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Thread: Dead brake

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    Default Dead brake


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    Hi, my rear brake is knackered! I've done all of the usual things, bled, cleaned etc. It works for a few minutes, then dies again completely. Any ideas please?
    Ian

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    Should Get Out More Kebab The Cat's Avatar
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    Default Re: Dead brake

    Failed master cylinder perhaps?
    When you say 'dies again' what are the symptoms? Does the pedal:
    go hard, no brakes.
    go hard, locked wheel
    go soft, no brakes..

    or what?

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    Default Re: Dead brake

    Quote Originally Posted by Kebab The Cat View Post
    Failed master cylinder perhaps?
    When you say 'dies again' what are the symptoms? Does the pedal:
    go hard, no brakes.
    go hard, locked wheel
    go soft, no brakes..

    or what?
    Hi, pedal travels to a hard stop. Brake is not ceased, wheel turns freely. I pulled the piston out, refilled the system with fluid, which worked, sadly only for a few minutes.
    Ian

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    Default Re: Dead brake

    Did liquid leak out somewhere? If not is sounds like a failed master cylinder (seal) to me.

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    Default Re: Dead brake

    Quote Originally Posted by Ian07120 View Post
    Hi, pedal travels to a hard stop. Brake is not ceased, wheel turns freely. I pulled the piston out, refilled the system with fluid, which worked, sadly only for a few minutes.
    Ian

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    Default Re: Dead brake

    I'm with the cat on this

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    Default Re: Dead brake

    Quote Originally Posted by Julian_Boolean View Post
    I'm with the cat on this
    What he said.

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    Default Re: Dead brake

    Thanks for the reply. I'll give it a good clean and start again. Incidentally it's a Gas Gas 250 Cami 2014, I can't get brake parts (other than pads) I'm looking for a new caliper. I have replaced the master cylinder, a ebay cheap one which fitted! Thanks for the reply.
    Ian

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    Default Re: Dead brake

    Did it work before fitting the Ebay rear master cyclinder?

    The original brake master cyclinder wasn't made by Gas Gas, it's probably Grimeca or Brembo, should be cast into it somewhere.

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    Default Re: Dead brake

    You replaced the rear m/c? Why? Is that before or after you had problems? (It's not clear).

    I'd suggest getting old of an original OE m/c, or renewing the seal&piston in the old one.

    Looks like it's a Braketec part. http://braktec.com/braktec-is-supply...as-cami-250cc/

    You could try contacting them directly, some companies are happy to deal with the general public - at the very least they should be able to direct you to a dealer.

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    Default Re: Dead brake

    Thanks for the advice. I changed the master cylinder because I thought that was the problem. I'll check for leaks first although I haven't seen any sign of one. I'll also check the make of the caliper.
    Thanks again for all of the help and advice.
    Ian

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    Default Re: Dead brake

    Quote Originally Posted by Ian07120 View Post
    Thanks for the advice. I changed the master cylinder because I thought that was the problem. I'll check for leaks first although I haven't seen any sign of one. I'll also check the make of the caliper.
    Thanks again for all of the help and advice.
    Ian

    If the m/c internal seal is the issue (and it sounds like it is), then you won't see any visible leaks - it's the internal high pressure side leaking into the internal low-pressure side that's the issue.

    not sure how you'd visibly test it tbh..

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    Default Re: Dead brake

    If you've had the same issue with two different master cylinders then my next guess would be that the seals aren't sliding over the pot properly, so every time you relese the brake lever, the cylinder gets dragged back into the caliper. This can lead to a lot of travel on the lever.

    If that sounds likely, check the caliper seals, and check the rusty cruddy gunge in the slot that the seals sit in. Corrosion there can lead to the seals being too tight on the pot.

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    Default Re: Dead brake

    Thanks.

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    Default Re: Dead brake

    Two M/C with same issue? Did you use new copper washers on all the banjo bolts/joints.

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