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Brake Master Cylinder

Discussion in 'Mondial' started by cockrill, Apr 21, 2015.

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  1. cockrill

    cockrill Formula 3

    Jan 23, 2008
    1,088
    Columbia, MO
    Full Name:
    Jeremy Cockrill
    #1 cockrill, Apr 21, 2015
    At stoplights my Mondial's brake pedal will slowly sink to the floor. A quick little pump will bring back the pressure, but I think that it's time to rebuild or replace the Brake Master Cylinder. (I cannot find any brake fluid leaks and I do not think I have air or water in the system, which pretty much leaves the Brake Master Cylinder as the culprit.) It looks like replacement Brake Master Cylinders are around $400, whereas a rubber seal kit (from SuperPerformance) is less than $50.

    Has anyone rebuilt or replaced their BMC? Is it worth trying just replacing the seals?

    Thanks!
     
  2. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    37,106
    Cowboy Capitol of the World
    Full Name:
    Brian Crall
    #2 Rifledriver, Apr 21, 2015
    As a matter of liability, most businesses just install new. As far as rebuilding there is a very good chance the bore of the cylinder is not in good enough condition to just replace the rubber.

    Take it apart and have a look. Then decide.
     
  3. MvT

    MvT F1 Rookie

    May 25, 2013
    4,261
    The Netherlands - NH
    Full Name:
    Tijn
    #3 MvT, Apr 21, 2015
    I think you have an internal leak. It's an easy one to rebuild. Depending on the state you would need to hone the cylinder. The rubber seals (cups) are Fiat sizes so I would first go to a local shop. I paid 10 bucks for 2. Let me see if I can dig up some pics tonight.
     
  4. cockrill

    cockrill Formula 3

    Jan 23, 2008
    1,088
    Columbia, MO
    Full Name:
    Jeremy Cockrill
    #4 cockrill, Apr 24, 2015
    Thanks, guys, for the responses. I ordered a new set of rubbers from Superformance. If replacing the gaskets doesn't fix the issue I'll order a new master cylinder. (Brian, thanks for the heads-up to take a close look at the bore.)

    I'll take lots of pictures of my rebuild attempt and post them here.
     
  5. MvT

    MvT F1 Rookie

    May 25, 2013
    4,261
    The Netherlands - NH
    Full Name:
    Tijn
    #5 MvT, Apr 24, 2015
    Sorry Jeremy, I've got no pics of my rebuild. I'm stunned as I actually take pics of all the things I touch.

    You might need to hone it a bit. This is the honing device. Your local car part should have it as they come in different sizes. Put it on an electric screwdriver and off you go!

    Just to get the idea.
    Amazon.com: Lisle 10500 Brake Cylinder Hone: Automotive
     
  6. 123howie

    123howie F1 World Champ

    Jul 3, 2014
    16,017
    El Segundo CA
    Full Name:
    Howie
    #6 123howie, Apr 24, 2015
    $400 sounds cheap to me, compared to other parts?
     
  7. Nathan76

    Nathan76 Formula Junior

    Jun 20, 2013
    344
    Leicestershire, UK
    #7 Nathan76, Apr 24, 2015
    I had this exact problem. System drained new bleed nipple fitted and new fluid added and system bled properly. And the pedal is now solid.
     
  8. Rapalyea

    Rapalyea Formula 3

    Jun 18, 2013
    1,511
    Georgia Mountains US
    Full Name:
    David Rapalyea alias
    #8 Rapalyea, Apr 24, 2015
    DISRGARD THE FOLLOWING POST. It refers to the CLUTCH master cylindar. But I am leaving the discussion just incase anyone else needs to remove the clutch master.

    [Have you removed the master cylindar? I did it twice and I would PAY $500 for someone else to do it in the future. If you have not done it yet here is how I did it. First, there is a big black spring in the way. I do not have and could not find a tool to stretch and remove it. That would be the best thing.

    I bought a pair of 12 inch needle nose plyers with a 90 degree bend at the top. Then I just grabbed hold of the cotter key that holds the connector piece in place and just forced it out with vigorous twisting. Then I pushed the connector piece up out of the yoke but it would not push up enough to clear the metal sheet above. So used same plyers to man-handle it out of the top.

    But that meant there was no reasonable way I could expect re-insert it the same way. So I put it in upside down and used a self-locking cotter key on top. Needed to poke around endlessly to find the cotter key hole, but was able to do it.]
     

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