Re: <E28> M5 Brake Light Telltale On!

[Matthew Yip <mgyip@xxxxxxxxxxxxxxxxxxxxxxx>]

John,

I just experienced a similar problem just before ///M Day - high stress factor since I
thought it would keep me from attending with my M5 - it's hard to look "cool" in an F350.

In any case, my problem was very similar and was traced to the pressure switches on the DS
Regulator ( Thanks for the tip Brett).  The two switches (high and low pressure) cost
about $40 and can be replaced for one-six pack and 10 minutes of labor.  If I recall, the
only "trick" is to pump the brake pedal several times to depressurize the system.

As for the slime, it may be that your pressure switches are leaking - mine were.  That
made for a nice mess around the brake booster area!  An indication that da bomb is going
bad is that the "brake" warning light will flash when you step hard on the brakes.  I'll
bet that you're brake warning light flashes indiscriminately, particularly when you
accelerate - not that anyone with an M5 would ever drive irresponsibly.

Hope this helps!

>
> Date: Wed, 18 Nov 1998 06:49:23 EST
> From: Im4BMW@domain.elided
> Subject: <E28> M5 Brake Light Telltale On!(Help)
>
> Fellow Bimmerheads,
>
> I know I don't have an E36 ///M3, Z3, ///M Coupe or Roadster, or other "late
> model" Bimmer, just a "lowly" E28 (they rule you know!)...but I received only
> "one" response to my request for assistance on my brake telltale lighting
> up/ATF loss in the Power Steering reservoir (prior to calling my mechanic).
>
> Please set aside the beers Bubbas and try to help me on this one!!!!!!
>
> My car appears to have a leak somewhere in the power assist for my brake
> system.  The brakes operate "perfectly"..no hard pedal, no travel to the
> floor, etc.  just the dumb brake warning light coming on after the car has
> been driven some...it usually comes on "without" depressing the brake pedal
> even!
>
> I crawled under the car last night to inspect where the ATF fluid is coming
> from and found the underside of the floor pan soaked with something...ATF I
> assume, BUT looking at all the hoses and fittings, including the underside of
> the brake booster and the master brake cylinder, they looked dry as a bone!
> The brake fluid is not leaking either.
>
> The only place that looked wet at all was the brake "bomb" (all grimy on the
> outside surface) and the pressure regulator (grimy too) where the low and high
> pressure switches reside.
>
> If the booster was leaking how could the bomb be all grimy(it resides above
> the booster as you know)?
>
> Is it possible to have a leaking brake accumulator "bomb" that still functions
> well enough that the pedal feels completely normal?
>
> The brake fluid reservoir is "full", and if not for the ATF leak I'd think the
> sending unit on the brake fluid reservoir had gone south.
>
> I would really appreciate some input on this....if it's an easy fix like
> replacing the brake bomb and a couple switches, I'm up to the task, but I
> don't want to fool around with the big $ items like the regulator or the brake
> cylinder(just yet anyway!)
>
> Is anyone up to the challenge?
>
> Thanks to Curt Kiser for responding.  I checked the underside of the brake
> cylinder where the "purge" fitting resides...it looked bone dry to me!
>
> Any help very much appreciated.
>
> John Weese
> Landisville, PA
> BMW CCA #76646
> '73 2002tii
> '88 M5
>
> p.s. Sorry John Allen, I also posted this to the M-Formation Digest since I've
> had so little response from the Big Digest. Regards.
>

- --
Matthew Yip
mgyip@domain.elided

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