Re: Warning Lights

["Fred Munro" <munrof@isys.ca>]

The bomb is a black steel cylinder with hemispherical ends located inboard
of the left front wheel. It contains a rubber diaphragm and is pressurized
on one side of the diaphragm to around 4000 psig with nitrogen (hence the
name "bomb"). Hydraulic fluid flows into the other side of the bomb and this
provides a reservoir of 4000 psig fluid for brake boost when the engine is
off and the hydraulic pump is not running. With time, the nitrogen seeps
through the diaphragm into the fluid and the bomb loses it's pressure
(around 7 years).

The check procedure is as follows:

1. Run the engine until the red brake warning light goes out (this means the
hydraulic system is up to pressure)

2. Shut off the engine. Repeatedly apply the brakes. The brake pedal will
depress easily while hydraulic pressure is available for boost, but will
become harder to depress when the bomb is discharged and boost is no longer
available.

3. Count the number of brake applications you get before the pedal gets
hard. If you get less than 10, replace the bomb. A new bomb gives 30 - 40. A
dead bomb will not even give 1. An alternative is to turn the ignition on
and pump the brakes until the red brake light comes on, indicating low
pressure.


Fred Munro
'91 200q  281k km


----- Original Message -----
From: Livolsi, Stephane <livols1@investorsgroup.com>
To: 'Fred Munro' <munrof@isys.ca>
Cc: 'Audi Quattro List' <quattro@audifans.com>
Sent: Thursday, September 30, 1999 12:11 AM
Subject: RE: Warning Lights


> how do you "check" the bomb, and where is it?
> Stephane Livolsi
> 180 Yorston St
> Williams Lake, BC, V2G 3Z1
> ph 250-392-2637
> fax 250-392-2693
>
> '86 5KTQ stock (if you don't know what it means, you aren't in the club)
>
> >----------
> >From: Fred Munro[SMTP:munrof@isys.ca]
> >Sent: September 29, 1999 7:08 PM
> >To: Christopher Ritchie; quattro list
> >Subject: Re: Warning Lights
> >
> >Hi Christopher;
> >
> >    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.
> >
> >    As you learned first hand, our cars drive around quite nicely with a
bad
> >bomb until you really need the brakes. Take note of Christopher's BTDT,
> >folks. If your bomb is over 7 years old, it is probably bad. Check it and
> >replace it!
> >
> >Fred Munro
> >'91 200q  281k km
> >
> >----- Original Message -----
> >From: Christopher Ritchie <cjr1@gte.net>
> >To: quattro list <quattro@audifans.com>
> >Sent: Wednesday, September 29, 1999 7:43 PM
> >Subject: Re: Warning Lights
> >
> >
> >> Fred Munro wrote:
> >>
> >> >Driving the car with a bad bomb or with low hydraulic pressure is
> >> >dangerous. You will rapidly run out of brake assist in a panic stop,
> >> >significantly increasing your braking distance (and resistance!).
Unless
> >> you
> >> >have the legs of a power lifter, it is a very good idea to keep the
brake
> >> >assist system in good working order.
> >>
> >>
> >> I wholeheartedly agree.  I drove around for awhile with a bad bomb.
The
> >> brakes worked fine in normal braking and I reasoned that I could
> >compensate
> >> for a hard stop.  _WRONG_  Almost soiled myself when someone pulled out
in
> >> front of me too close.  When you step on the brake pedal hard and
> >suddenly,
> >> it will not result in the instant braking action you expect.  It will
take
> >a
> >> few milliseconds for you to realize what is going on.  Then you will
> >> compensate by standing on the pedal.  But those few milliseconds will
seem
> >a
> >> lot longer when danger is imminent.  That, plus the braking distance
will
> >be
> >> longer.  I don't remember if the ABS engaged.
> >>
> >> I replaced my bomb at the next available opportunity.
> >>
> >>
> >
> >
>