[s-cars] abs purge procedure

[Robert Rossato]

Well, as we all know the North American models of the UrS4/6 have fairly
soft brakes to begin with.  However, one thing I've noticed that will
dramatically improve the feel of the brakes is new rear rotors and pads.
What shape are your rear brakes in?  Even if they have a decent amount
of pad material left, they will feel much better with new pads & rotors.
For whatever reason they definitely do not stay firm throughout their
pad life.  It may be due to corrosion build-up on the caliper carrier
where the pads slide.  It might have a tendency to push the pads back
when they're thinner.  I always wire brush that area to get rid of all
scale and add a little anti-seize.

And then of course there is the flexure of the front G60s, which it
sounds like you're already planning on replacing.

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: Sunday, December 17, 2006 2:27 PM
> To: keith at maddock.com
> Cc: Robert Rossato; S Car List
> Subject: Re: [s-cars] abs purge procedure
> 
> 
> 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
> >
> 
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