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    Lets Talk Caliper Rebuilds

    Probably stupid question. But reaching my wits end chasing this long brake pedal. Started last track weekend with good pedal, first day last session pedal started going long. Second day pedal was long the whole day. Freshly flushed with SRF before the weekend.

    After the track weekend replaced with SS lines and installed brass caliper guide bushings. Flushed with full 1L of bottle of SRF using motive system, MC never ran dry. Pedal still long after this work, feels identical.

    All I can think of to try next is caliper rebuild then MC replacement. I don't think its an MC problem. With the engine off I can pump the pedal and it gets hard. Maybe 1/2 inch of travel before it gets hard. Once you start the engine the pedal travel becomes *very* long. I would think that if the booster was failing then the pedal would get harder not softer.

    Is there an interval everyone uses to replace the square cut seal in the brake calipers? Would a failing square cut seal cause a long brake pedal? I would think that if air was getting past the seal then fluid would also be getting past the seal, right?

    #2
    are your pads brand new? my pedal started getting long in the feel when my pads were past 50% used.
    2018 Grigio Telesto F80 M3 DCT | :: Bone Stock ::
    2004 Titanium Silver E46 M3 6 Speed | :: Track Car ::

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      #3
      Originally posted by sc_tr0jan_m3 View Post
      are your pads brand new? my pedal started getting long in the feel when my pads were past 50% used.
      This is good to know. My HPS on the fronts were at 30% with a soft pedal, reverted back to some random street pads I had on hand and the pedal got much better. To be fair I did bleed the fronts quickly, but didn't observe any air and the fluid was still light yellow.

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        #4
        Originally posted by sc_tr0jan_m3 View Post
        are your pads brand new? my pedal started getting long in the feel when my pads were past 50% used.
        Rears are new. Fronts are 70 percent with a little taper to them.

        If you would estimate how far your pedal travel is with the engine running?

        Before the track weekend the pedal would engage at the same level as the throttle. Now its 2-3 inches below the throttle (this is an estimate I need to actually measure it).


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          #5
          This is another stupid question but, this problem has me doubting my basic understanding of everything .

          When bleeding the brakes, I have a tube around the bleed nipple that goes into a bottle, the tube is submerged in brake fluid. Often times I am bleeding and I will see bubbles in the bottle of fluid and not in the tube itself. I have always assumed that bubbles in the fluid bottle was normal as that is just air that was in the tube being pushed out. Is this correct or incorrect?

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            #6
            The bubbles are being pushed out of the brakes lines while they are being bleed. You want a small hole drilled in your bottle cap for that little bit of air to escape, maybe thats why you are seeing the bubbles in the bottle??
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              #7
              Originally posted by eacmen View Post
              This is another stupid question but, this problem has me doubting my basic understanding of everything .

              When bleeding the brakes, I have a tube around the bleed nipple that goes into a bottle, the tube is submerged in brake fluid. Often times I am bleeding and I will see bubbles in the bottle of fluid and not in the tube itself. I have always assumed that bubbles in the fluid bottle was normal as that is just air that was in the tube being pushed out. Is this correct or incorrect?
              This is correct. The bubbles would come directly out of the nipple into the tube if they were coming out of the brake caliper. I assume you're using a pressure bleeder on the reservoir?
              '03.5 M3 SMG Coupe - Jet Black / Black

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                #8
                Originally posted by r4dr View Post

                This is correct. The bubbles would come directly out of the nipple into the tube if they were coming out of the brake caliper. I assume you're using a pressure bleeder on the reservoir?
                Correct. Pressure bleeder. 20psi


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                  #9
                  Are you sure you don't have air in the system - including ABS?

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                    #10
                    Originally posted by Estoril View Post
                    Are you sure you don't have air in the system - including ABS?
                    Flushed 1L through the whole system. Pretty sure the whole system is 500ml capacity.

                    I did so the ABS bleed as well with foxwell tool.

                    Am I sure? No. But open to ways to be sure.


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                      #11
                      Originally posted by eacmen View Post

                      Flushed 1L through the whole system. Pretty sure the whole system is 500ml capacity.

                      I did so the ABS bleed as well with foxwell tool.

                      Am I sure? No. But open to ways to be sure.


                      Sent from my iPhone using Tapatalk
                      Tey tapping hard on the caliper with a rubber mallet a few times and see what happens. My get quite a few bubbles out. I didn't think it would do anything but I did it on mine and got alot, I was suprised.

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                        #12
                        Originally posted by Icecream View Post

                        Tey tapping hard on the caliper with a rubber mallet a few times and see what happens. My get quite a few bubbles out. I didn't think it would do anything but I did it on mine and got alot, I was suprised.
                        Yup! I always tap on the caliper during the bleeding process.


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                          #13
                          Originally posted by eacmen View Post

                          Yup! I always tap on the caliper during the bleeding process.


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                          Ah. Well then, is it possible your pads are glazed or something? Have you looked at the condition of the pads? Being that it started suddenly at the end of a track day, I would start there or look for a seized piston (though that might have other symptoms too like pulling).
                          When you say pedal goes long, is it actually softer or does it just need to go further to give the same bite?

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                            #14
                            Originally posted by Icecream View Post

                            Ah. Well then, is it possible your pads are glazed or something? Have you looked at the condition of the pads? Being that it started suddenly at the end of a track day, I would start there or look for a seized piston (though that might have other symptoms too like pulling).
                            When you say pedal goes long, is it actually softer or does it just need to go further to give the same bite?
                            That's an excellent question. I want to say it just goes longer to achieve the same bite, still finished the track weekend like that.

                            Our last M3 did not do this but we had ST40 up front. Maybe this is just how the OE calipers behave?


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                              #15
                              Originally posted by eacmen View Post

                              That's an excellent question. I want to say it just goes longer to achieve the same bite, still finished the track weekend like that.

                              Our last M3 did not do this but we had ST40 up front. Maybe this is just how the OE calipers behave?


                              Sent from my iPhone using Tapatalk
                              To me that sounds more like a pad/glazing/worn issue. On mine I have noticed it's just sensitive to good bedding, temp etc. I am not a fan of the OE calipers. I never thought they felt particularly nice (though they are extremely easy to modulate) and after driving a 911 it became even more apparent. I really think you might just end up chasing a ghost. Check the pads for wear/overheating (and pistons for seizing) , replace if necessary and maybe think about a nice BBK in the future.

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