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Hayes 9 rebuilt caliper now wont bleed properly

gtd.gtd. Posts: 626
edited August 2010 in MTB workshop & tech
had a problem with the from brake on my bike wouldnt bleed fully and could hear a faint squeek from the Master Cylinder Cap assumed that was the problem so fitted a new one.

was better but still wasn't working properly so swapped the levers over and re bled

back brake was still nice and strong front was still weak

Looked at the pistons one wasn't sitting properly and was sticking

So rebuilt the caliper, now its worse than before cant seem to get it to bleed properly and brake is weaker than ever :?
Mountain: Orange Patriot FR, SubZero & Evo2LE.
Road: Tifosi Race Custom.
Do it all bike: Surly Disc Trucker 700c/29er

Posts

  • supersonicsupersonic Posts: 82,708 Lives Here
    Are the seals in properly?
  • gtd.gtd. Posts: 626
    The were before I put the pistons in, I even turned them round in there groove to make sure.

    Just got a fresh bottle of dot 4 to see if that was the problem.
    Mountain: Orange Patriot FR, SubZero & Evo2LE.
    Road: Tifosi Race Custom.
    Do it all bike: Surly Disc Trucker 700c/29er
  • supersonicsupersonic Posts: 82,708 Lives Here
    DOT can quickly take moisture in, and if any air trapped in the caliper. Try another bleed, but tap the caliper as you do it - may free some air bubbles.
  • gtd.gtd. Posts: 626
    tried again with fresh fluid... no better

    when pulling the lever when squeezing the syringe I can feel there is pressure there but when I close the bleeder and refit the cap the brakes don't work :?
    Mountain: Orange Patriot FR, SubZero & Evo2LE.
    Road: Tifosi Race Custom.
    Do it all bike: Surly Disc Trucker 700c/29er
  • supersonicsupersonic Posts: 82,708 Lives Here
    Could be a big air lock somewhere.
  • tri-sexualtri-sexual Posts: 672
    are the brakes properly bleed with no air bubles? if not try the official hayes bleed.
    makes bleeding hayes brakes a doddle.
  • gtd.gtd. Posts: 626
    tried taking the caliper off and bleeding at all sorts of different angles still no joy

    no air bubbles, its quite annoying now looks like I wont be able to use my bike till I get this sorted
    Mountain: Orange Patriot FR, SubZero & Evo2LE.
    Road: Tifosi Race Custom.
    Do it all bike: Surly Disc Trucker 700c/29er
  • gazeddygazeddy Posts: 305
    pump the lever up on the bike. it sounds like a seal is letting in air. pump the brakes up on the bike watching for fluid leaking
    I rode what you dug last summer
  • gtd.gtd. Posts: 626
    been using syringe to push fluid in - Hayes bottle to collect from overflow.
    changed back to Hayes bottle using Hayes bottle to refill and they are working better.

    The last time I tried the syringe I tried "degassing" the fluid by using a small mole grip to clamp the pipe - there were a lot of bubbles that were stuck to the syringe wall that wouldn't release. these bubbles looked as if they were trapped in the walls of the syringe. when I tried degassing the fluid the only way to describe how it looked was like champaign but no matter how hard I flicked the syringe the bubbles wouldn't rise to the top and burst they would form a "head" also a lot of bubbles wouldnt move at all either.

    As the syringe used to work better I'm wondering if the dot fluid has over time degraded the plastic body of the syringe? :| thinking about it I've also used it for LHM fluid on some Magura brakes. Even though I thoroughly cleaned the syringe when changing fluid, the two fluids may have damaged the syringe causing problems in getting a good bleed.

    Might get another two syringes keep one for DOT and one for LHM

    still one piston is a little sticky so I'm going to swap the callipers over, then re-bleed so the one that works better is on the front and the that doesn't grip as well is on the back.
    Mountain: Orange Patriot FR, SubZero & Evo2LE.
    Road: Tifosi Race Custom.
    Do it all bike: Surly Disc Trucker 700c/29er
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