RE: Warning Lights

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

>     I can bet that your ABS did not engage, because without a 
> bomb full of
> pressurized fluid, there is nothing to power the ABS system! 
> From what I
> understand, when the ABS activated, it uses up a lot of 
> pressure in a hurry,
> and without a charged bomb the pump can't keep up to the demand.

No ... the ABS system has its own pump ... it makes no assumptions about the
steering/brake assist hydraulic system.  If you think about it the working
fluid that the ABS system operates in is the DOT-3/4 brake fluid, not the
ATF/Pentosin fluid that the "bomb" deals with.  

IME, while the ABS probably did not activate right away, it might well have
after a short while.  This is precisely my motivation for stating in my
earlier post that a bad bomb should be replaced ASAP.  IMO it is less of an
issue on ABS-equipped cars because the ABS can kick in to prevent you from
locking up all 4 wheels.  

On my QTC (no ABS) when it had a bad bomb in panic stop situations it was
quite apparent that extraordinary brake pedal pressure was needed to stop
the car in time.  The hydraulic pump was not able to supply the immediate
need by itself, but it was still pumping, so after a second or so the assist
starts to increase.  Given the amount of pressure that is being applied to
the pedal due to no assist the wheels will start to lock up.  Where you may
have been at the threshold point w/o assist now you have to consciously back
off the pressure on the brake to get back to that point now that you have
assist ... and if you don't react quickly the wheels could lock up and the
car may become uncontrollable.  If you are in a panic stop situation it is
likely that you have other things to deal with besides braking, so this can
divert some attention to these things.  

A car with ABS will still have the initial OH $#&*! when you realize that
you need to push harder than you expected to stop the car in time ...
deinitely a safety issue, but at least you can count on the ABS keeping you
from losing control when the boost comes in.  Hey, perhaps Daimler-Chrysler
(I love calling them that!) got the idea for their braking system that
applies the brakes more than you after driving an Audi with a bad bomb ...

Steve Buchholz
San Jose, CA (USA)

BTW Stephane, I believe that on your car the bomb is mounted behind the
radiator and in front of the front wheel.  You can probably see it by
looking at the car from underneath.  The PA got the name "bomb" fom its
appearance on some of the older cars (I'll have to take a picture of the
original unit from my QTC and put it on a website), but on your car the PA
will look like a elongated casting with a somewhat spherical distention on
one end and a few hydraulic lines attached.