Serious (dangerous) Brake Problems???

[ali@awesome.coronacorp.com (Ali Mouline)]

I once had a similar problem with my 85 5000S. All the brake stuff seemed
to be OK ie. fluid, brake pads etc... but the brake light would come on
once in a while. I then realized that the power stearing fluid was low
(very low). After topping it off the brake light never came on again.
Perhaps you have the same problem ??

Ali Mouline
81 VW Rabbit Diesel
85 Audi 5000S


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>From owner-quattro@coimbra.ans.net Thu Jun 27 16:27 PDT 1996
X-Authentication-Warning: coimbra.ans.net: majordom set sender to owner-quattro using -f
Date: Thu, 27 Jun 96 17:12:11 CDT
From: "P-O Selander" <P-O_SELANDER@ccgate1.exu.ericsson.se>
Encoding: 57 Text
To: quattro@coimbra.ans.net
Subject: Serious (dangerous) Brake Problems???

Hi All,

My brake light has started to "stay" on. Did it in the beginning 
only at low rpms and when breaking, but now it is constant. Lots 
of fluid and the breaks works great. Pads are almost new and all 
disc are in good shape. Car has no ABS.

The honorable Al Powell gave me the following tips (thanks Al):

>Brake light: you can test this, but I'll betcha dinner you need 
>a "bomb".  This is a hydraulic pressure accumulator common to 
>Audi and BMW.  It lives just inside the left front tire well.  
>It's basically a metal bottle shaped kinda like a WWII potato 
>masher grenade (fancy that...).  It contains pressurized 
>nitrogen, and its purposes are to a) damp the pulses from the 
>piston-type hydraulic pump, and; b) store a back-log of the 
>2200 psi pressure the  pump generates, so as to provide a 
>pressure buffer for uses of the brakes and steering.

>Over time, the "bomb" or "PA" loses its pressure, and THEN what 
>happens is your brake light comes on under one or both of two 
>situations: at start-up, it remains on for a while, until 
>pressure pumps up; or, if you hit the brakes two or three times 
>while coasting to a stop and the brake light comes on, you can 
>tell you have lost the buffer.

>The common test is to fire up the car, run it for perhaps 1 min 
>at 1K RPM or more, then shut it off.  Pump the brake pedal and 
>try to "feel" for the number of pumps before the pedal loses 
>its "soft" assisted feel and becomes hard as soon as you press 
>on it.  I personally found this VERY hard to evaluate until I 
>had a good "bomb", but others find it fairly easy to tell.  
>LESS than 10 pumps before the pedal goes hard is NOT 
>acceptable.  A good bomb should do 20 or more. 
>I'll bet you'd be lucky to get 5!

Now after Al's tips and some "roadtesting" I have the following 
to add:

Only get 1-2 pumps before the the pedal looses its "soft" 
assisted feel.
When driving over these small bumpy lane dividers, the light 
seem to go out somewhat.

Once again, the brakes works great. My car is a "beater" to take 
me back and from to work, and I'd like to keep it in shape 
without any major (expensive) repairs.
SO, do I jeopardize SAFETY by not having the "PA" (bomb) 
replaced, or is it more of a "convinience" item for cars with 
ABS (to make for a smoother ABS function)?

Any feedback from you knowledgeable people ot there would be 
great.
------
P-O Selander, Dallas, TX
'89 100E
'91 300 ZXTT



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