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Re: Serious (dangerous) Brake Problems???

On my urQ, failure of the "bomb" affected transient brake response.  If I
had a reason to stop quickly, the brakes felt dead for an instant, after
which they d**n near locked up I was pushing so hard.  Tough on the laundry

It's a safety item in my books.  Economize on something else.  When you buy
one, check out places like IPC or Carlsen for a good price.

>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
>P-O Selander, Dallas, TX
>'89 100E
>'91 300 ZXTT

Richard Funnell,
San Jose, California
'83 urQ
'87 560 SL