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Weeping big brake master cylinder resrevoir cap.

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    #1

    Weeping big brake master cylinder resrevoir cap.

    I have a 98 to 02 master cylinder on my big brake swapped 1987 crown vic.

    My master cylinder cap is leaking very little fluid every time I drive it.

    I have already replaced the gasket with a new "help" item and it is doing the same thing. No better and no worse.

    The master cylinder reservoir is not over filled and only slightly weeps down the side and sits on the lip of the reservoir.

    What gives?

    I am tempted to cut a thin piece of rubber and sip that behind the main gasket in the cap to get more seal out of things?

    Suggestions? Thoughts?
    ~David~

    My 1987 Crown Victoria Coupe: The Brown Blob
    My 2004 Mercedes Benz E320:The Benz

    Originally posted by ootdega
    My life is a long series of "nevermind" and "I guess not."

    Originally posted by DerekTheGreat
    But, that's just coming from me, this site's biggest pessimist. Best of luck

    Originally posted by gadget73
    my car starts and it has AC. Yours doesn't start and it has no AC. Seems obvious to me.



    ​
    Tags: None
    #2
    Wonder if the cap itself is warped/damaged? If the gasket is good (?) then it must be the cap or reservoir surface itself. Can you run a metal ruler over the reservoir surface to check for uneven surface? This is an interesting problem - now I'm curious!
    What I Own: 1993 Mercury Grand Marquis GS
    What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

    Comment

      #3
      I know Mustangs have this issue and the fix there is to lower the fluid level a bit.

      Check the surface of your master cylinder where the cap sit and make sure that it's level. I've seen aftermarket cylinders where the surface wasn't level and it was leaking. Might have to take a file to it to level it out.

      Comment

        #4
        For your rear brakes, Are you running drums or disks? I think the 98 to 02 master would be set up for a disk/disk system. Don't know if this would cause your leaking problem.


        88 Country Squire
        86 Colony Park, non-op'd
        89 Mark VII LSC, non-op'd

        Comment

          #5
          Originally posted by friskyfrankie View Post
          Wonder if the cap itself is warped/damaged? If the gasket is good (?) then it must be the cap or reservoir surface itself. Can you run a metal ruler over the reservoir surface to check for uneven surface? This is an interesting problem - now I'm curious!
          I will have to check for flatness. In my head either the cap or reservoir surface itself is worn out/damaged in a way to create this weepage.

          Originally posted by Mr Bean View Post
          I know Mustangs have this issue and the fix there is to lower the fluid level a bit.

          Check the surface of your master cylinder where the cap sit and make sure that it's level. I've seen aftermarket cylinders where the surface wasn't level and it was leaking. Might have to take a file to it to level it out.
          This was not always the case with the car. Seemed to only start after the 5 speed swap. Only thing that comes to mind is that the fluid now gets more thrown around while banging gears......

          Originally posted by tikitiki65 View Post
          For your rear brakes, Are you running drums or disks? I think the 98 to 02 master would be set up for a disk/disk system. Don't know if this would cause your leaking problem.
          Good observation. I failed to mention that I also have rear discs on the vehicle in question.
          ~David~

          My 1987 Crown Victoria Coupe: The Brown Blob
          My 2004 Mercedes Benz E320:The Benz

          Originally posted by ootdega
          My life is a long series of "nevermind" and "I guess not."

          Originally posted by DerekTheGreat
          But, that's just coming from me, this site's biggest pessimist. Best of luck

          Originally posted by gadget73
          my car starts and it has AC. Yours doesn't start and it has no AC. Seems obvious to me.



          ​

          Comment

            #6
            haven't had that on mine, but it could have some plastic flash around the opening or something

            just watch what sort of rubber you use. Lots are not compatible with brake fluid and will turn into a swollen mushy mess.
            86 Lincoln Town Car (Galactica).
            5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

            91 Lincoln Mark VII LSC grandpa spec white and cranberry

            1984 Lincoln Continental TurboDiesel - rolls coal

            Originally posted by phayzer5
            I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

            Comment

              #7
              Originally posted by gadget73 View Post
              haven't had that on mine, but it could have some plastic flash around the opening or something

              just watch what sort of rubber you use. Lots are not compatible with brake fluid and will turn into a swollen mushy mess.
              True. Even a thin nylon, plastic etc would suffice to use as a shim up under the primary gasket.....

              I'll have to give it a real good look to see whats up.
              ~David~

              My 1987 Crown Victoria Coupe: The Brown Blob
              My 2004 Mercedes Benz E320:The Benz

              Originally posted by ootdega
              My life is a long series of "nevermind" and "I guess not."

              Originally posted by DerekTheGreat
              But, that's just coming from me, this site's biggest pessimist. Best of luck

              Originally posted by gadget73
              my car starts and it has AC. Yours doesn't start and it has no AC. Seems obvious to me.



              ​

              Comment

                #8
                Great thread good info thanks
                ..

                Comment

                  #9
                  plastic would probably work. Got an old brake fluid bottle to cut up?
                  86 Lincoln Town Car (Galactica).
                  5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                  91 Lincoln Mark VII LSC grandpa spec white and cranberry

                  1984 Lincoln Continental TurboDiesel - rolls coal

                  Originally posted by phayzer5
                  I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                  Comment

                    #10
                    Yes! That is a good idea...It holds brake fluid after all.

                    I did cut two thin spacers up out of some thin plastic already and will try those out with a different cap and gasket I have on hand after inspecting the caps mating surface on the reservoir.
                    ~David~

                    My 1987 Crown Victoria Coupe: The Brown Blob
                    My 2004 Mercedes Benz E320:The Benz

                    Originally posted by ootdega
                    My life is a long series of "nevermind" and "I guess not."

                    Originally posted by DerekTheGreat
                    But, that's just coming from me, this site's biggest pessimist. Best of luck

                    Originally posted by gadget73
                    my car starts and it has AC. Yours doesn't start and it has no AC. Seems obvious to me.



                    ​

                    Comment

                      #11
                      Checked out the reservoir mating surface and it is all smooth. While rubbing my finger around the mating surface I can feel a slight dip in a spot or two but it is a very smooth dip.

                      I had another cap and gasket which I slipped a thin plastic spacer behind the gasket and will see how it goes.

                      Definitely a lot tighter going on now.

                      The picture below shows how wet the top gasket gets.

                      Pulling the gasket out revealed just as much fluid.

                      I believe it was just not a good seal causing the fluid to slip around the gasket and then drip out of the cap.

                      I will update when there is an update.

                      Attached Files
                      ~David~

                      My 1987 Crown Victoria Coupe: The Brown Blob
                      My 2004 Mercedes Benz E320:The Benz

                      Originally posted by ootdega
                      My life is a long series of "nevermind" and "I guess not."

                      Originally posted by DerekTheGreat
                      But, that's just coming from me, this site's biggest pessimist. Best of luck

                      Originally posted by gadget73
                      my car starts and it has AC. Yours doesn't start and it has no AC. Seems obvious to me.



                      ​

                      Comment

                        #12
                        I think this is good now. No weepage after this last 250+ mile outing.
                        ~David~

                        My 1987 Crown Victoria Coupe: The Brown Blob
                        My 2004 Mercedes Benz E320:The Benz

                        Originally posted by ootdega
                        My life is a long series of "nevermind" and "I guess not."

                        Originally posted by DerekTheGreat
                        But, that's just coming from me, this site's biggest pessimist. Best of luck

                        Originally posted by gadget73
                        my car starts and it has AC. Yours doesn't start and it has no AC. Seems obvious to me.



                        ​

                        Comment

                          #13

                          Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
                          rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

                          Originally posted by gadget73
                          ... and it should all work like magic and unicorns and stuff.

                          Originally posted by dmccaig
                          Overhead, some poor bastards are flying in airplanes.

                          Comment

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