'70 brake failure??? - NCRS Discussion Boards

'70 brake failure???

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  • adam schorr

    '70 brake failure???

    While out for a what turned out to be a very short pleasure cruise this evening, the brake pedal on my '70 LT1 (no power brakes) got spongy, and eventually went almost to the floor. The system was bled last month, by a mechanic I just started working with and trust. He replaced the fluid with DOT 4 brake fluid and said everyting looked fine. I have driven the car about 30 miles since bleeding.
    The master cyl has about 2/3 fluid. The front diaphram is extended. The rear diaphram is partially extended at an "uneven" angle.
    I looked behind both front wheels for leaks at the calipers, hoses, and on the tires. I also checked the rear although they are harder to see. I don't see any leaks.
    The car had a body on resto in 1989, in Californina (now in Connecticut). I have an 8/23/89 receipt from R&J Corvette Parts, Anaheim, indicating purchase of mstr cyl (part #40090), brake calipers (#40082, 83,84,85) and core. I assume these are stainless calipers...
    The stamp on the master cyl and cover are correct. The car has scored two Long Island Metro chapter top flights.
    Any ideas what could be wrong?
  • adam schorr

    #2
    Re: '70 brake failure???

    12 hours later, this morning, I drove the car...Now, the brake pedal feels normal.
    ANY adivse would be appreciated.

    Comment

    • Louis Kolb

      #3
      Re: '70 brake failure???

      Before changing parts, I would verify that there is no longer any air entrapped in the system. Since the system has had the fluid replaced, a bubble may still exist.

      Comment

      • John H.
        Beyond Control Poster
        • December 1, 1997
        • 16513

        #4
        Re: '70 brake failure???

        If it came "back to normal" sitting overnight, I doubt if it's air in the system; if you lost that much pedal initially, I'd suspect the master cylinder.

        Comment

        • adam schorr

          #5
          Re: '70 brake failure???

          Hi John,
          If it's the master cylinder, would you advise a re-build, or finding a correct replacement? I checked the stamp on the engine side: #5455509, which matched the judging manual. The cover has the correct stamp and is gold irridite. Should I be concerned with keeping this exact unint, or would any correct (semi-flat black, etc...) master cylinder be okay? Who sells correct replacements (if recommended)?
          thanks!

          Comment

          • Jim T.
            Expired
            • March 1, 1993
            • 5351

            #6
            Re: '70 brake failure???

            If it was mine I would buy a rebuild kit and install it. Not all to difficult, make sure you bench bleed. Rebuild kit may come with plastic fittings and hoses to help bench bleed. Keep it clean, no contamination during rebuild.

            Comment

            • Gary S.
              Extremely Frequent Poster
              • July 31, 1992
              • 1628

              #7
              Re: '70 brake failure???

              Master cylinder, rebuild it if the bore is perfect and unscratched. Easy one hour job.
              Gary

              Comment

              • adam schorr

                #8
                Re: '70 brake failure???

                Thanks Gentelmen!

                Comment

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