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  • Vibration in the brake pedal

    Hello,

    I have a vibration in the brake pedal even when the car is not moving. The vibration seems to come from the hydraulic circuit as it’s vibrating too.
    I have replaced the hydraulic pump but unfortunatly, the problem remains.

    Also, not knowing if it’s the consequence or a possible cause, the ABS can start to work at very low speed (max 10km/h)

    I have no defaults in the monotronic.

    any idea ?

    Thanks


  • #2
    Checked for fault codes in the ABS unit?

    Comment


    • #3
      This is a sign of either the hydraulic servo failing, or the bomb completely gone. Does it vary with engine speed?

      Either one is a big bill, and don't seem to last, so I went with a late model cabriolet vacuum servo, and a refurbed PAS pump from Error404 and not had a problem since

      Comment


      • #4
        Thanks for your answers.

        The vibration vary with the engine speed yes. The pump have just been replaced by a refurbished one without change.

        I have no fault in the ABS unit.

        Someone told me that it can be caused by a special pipe in the hydraulic system... But I don't know more

        Comment


        • #5
          I think, I'm having the same problem so will be observing this topic .Already changed servo for refurb one swapped pas pump and brake bomb and still the same. Dont want to go vacuum route

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          • #6
            Seriously? Nobody?

            Comment


            • #7
              The brake bomb is a possible culprit. Have you tested how many pumps you get before the brake pedal goes solid with the engine off?
              Greg

              S2Forum.com Administrator & Webmaster

              '93 Coupe with a few tweeks

              Comment


              • #8
                If you've changed all three you either have a faulty new component or a ghost in the system -theres nothing else to it to be honest.

                Comment


                • #9
                  Have the same problem, it was the brake booster, behind master cylinder

                  Comment


                  • #10
                    Yup, I think that was where my problem was before going vacuum.

                    Comment


                    • #11
                      Here is the solution to my problem : it was caused by a valve in the hydraulic system. The valve is plugged on the steering rack. Reference 8E0422529, 5.22€... Still available in the VW/Audi network.

                      See https://www.ecstuning.com/b-genuine-...olt/8e0422529/
                      Or http://www.oemepc.com/audi/part_sing...rt_id/0/lang/d

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                      • #12
                        This “fix” can only be coincidental. The brake assist and steering are completely independent hydraulic circuits. Highly likely you had contaminated fluid and a blocked gallery in the brake servo or blocked check valve in the brake bomb.
                        The check valve in the rack has zero effect on the braking circuit, in fact that check valve is not even used on servotronic or older racks.
                        Panthero Coupé quattro 20vt
                        Indigo ABY coupé
                        Imola B6 S4 Avant

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                        • #13
                          I fixed mine with a new booster as well!

                          Comment


                          • #14
                            Originally posted by Error404 View Post
                            This “fix” can only be coincidental. The brake assist and steering are completely independent hydraulic circuits. Highly likely you had contaminated fluid and a blocked gallery in the brake servo or blocked check valve in the brake bomb.
                            The check valve in the rack has zero effect on the braking circuit, in fact that check valve is not even used on servotronic or older racks.
                            See this : http://forums.quattroworld.com/s4s6/msgs/25095.phtml

                            The valve was creating a vibration in the whole hydraulic circuit. I changed only that and it was the last option before changing the bomb. Of course I lost a bit of oil, but less that when I have changed the pump.

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