Bleeding shimano brakes! What am I doing wrong?

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  • Bleeding shimano brakes! What am I doing wrong?
  • Premier Icon ir_bandito
    Subscriber

    Just spent the best part of 3 hours trying to get a new (old) XT brake working. The hose wasn;t connected to the lever when I got it, and the system was drained. So:
    Fitted hose to the lever, with connecting bolt, olive and insert all in the right order.
    Followed shimano instructions to fill and bleed the system until no more visible bubbles.
    And nothing.
    Lever moves all the way back to the bars with the caliper bleed nipple closed and reservoir full and sealed shut. Absolutely no resistance and no visible piston movement. Which implies there's a whopping great air bubble in there somewhere, but I completely flushed it through, and there're no visible leaks.
    Any suggestions what I've done wrong would be greatly appreciated as I'm going to miss tomorrow night's ride now 🙁

    Premier Icon mboy
    Subscriber

    Reverse Bleed it

    Buy yourself a syringe and a short length of tubing, fill with oil, attach to the bleed nipple on the caliper and bleed it that way…

    Works WAY better than normal bleeding on Shimano brakes.

    Premier Icon ir_bandito
    Subscriber

    Cheers. I'll give that a go tomorrow night then.

    deserter
    Member

    did you back bleed it or fill the resevoir and pump until no air?

    I prefer to back bleed personally which means you pump the fluid back from the caliper, give you hoses a flick and try again

    zaskar
    Member

    I've done it the shimano way-instructions from their tech site no problemo but people seem to be always stuck.

    But syringe method can work well too.

    Premier Icon Northwind
    Subscriber

    Reverse bleeding from the caliper is the best option IMO, works just as well on motorbikes. Air wants to go up after all. And the hardware needed costs buttons, compared with hilariously expensive bleed kits.

    bunnerscj
    Member

    yup, just done mine tonight, back bleed from caliper, gently squeeze fluid through, tap hoses every so often and jobs a good one !

    Premier Icon ahwiles
    Subscriber

    for the brake perverts out there, here are 2 tricks of mine:

    1) remove the nipple, and wrap the thread in ptfe tape – a few turns will do, this stops any air/oil leakage around the thread during bleeding.

    2) put your mineral oil in the freezer over night before use, this will cause a lot of air to come out of solution.

    oh, and yes, a syringe is the way to do it – i get mine from boots, the little 5ml ones for feeding/dosing medicine to babies.

    is it just me? or is it practically impossible to buy syringes? – i get all sorts of funny looks when i ask for them, maybe i look like a smackhead…

    luked2
    Member

    is it just me? or is it practically impossible to buy syringes? – i get all sorts of funny looks when i ask for them, maybe i look like a smackhead…

    Not just you. At the chemist in the village they looked at me like I was muck. They were fine when I bought a toothbrush.

    tang
    Member

    i got dosing syringes from the vets, they gave me a few for nothing. also after reverse fill, and tapping session leave the levers pulled in with an elastic band overnight, in the morning there might be a few bubbles to deal with.

    carlphillips
    Member

    assuming you have done everything correctly, and it still doesnt work then you may have to consder that you have a leakl somewhere, have you checked the hoses for any signs of damage, there could be a leaky piston seal or otherwise somewhere..?

    my glass is always half empty btw…!

    Rich_s
    Member

    Having failed to track down syringes from the usual suspects (Boots etc) I wandered randomly into a small chemists on the high street in Middlewich, wandered up to the counter and asked for a 10-25ml ish syringe. Girl behind the counter asked "Oh, is it for a mountain bike?".

    At that moment I knew I had a bad habit and sharing needles is BAD 8)

    I pretty much put up the same post about three months ago, reverse bleed is the way to go.

    "Why wont my brakes work?"

    If you're very lucky a nice person from the forum who lives locally will pop round and show you how to do it in return for ale.

    Thanks again Sobriety, I owe you one 😉

    ziwi
    Member

    If you can't get a syringe, push the levers a few times until the pistons come quite far out, then push the pistons back into with a screwdriver – you will suddenly see loads of bubbles popping out the reservoir, repeat as necessary. I asked the same question, got that advice and it solved the problem in 10 minutes.

    Premier Icon Northwind
    Subscriber

    "is it just me? or is it practically impossible to buy syringes? – i get all sorts of funny looks when i ask for them, maybe i look like a smackhead… "

    That's a LOT of smack!

    Premier Icon mboy
    Subscriber

    "is it just me? or is it practically impossible to buy syringes? – i get all sorts of funny looks when i ask for them, maybe i look like a smackhead… "

    LOL

    That was the justification I tried to use in boots last time… Still looked at me funny! Maybe they thought i really was gonna inject 25cc+ of scag into my veins in one go, instantly killing myself!

    Best bet funnily enough is your local cartridge world… Guess what they use a lot of the time for refilling inkjet printer cartridges! And they've usually got a few spare in stock they'll be happy to sell you for a couple of quid…

    Premier Icon ir_bandito
    Subscriber

    Got it!
    A mate bought a load of syringes from an ebay shop for this very purpose a while ago and gave me one. Worked a treat, took all of 10 minutes and most of that was getting the bike-stand out.

    Cheers!!!

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