200tq Braking Problem

[Darek Jarski]

Based on my friend's advice I proceeded to do a brake fluid flush first, you
know just in case ... the rear brakes aren't getting any fluid what so ever
[completely dry]!!! The line is dry all the way to the ABS module [at least
I think this mysterious box is the ABS module]. I ran out of daylight to
find out if there is any fluid getting to the ABS module from the MC.
Hopefully, it's just a clogged line and I can avoid putting in a new MC.
Have you heard of anything like this? Any advice?

Thanks,
Darek
'89 200tq


>From: Kneale Brownson <knotnook at traverse.com>
>To: "Darek Jarski" <darek_jarski at hotmail.com>
>Subject: Re: 200tq Braking Problem
>Date: Thu, 22 May 2003 17:41:40 -0400
>
>Sounds like your bomb is toast.  TPC has them "on sale" this week, I think
>as one of their specials.
>
>MC is fairly easy:  Just two nuts to take the MC off the booster.  No fancy
>connection in between to worry about.  The most trouble I've had has been
>taking the compression connectors for the lines to the ABS unit out of the
>MC.  The new one should come with new rubber seals for the reservoir.  The
>reservoir just pops out of the MC and back into the new one after that's in
>place.  It's recommended to fill the MC with brake fluid before putting it
>in place because it's sometimes hard to get all the air out of one.  I've
>not done that on the two or three I've replaced and never had any real
>problem, but I use a pressurized bleeder system afterward, so that may be
>why I've not had trouble.
>
>Regards, Kneale
>
>At 01:44 PM 05/22/2003 -0700, you wrote:
>>After shutting down the engine the pedal goes hard on the first pump
>>[after the 3-4" of free play that is]. I just ordered up a new MC from
>>Blau. My main concern is the 3-4" inches of no resitance. It seems
>>excessive. I'm sure it needs a new bomb as well. Any advice on the MC
>>removal and installation?
>>
>>Thanks,
>>Darek
>>
>>>From: Kneale Brownson <knotnook at traverse.com>
>>>To: "Darek Jarski" <darek_jarski at hotmail.com>
>>>Subject: Re: 200tq Braking Problem
>>>Date: Thu, 22 May 2003 16:41:30 -0400
>>>
>>>How many pumps ==after running the engine and then shutting it
>>>down==until you get rock hard pedal?   If it's one to four or five OR
>>>NONE, you need a new bomb ASAP, and that can be causing your vibrating
>>>feel to the pedal, especially at low revs.
>>>
>>>Regards, Kneale
>>>
>>>At 12:45 PM 05/22/2003 -0700, you wrote:
>>>>Thanks for the help. Based on your email, I measured the pedal play with
>>>>the
>>>>car off ... there was about 3-4" of movement toward the floor before ANY
>>>>resistance, at which point I encountered rock hard pedal. Then I started
>>>>the
>>>>car and encountered the same 3-4" of free play followed by a
>>>>pulsating/vibrating hard pedal that went down another inch or two. In
>>>>your
>>>>opinion, am I in for a new MC? Or is there another problem?
>>>>
>>>>Thanks,
>>>>Darek
>>>>'89 200tq
>>>>
>>>>
>>>>>From: Kneale Brownson <knotnook at traverse.com>
>>>>>To: "Darek Jarski" <darek_jarski at hotmail.com>, quattro at audifans.com
>>>>>Subject: Re: 200tq Braking Problem
>>>>>Date: Thu, 22 May 2003 14:58:55 -0400
>>>>>
>>>>>At 11:25 AM 05/22/2003 -0700, Darek Jarski wrote:
>>>>>>Among other issues, my '89 200tq developed a braking problem. I am
>>>>>>getting
>>>>>>deep pulsating pedal feel and loss of braking power [intermittingly
>>>>>>but
>>>>>>progressively worse]. The pedal feels a bit "spongy." There is also
>>>>>>some
>>>>>>free play in the brake pedal. I have a GOO leak in the rack [next on
>>>>>>my
>>>>>>long
>>>>>>list] and possibly a bad bomb, however I thought that loss of
>>>>>>hydraulic
>>>>>>pressure would lead to a stiff pedal [correct?]. I am not losing any
>>>>>>brake
>>>>>>fluid. Could my master cylinder be bad? How do I test it? What else
>>>>>>should
>>>>>>I
>>>>>>look at?
>>>>>>
>>>>>>I am not at all familiar with how the braking system interacts with
>>>>>>the
>>>>>>hydraulic system, so if anyone knows of a good write-up or is willing
>>>>>>to
>>>>>>explain it I would greatly appreciate it.
>>>>>
>>>>>You have a hydraulic brake system where a piston in the master cylinder
>>>>>pushes on fluid that then pushes on calipers at each wheel to clamp the
>>>>>pads onto the rotors.  Behind the master cylinder is a brake booster
>>>>>that
>>>>>amplifies how much pressure your efforts on the brake pedal supply to
>>>>>the
>>>>>piston in the MC.  That brake booster gets its power from the hydraulic
>>>>>pump run off a belt on the front of the engine.  To assure that you
>>>>>have
>>>>>boost even in the event of the engine failing while you're moving,
>>>>>there is
>>>>>a brake pressure accumulator that retains a supply of pressurized oil
>>>>>to be
>>>>>utilized in operating the booster.  If the brake pressure accumulator
>>>>>(fondly referred to as the "bomb" because of both its shape and it's
>>>>>propensity to disgorge its contents explosively if not discharged
>>>>>before
>>>>>being disconnected from its lines) is not functioning properly, the
>>>>>minute
>>>>>the engine stops, you have only the basic hydraulic brake system with
>>>>>no
>>>>>boost.
>>>>>
>>>>>So let's say you have a bad bomb and you push in your clutch so your
>>>>>engine
>>>>>slows while you apply the brakes.  With insufficient RPM's, the
>>>>>hydraulic
>>>>>pump cannot supply the pressure level required to make the booster
>>>>>function
>>>>>as it should, so I'm guessing you may feel the boost varying in the way
>>>>>the
>>>>>pedal feels.  You can test the bomb by turning off the engine and
>>>>>counting
>>>>>the number of pumps on the brake pedal before you feel it stiffen.  A
>>>>>good
>>>>>bomb returns 30 or so pumps.  A poor one maybe 10.  A dead one may give
>>>>>you
>>>>>no pumps.
>>>>>
>>>>>All that said, your description of a mushy pedal sounds like a failing
>>>>>master cylinder.  If, with the engine off, you push on the pedal and it
>>>>>keeps wanting to move toward the floor, that's an indication of failed
>>>>>seals in the MC.
>>>>
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