Master Cylinder Question

Discussion in 'Troubleshooting & Diagnosis' started by mallard, Jul 9, 2019.

  1. mallard

    mallard Veteran Member

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    My 74 Z needs a master cylinder. Although everything works fine (no fade or spongy pedal yet) it's developed that patented leak between the cylinder and the booster. It's been nearly 40 years since I've gotten a replacement cylinder for anything so my question is what are the experiences with replacements? The picture of what Amazon sells looks much like factory original. While I like the idea of the stock look, it's hardly a deal breaker.

    I have a good used MC from a 74 that I dismantled nearly 30 years ago but I'm reluctant to go that route for something that critically important.

    What are the experiences?
     
  2. Gary S

    Gary S Administrator Lifetime Gold Member

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    If you look hard enough, you might be able to find rebuilt original ones yet, but rebuilds are a bit risky unless you know for sure that they were bored and sleeved. Usually after that many years they fail due to corrosion in the bore. Any left over pitting in the bore can make them less reliable after the rebuild. You can also find new ones made later. They will be a bit different in appearance. Usually the new ones don't have the bleeders that the old originals had, but you don't need them.
     
  3. shanghai Kid

    shanghai Kid Member

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  4. TommyRS70

    TommyRS70 Veteran Member

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    Steve Gregori, brakebooster.com is a stand-up guy. Replated and rebuilt my original booster. Also clear zinc plated a number of other parts. Nice work!
     
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  5. mallard

    mallard Veteran Member

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    Hopefully I won’t need a booster just the mc. Just curious if posters have had good luck with amazon or other similar quality MCs.
     
  6. Gary S

    Gary S Administrator Lifetime Gold Member

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    Every time I've replaced a master cylinder, I got mine from my local auto parts stores. I've had great luck with them....no failures, but buying local gives me a place to go if there was ever a problem.
     
  7. 2hipZ/28

    2hipZ/28 Member

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    Ugh , I wish I could say the same about having good luck . I went through 2 brand new MC form O'Reilly's that leaked but the 3rd MC from NAPA was a charm. I bench bleed all 3 being very careful not to push in more than 1" and getting all the air bubbles out. The first 2 leaked at the rear seal after I installed them.
    I gravity bleed all 4 wheels keeping an eye on the reservoirs so they stayed filled with brake fluid. The rear drums were fine but I had to use the vacuum pump on the front discs.
    I agree with Gary about buying local, O'Reilly's refunded my money.
     

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