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Brake pipe union. What size?

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  • Brake pipe union. What size?

    Can anyone plese tell me what size is the brake pipe union for the front calipers and rear wheel cylinders for a 1980 Marina 1700? I have got as far as removing the front calipers and partial disassembly of the rear brakes. I cant shift the union between the brake pipe and the caliper body, or the pipe and the wheel cylinder at the rear (admittedly I am using an open ended spanner not the specialist tool). I can feel it rounding. I managed to successfully free the bleed valves with the WD40 and hammer tap method. The unions have defeated me. I have compromised at the front end and removed the brake pipe at the end of the flexible hose. So I have two dirty old calipers with curly pieces of copper pipe attached. I cant remove the unions to show to someone behind a counter for a replacement. I have got some remanufactured calipers and new wheel cylinders so new parts is essential.
    Ebay is awash with packets of male and female UNF and Metric unions and I am keen to flare some copper pipes and get on and fit my new calipers and wheel cylinders. I am ready for any advice please.

  • #2
    Re: Brake pipe union. What size?

    Paul,
    The size you require is 3/8ths unf for the front and rear[into caliper and into cylinder]I have just rebuilt the calipers on my son's roadster and had the same problem as yourselfand resorted to mole grips to undo the pipe union.The calipers required a thorough clean and new seals[?12]but now work perfectly

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    • #3
      Re: Brake pipe union. What size?

      Alan, Thanks for your advice. Glad to hear that your sons' Roadster is up and running. I took a new wheel cylinder to Partco in Sheffield, which is rapidly becoming my favourite shop, and asked them for the male unions that would fit. The man found a pot of powertrain male unions tried one and it fitted. He admitted that he didn't know what size it was. He was pretty sure it wasn't metric so I passed on your information regarding the fact that they would be 3/8ths UNF. He gave me a dozen for free!

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      • #4
        Re: Brake pipe union. What size?

        Message originally posted by: jim mountain
        To get the old pipes out, first I would always soak them in WD40 for a few hours (over night if poss.) first.

        Then you will want the use of a brake pipe spanner, (a ring spanner with a small bit cut out to fit over the pipe, normaly deeper and with thicker walls than a normal ring spanner).

        These can be quite cheap but beware !, you get what you pay for, I have used cheepie ones in the past, and nearly been brought to tears, if you can get hold of a Snap-On one do, (try ebay, you can't beat Snap-On even if they are a bit pricey), this will save you time and effort in the long run.

        Once you have you brake pipe spanner on, (now bear with me), give the spanner a knock (1/8 th of a turn) in the wrong direction, as if you where doing it up, this tends to free off the nut, then you should be able to get it undone now.

        best of luck to you

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