[s-cars] Brake indicator light

[Tom Green]

The owners manual describes the conditions that make the BRAKE light  
illuminate,
some while braking, some without.

Given the difficulty stopping the car without boost pressure, I think  
they have a note
about driving under these circumstances.  The annoying light and 3  
chimes really do
mean "pay attention".   I assume you have plugged the sensors back in  
after testing
them and cleaning the contacts.  The usual failure mode for the  
sensors is not intermittent
but a steady failure, and you lose the warning protection if you  
leave them unplugged.
This system is no smarter than the operator, hopefully less so. :-)

I agree with Bob's analysis (of course), but thought you would have  
noticed the level in
the reservoir when unplugging the hydraulic fluid level sensor.   
Perhaps the reservoir is
too dirty to see the level?   Or, the filter screen insert is  
restricting flow enough to allow the
float to drop on occasions.  I would only add that the Audi fluid is  
the same as the Pentosin
11S, and the price difference is disappearing.

Let's add an unnecessary note that this Pentosin 11S or Audi power  
steering fluid goes in
the hydraulic reservoir, and the DOT 4 brake fluid is a separate and  
distinctly different fluid
that is added to the master cylinder reservoir.  The only commonality  
is they both have level
sensors that illuminate the BRAKE light when fluid is too low.

I have seen remarkable improvement from cleaning the hydraulic  
reservoir screen and
reservoir and flushing and replacing the fluid.  The procedure is in  
the audifans knowledge
base, except clean the filter screen thoroughly with solvent and  
compressed air.  I don't know
it's minimum particle size but it is very effective and will restrict  
fluid flow when dirty.  If this
flushing procedure is too involved or messy, simply emptying the  
reservoir with a turkey
baster and adding new fluid, drive a few miles and repeat will do  
about the same, just takes
more fluid, and cleaning the filter twice.   Please dispose of the  
used fluid in an environmentally
responsible manner.

Of course, if you have a leak in either the hydraulic boost system or  
the brake system, fix it.

I offer this as a first step to solving braking problems before  
changing some expensive parts,
perhaps unnecessarily.  HTH

Tom




Mark asks:
> Date: Sat, 30 Sep 2006 21:01:06 -0400
> From: "Mark Rivera" <mrivera at webcats.net>
> Subject: [s-cars] "BRAKE" indicator light
> To: "S-Car-List" <s-car-list at audifans.com>
> Message-ID: <KHEHKIJBOCAJPHPCPMNKKEMICLAA.mrivera at webcats.net>
> Content-Type: text/plain;	charset="iso-8859-1"
>
> The "BRAKE" indicator light on my 93' S4 is coming on under medium  
> to heavy
> braking, but nothing severe enough that ABS comes into play.  It  
> goes out
> immediately after I release the pedal.  I may have even seen it  
> come on
> under some corenering situations, not sure.  I've already unplugged  
> the
> level sensor on the fluid reservoir, as well as the 2 wire sensor  
> around the
> master cylinder, whatever that one is.  The light still comes on.   
> I should
> say that the pedal feel isn't that good, and while the brakes work  
> fine
> under light application, anything more than that requires quite a  
> bit of
> effort and pedal travel.  In other words, it doesn't feel linear,  
> and feels
> like the system should be bled.  Is the system smart enough to know  
> that
> something is wrong, or is the light coming on a different, known  
> issue?
>
> Thanks,
> Mark

> Bob offers:
> Date: Sun, 1 Oct 2006 07:57:09 -0400
> From: "Robert Rossato" <bob.rossato_af at cox.net>
> Subject: Re: [s-cars] "BRAKE" indicator light
> To: "'S-Car-List'" <s-car-list at audifans.com>
> Message-ID: <000c01c6e550$b93ced00$e78ec848 at ROSSATO2>
> Content-Type: text/plain;	charset="us-ascii"
>
> This is most likely a low fluid level in your power steering pump
> reservoir level.  The sensor on that reservoir is also tied into the
> brake light.  Top it off and I'll bet you the light stops flashing
> during cornering/braking.  BTDT.
>
> You may still have other issues with your brakes, but the brake light
> coming on during cornering or braking is either a low level in the  
> brake
> fluid reservoir, or the power steering reservoir.  And if you've  
> already
> checked the master cylinder reservoir, then it's the PS one.  You
> probably have a small leak at the top X-plug on the pump.  Use  
> Pentosin
> 11S for the power steering hydraulics.  Don't use anything else.
>
> Bob