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    Hard brake pedal after coasting downhill?

    On my trip home from work I drive down a rather steep, twisty road for maybe 1/4 - 1/2 mile. I often engine brake down the hill in 3rd gear, and when I get to the bottom and hit the brakes the pedal is really hard. Anyone know why it would do that? I have braided steel lines and don't use the wear sensors, but aside from that the system is stock.

    Thanks
    sigpic
    1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN

    WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack

    #2
    sounds like a vaccum issue, brake booster isnt getting enough vaccum to operate correctly.
    IG: @Baye30

    FRONT VALENCE IS ZENDER!!! STOP FILLING MY PM BOX PPL!!!

    Comment


      #3
      Engine braking should create lots of vacuum. I do agree on the brake booster, but I'm thinking it's damaged internally, possibly has fluid inside.

      Is it a solid feel, or squishy?
      Does the problem go away immediately, or take awhile?

      Comment


        #4
        Replace the check valve on the booster.
        2006 GMC Sierra 2500HD 4WD LBZ/Allison
        2002 BMW M3 Alpinweiß/Black
        1999 323i GTS2 Alpinweiß
        1995 M3 Dakargelb/Black
        - S50B32/S6S420G/3.91
        1990 325is Brilliantrot/Tan
        1989 M3 Alpinweiß/Black

        Hers: 1996 Porsche 911 Turbo Black/Black
        Hers: 1988 325iX Coupe Diamantschwartz/Black 5spd

        sigpic

        Comment


          #5
          When the pedal goes hard it goes HARD. Tap it a couple times it comes right back to normal. Otherwise the brakes work GREAT, among the best of any car I've owned.

          I suppose I'll start with the check valve and if that doesn't do it replace the booster down the road. Only seldom is it an issue so I'm not too worried as long as it doesn't get worse.

          Thanks guys.
          sigpic
          1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN

          WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack

          Comment


            #6
            Did you figure it out?

            Comment


              #7
              No, I haven't messed with it further. Its only a very occasional issue, I don't recall it happening in a while, and the car has more pressing issues being taken care of at the moment.
              sigpic
              1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN

              WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack

              Comment


                #8
                OP;

                I am having somewhat of the same issue, but instead, my brakes become stiff after constant pressure -with the most noticeable resistance at 1/2 or less of normal pedal travel when braking, which results in reduced braking force. Once I relieve pressure and tap, braking is improved until full pressure applied again and the symptom re-occurs.

                I have done the following:

                replaced booster
                replaced master cylinder
                replaced check-valve
                actuated ABS on wet roads
                ..and bled brakes at least a dozen times.

                All with no help. Still tinkering with this (and my transmission popping out of 1st)

                Keep us posted.

                Thanks!
                ********
                1989 325i w/o 4/14
                1991 318is
                1991 325i

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