power steering circuit the pump pressurizes the fluid and sends it to
> the steering rack. Fluid from the rack goes through an oil cooler (a
> U-shaped black steel tube mounted at the bottom of the AC condenser) and
> back to the reservoir.
> 
> In the brake boost circuit the pump pressurizes the fluid and sends it to
> the brake boost servo and to the accumulator. The accumulator stores
> pressurized fluid so you will have brake assist if the engine stops while
> the car is in motion. Normally the pump pressurizes the accumulator until it
> is charged and then fluid is bypassed to the reservoir. When you apply the
> brakes, pressurized fluid flows into the servo to give brake assist and then
> flows back into the reservoir. When the engine is stopped, the system should
> hold pressure in the accumulator.
> 
> With age, the brake servo can leak by and/or the accumulator bypass valve
> can leak by. This drains fluid from the accumulator back to the reservoir.
> If enough fluid drains back, the pressure falls below the low pressure alarm
> point and the "brake" light comes on to warn of low brake assist pressure.
> This is the usual cause of the "brake light on in the morning, goes off 30
> seconds after I start the car" syndrome. A sure sign of this happening is
> the level in the reservoir rising overnight as the car sits.
> 
> The accumulator has nothing to do with the power steering circuit.
> 
> The steering problem is likely caused by low pressure in the steering
> circuit or a sticky spool valve in the rack. The inside of the rubber hoses
> start to break down with age and the little rubber particles clog the
> screens in the banjo bolts and various orfices in the system. A flush of the
> hydraulic system can eliminate the "light on in the morning" syndrome and
> the loss of power steering assist by purging out the rubber particles. If
> your fluid is black instead of clear green you need a flush.
> 
> One important note: these cars are IMPOSSIBLE to stop with no brake assist.
> Your legs just aren't strong enough to generate effective manual braking
> with this system. It is vitally important that the brake assist system be
> kept in good working order.
> 
> HTH
> 
> Fred Munro
> '97 S6
> 
> 
> -----Original Message-----
> From: s-car-list-bounces at audifans.com
> [mailto:s-car-list-bounces at audifans.com] On Behalf Of Jared Robinson
> Sent: June 25, 2009 7:01 PM
> To: s-car-list at audifans.com
> Subject: [s-cars] occasional brake light on start and sometimes difficult
> steering
> 
> So, I was reading some posts about the hydraulic system...
> Once in a while (say once every 2-3 weeks) the brake light stays on for 30
> seconds or less after starting the car. it normally goes away by the time I
> rev the motor...
> Also, sometimes when I'm at the end of my trip and pulling into my spot at
> the train station, I go to turn the steering wheel from a stop and it's VERY
> heavy... almost un-turnable... if I rev the motor, I get plenty of assist
> though... It doesn't do it all the time though, sometimes it does it once a
> week... sometimes twice.
> I saw something about these two problems possibly being related...
> It only really started doing it after I put 17" wheels on the car though. I
> never noticed it with the 15" snow tires.
> 
> What's the story?
> 
> -- 
> Jared Robinson
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