Brake pedal pulsates to floor

[munrof at sympatico.ca]

Hi Scott;

I don't think your problem is ABS - ABS will pulsate the pedal, but you'll hear a lot of noise and the pedal won't go to the floor.
My guess is it involves the hydraulic assist system since it only happens when the engine is running. The pulsation you feel is probably caused by the pressure pulses from the hyraulic pump. This would lead me to believe your bomb may be bad, so you may want to do the bomb test.
Under assist, the pedal will drop a lot further than with no assist, but if it is going to the floor, your master cylinder may be leaking. Did you pump the brakes to bleed them or did you use a pressure bleeder? When you pump brakes to bleed them, the master cylinder piston travels beyond it's normal stroke and if there is crud built up on the walls it can score the seals, resulting in a slow leak.
Just guesses on my part - I've never personally had this problem.

HTH

Fred Munro
'94 S4
>
> From: "scott miller" <macatawa at hotmail.com>
> Date: 2001/11/17 Sat AM 03:49:11 EST
> To: quattro at audifans.com
> Subject: Brake pedal pulsates to floor
>
> I emptied my reservoir in this brake job, then bled the brakes thoroughly.
> Now when I push hard on the pedal, it pulsates as it moves to the floor.
> Firm pressure is normal, brakes felt good on test drive.  With the engine
> off, the pedal will not go to the floor.  No warnings on autocheck.  Feels
> like an ABS problem.  Day 3 of a simple caliper change, I'm too tired to
> think, my wife is showing me car ads and I'm starting to look.  What did I
> break now?
>
> Scott Miller
> '90 200qa
> Holland, MI
>
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