Manual Brake Push Rod

Discussion in 'Technical' started by Renton5, Jun 3, 2021.

  1. Renton5

    Renton5 Member

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    Hi Everyone!
    I have a '71 Mav, 200 engine, manual brakes.
    I'm doing a full brake job on it, replacing everything except the steel lines
    and the brass junctions.
    I got a Raybestos Master Cylinder. It came with two push rods--6 1/4, and 6 1/2.
    I was thinking of comparing the length of the rod in the old M.C., then use
    the matching rod in the Rayb unit. I've seen a video on removing the push rod
    from the M.C., it required the unit to be put into a vice and using some force, the
    rod came out. I don't have a vice. All I can say about the old M.C. is that is says,
    Made in U.S.A. on it. I don't know if that means it's the original, or just a
    replacement from when they were made here.

    I was thinking that even if I did get the old rod out, and one of the two new
    rods was a match, that still doesn't mean that the new M.C. has the same rod
    placement depth in the unit as the old one.

    Should I just make a random choice and hope that the 1/4-inch difference--if I
    choose incorrectly, isn't something my foot will notice when coming off the gas pedal?

    Also, when looking at the rod on the old M.C., I pulled back the rubber boot, and some
    fluid came out. Does this mean that a seal was bad?

    Thank you very much!
    Bye,
    Daniel
     
  2. mojo

    mojo "Everett"- Senior Citizen Supporting Member

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    If fluid came out of boot seal is bad. I replaced my mc yesterday and have two new rods, if I don’t forget, will measure them tomorrow let you know what I get. Maybe someone will get in here b4 and give you the information .
     
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  3. Renton5

    Renton5 Member

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    Thank you for your response!
    I've had a feeling there was something wrong with the mc for some time--I'm
    very glad to be replacing that--along with everything else!
     
  4. Krazy Comet

    Krazy Comet Tom

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    Orig master cylinders were painted black, almost none have survived 50ish years. usually repl every 15 years or so.

    As you already know rods are retained by a clip. Put it together without the clip, if pedal is too high use the shorter one, too low, longer.

    I did just that on my Fairlane, first one seems to be OK, never installed clip. Yes it had it's original black painted MC.
     
  5. ADOR

    ADOR Member

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    On The 72 Comet GT I just sold I did a disk brake upgrade and got a later model manual disk master to go on it. (It was originally manual Drum) I used the provided new rod even though it was a tad longer. It worked but kept the pedal up too high. I wound up having to swap back to the old rod length.
     
  6. TeeEl

    TeeEl Member

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    Use the shortest rod of the three...
     
  7. Renton5

    Renton5 Member

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    Hi Mojo, Krazy Comet, ADOR, and TeeEl!
    Thank you all for your help and suggestions!
    I will try the trick with putting an unclipped rod in to check the
    pedal length. I have a feeling that the shorter rod will be the right one.
    I may try to pull out the rod in the old MC to check the length--since
    the unit is bad, I can't break it!

    I decided to replace the wheel cylinder bolts--the ones that go through
    the backing plate. They're a bit rusty, and I rounded the corners of one
    of them while tightening it. These are the smaller diameter bolts, used
    for the small engine cars. Does anyone know where I might be able to
    get them?

    Bye,
    Daniel
     
  8. Krazy Comet

    Krazy Comet Tom

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    Wheel cylinders are same for 6 & V8. Most any hardware store should have correct size/thread. You may need to cut bolt length, as I believe they are something like 5/8"(don't bet your life on that).
     
  9. bmcdaniel

    bmcdaniel Senile Member

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    It's almost always the shortest rod. Sometimes they only give you one rod and it's installed and always too long. In the past I've cut 3/8" out of the rod and welded back together. Another time I put 3/8" spacers between the MC and fire wall. Last time I bought an adjustable rod.
    https://www.performanceonline.com/Ford-Mercury-Manual-Master-Cylinder-Push-Rod-Kit/
    I did have to remove a little material off the flat part in rear, it kept my brake lights on all the time.
     
    Last edited: Jun 7, 2021
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  10. ADOR

    ADOR Member

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    I have had to put a small flat tip in to bend the little clip before to get the rod out, broke a ear off the master before it came out. They can get tough some times.
     

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