[s-cars] abs purge procedure

[Mike Fitton]

Okay...

I have a 95.5 S6, which does include EDL functionality.  I'm trying to 
diagnose a soft pedal by eliminating one thing after another.  I think 
the pressure accumulator's okay, and I replaced and bled the brake fluid 
right after I got the car about six months ago with no change in the 
pedal.  I know I haven't checked everything yet, but I'm one of the 
20ish guys on here that are planning on a brake upgrade in the near 
future.  (Thanks to all involved for that, btw.)  Since I'll be 
replacing and bleeding for that once again, I thought I could maybe 
manually bleed some ABS hardware.  I didn't know there was a software 
option for it.  But I have no reason to believe the ABS controller was 
ever replaced...so does that mean the possibility of there being air in 
it is extremely slim?

Another suspicion is a physically moving master cylinder.  First heard 
about that on A8s, then noticed the same thing on my buddy's A4 last 
night.  I'll probably check that out on my car in the next hour 
sometime.  Then there's the possibility of an internally leaking MC or 
prop valve or something as well.  Something that leaks, but doesn't drop 
fluid on the ground...

If I decide that I need a new MC, is there a bigger one that's a direct 
or easy swap?

-Cheers!
Mike

Keith Maddock wrote:
> I'll second Bob's procedure, we often due this in a pinch when working
> on an early prototype unit which doesn't have a electronic controller
> with a functioning bleed routine in the software.
>
> Though the question is why you need to bleed the ABS controller - the
> only time you should really need to do this if the unit has been
> disconnected.
>
> If this is the case, I advocate (as Bob mentions) a very very thorough
> bleed of the brakes before activating the ABS unit for several stops,
> and then another thorough bleed.
>
> This of course is easier said when you're not paying for the labor
> time and when you have brake fluid siting around in 55 gallon
> drums....
>
> This becomes more complicated for ABS units which also contain
> Brake-TC (EDL) or ESC (DSC / ESP) functionality.  In this case you
> really need to use the diagnostic-activated bleed routine .
>
> Cheers,
> Keith
>
> On 12/17/06, Robert Rossato <bob.rossato_af at cox.net> wrote:
>> This is the procedure using VAG-COM, but I'm not sure if it will work on
>> our cars.  May be for the C5 chassis and beyond.
>> http://www.ross-tech.com/vag-com/cars/absbleeding.html
>>
>> The other thing you could do is bleed the brakes by your preferred
>> method.  Then go out on a straight deserted road and stand on the brakes
>> hard enough to activate the ABS.  Do this a couple of times and then
>> rebleed the brakes.
>>
>> Bob
>>
>> > -----Original Message-----
>> > From: s-car-list-bounces at audifans.com
>> > [mailto:s-car-list-bounces at audifans.com] On Behalf Of Mike Fitton
>> > Sent: Saturday, December 16, 2006 5:27 PM
>> > To: S Car List
>> > Subject: [s-cars] abs purge procedure
>> >
>> >
>> > I swear I read somewhere about a procedure to purge/flush the ABS
>> > system.  I looked through the archives for the last six
>> > months or so and
>> > on SJM and didn't run across it.  Anyone know where it is or
>> > how it goes?
>> >
>> > -Cheers!
>> > Mike
>