[s-cars] A Different Brake Light Question

[chris chambers]

Tom,

I am not familiar with the banjo bolt screens....where are they?


Thanks
Chris

 


----- Original Message ----
> From: Tom Green <TRGreen at comcast.net>
> To: Scarlist <s-car-list at audifans.com>; Douglas Fifield <douglas.fifield at gmail.com>; Fred Munro <munrof at sympatico.ca>
> Sent: Sunday, June 28, 2009 8:31:02 PM
> Subject: Re: [s-cars] A Different Brake Light Question
> 
> Douglas,
> 
>   I would assume you get from 0 to 2 pumps before the pedal is hard  
> after the
> car sits?  If it takes 30 pumps to deplete the accumulator pressure  
> shortly after
> shutdown, then the pump must be supplying pretty good pressure to charge
> the accumulator that well.  Then, pressure is bleeding off during the  
> period the
> car sits.  Have you tried to quantify this time period?  I.e., does  
> the system
> maintain enough pressure so the brake light is out at restart for 1  
> hour?
> 4 hours?  Or, does this brake light not correlate with lack of boost  
> (hard
> pedal)?
> 
> When the brake light is on continuously when hot, can you deplete the  
> brake
> assist pressure by pumping the brakes and get a hard pedal while  
> driving?
> If so, then you have a  problem.  If the brakes and steering operate  
> normally,
> maybe it is a sensor problem.  The sensor of interest is on the brake  
> servo.
> 
> You did not mention fluid appearance or changes but with the work done
> on the system, I have to assume it is fairly new.  It does need to be  
> clean to
> perform up to specs, and all the banto bolt screens need to be clean  
> as well
> as the filter screen in the reservoir neck.  The filter screen is  
> bright metal, not
> black.  That comes from the hoses and pump seals and can severely  
> restrict
> flow and pressure in the system.
> 
> Are there any hydraulic fluid leaks?  Even the smallest seep will  
> deplete the
> stored pressure as well as make a mess where you can't see new problems.
> 
> Tom
> 
> > -----Original Message-----
> > Date: Sat, 27 Jun 2009 14:15:58 -0400
> > From: "Fred Munro" 
> > Subject: Re: [s-cars] A Different Brake Light Question
> > To: "'Douglas Fifield'" ,    "'Scarlist'"
> >     
> > Message-ID: 
> > Content-Type: text/plain;    charset="us-ascii"
> >
> > Douglas;
> >
> > If the light doesn't go off and the reservoir is full, it means that  
> > the
> > brake assist system isn't coming up to pressure. This could be:
> > 1. bad pump
> > 2. leaking brake servo
> > 3. leaking "bomb" bypass valve
> >
> > It could also be a flaky reservoir level sensor or emergency brake  
> > sensor,
> > but that doesn't sound likely from your description of the symptoms.
> >
> > 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 Douglas Fifield
> > Sent: June 27, 2009 1:40 PM
> > To: Scarlist
> > Subject: [s-cars] A Different Brake Light Question
> >
> > Gents,
> >
> > I also am having brake light problems.  Patient is a 95.5 S6 Avant
> > with about 140K miles on the clock.
> >
> > Symptom is a brake light that stays on too long when cold starting and
> > sometimes does not go off at all when engine is fully warmed in hot
> > weather.
> >
> > Pentosin reservoir is full (even a little over) when engine is
> > running.  Braking feels normal - no pulsing of the pedal.  With engine
> > off, I got about thirty pumps of the pedal before it went hard.
> >
> > I replaced the brake servo two years ago with a new unit.
> >
> > I was leaning toward a bad bomb before doing the pump-down test.
> > What's left?  The pump?
> >
> > Looking for wisdom in Minnesota.
> >
> > -- 
> > Douglas in MN
> > 95.5 Audi S//6 Avant
> > 73 BMW R60/5 mit Toaster Tank
> 
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