testing rear master cylinder

Discussion in 'Wheels' started by nascar7613, Jan 26, 2009.

  1. nascar7613

    nascar7613 Active Member

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    Is there a method for testing the rear master cylinder on a 98 Dyna? I'm not sure if the master cylinder is bad or if there is air trapped in the system, but I can't get the rear calipers to pump up. I have a vacuum pump and it draws air and fluid through, but it will not get to the point where it is fluid with no air. Thanks.
     
  2. kemo

    kemo R.I.P

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    If you pull back the boot over the push rod and see that it is wet then you know that the M/C seals are leaking and the fluid is bypassing the seals.
     
  3. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    Gotta '91 Dyna. I suggest just getting the guts (rebuild kit) and changing it out. Not too expensive and easy to do. Then you can flush the system well with some new brake fluid (mine uses DOT 5, and I suspect so does yours).

    With your vacuum, you can drag out all the trapped air and should have some good firm pedal!!

    TQ
     
  4. nascar7613

    nascar7613 Active Member

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    I think you're right. Thanks for the advise.
     
  5. glider

    glider Veteran Member

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    Check the DOT on your fluid, the 07 may be using dot 4, they switched over previous to 07.