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Air in brakes

Discussion in 'Technical and Troubleshooting Torque' started by nicka, Mar 21, 2007.

  1. Sorry but it has more than likely been covered here before but i have bled my brakes a few times with no problems at all but this time there is constant air in my GSX1100 rear brake when i try to blead it.
    I was thinking a lead in the line but if this was the case wouldn't it leak out when it was under pressure??

    Or would it be the master cylinder seal that leads the air in on return of the foot lever and if so can these seals be replaced or do i need to replace the whole cylinder.


  2. The topic HAS been covered a lot, but that's because it's kinda important. Common wisdom seems to be that modern bike brakes need a lot of bleeding, and sometimes just tilting the bike over a bit makes a difference in shifting the recalcitrant little air bubbles.
  3. Are you sure the bleed nipple is shutting off. Just the slightest opening will allow enough air in. You wouldnt always see oil leaking out unless you really pressurised the system.

    The master cylinder could be sus tho as suggested. Most break joints would be able to kit it or you could have yours rehoned and sealed.
  4. Some things that i have found helpful when bleeding the brakes.

    Maybe try back bleeding.
    Also rasing the caliper can work wonder, leave it overnight.
    Shake the brake lines. Hit them with a mallet. Lightly. Especially at the joints.
    tie the lever down overnight, this helps to force air out of system.
  5. silly question too...

    When you put hte new fluid in, did you take the little rubber boot out (if it had one) before]/b] you topped it up? ;)

    your brake pads and rotors are too worn?
  6. Lets pretend you have not done this before.
    Are you:
    1. cracking the nipple
    2. firm single push of the lever
    3. closing the nipple
    4. release lever
    5. repeat, repeat, repeat.............

    I have seen people pump the leaver several times with the system open.

    If this is telling you how to suck eggs, ignore it.

  7. what the f$%k is back bleeding? im sure you made that up. ive been a mechanic over 10years and i aint heard of it, and if the brake nipple was open enough to let air in the fluid wuold aslo be coming out when the brakes are applied.

    let a qualified person do it. dont mess around with brakes
  8. I'm guessing this involves using a syringe, or similar, to inject brake fluid into the system from the calipers. I've read elsewhere that this is very effective, caus ethe air naturally wants to rise to the top of the system. Is that right?
  9. Thanks guys, plenty of replies here.

    There seems to be too much air for it just be be the air thats in the line.

    Good point but its happening with both nipples.

    Like i said above thats the air just keeps building up.

    The questions are the ones that never get answered and yes my pads are worn and need replacing :oops:
    I think i know the boot your talking about,the one under the reseve bottle lid and if so yes.

    Yep thats the procedure i'm following which is the same as i have done many times and the front brakes were not a problem.

    let a qualified person do it. dont mess around with brakes

    I do agree with you as they are important but as mentioned i have done it before without a problem.

    Thanks all for the tips and i think i'll have to pull the master cylinder apart first and if not then the pistons and if no luck i will take it in to get checked out.

    Thanks all

  10. bubbles in the brakes... I have a huge 250ml hyperdermic left over for this exact purpose to either suck the fluid through. Or in some rare case force the fluid back up the line into a near empty reserve...

    If you hit upa medical supply store they should cost aregh... $15 or so and are invaluable. Over fill your oil suck some out through the oil filler etc...

    edit: dont mix your fluids... :shock: brake fluid in the engine...
  11. You have to do this on some guzzi's with the linked brakes.

    On guzzis' like mine it's enough to raise the rear caliper.

    A big syrynge (think a horse syringe) with a bit of tubing will do the trick.

    Only to be used where really necessary... it's rather messy :)
  12. I just took the master cylinder of and it all seems O.K.

    It holds both suction and pressure so next is the pistons but as i mentioned earlier that my thoughts of it having an air leak on the pressure side would also cause it to leak fluid :?
    Anyway i let you know the outcome if i get to the bottom of it and if i don't, move over if you see me coming. :grin:
  13. Well i have fixed them but know know how really.
    I replaced the wire clamp on the hose between the reserve box and the master cyclinder as i had to cut the clamp off and i had pumped all the fluid out when i took the master cylinder off and now they bled fine.
    I would have originally bled more fluid through it than it can hold so the old fluid shouldn't have been a problem and the clamp was fine before but least i have brakes again.


    Now its decision time.

    Just got back from the bike shop and priced some parts,chain and sprockets,new brake pads and discs,engine gasket kit and dogs and gear forks as this all needs doing very very soon and i need to way up my options of spending this on this old machine or not.

    The bikes pretty clean but is it worth spending the thousand dollars or so on when after these are fixed i am sure there will be more to spend.

    Here's a latest pic of it taken yesterday at the Grampians.

    81 GSX 1100

    Anyone want to buy it :grin: but no roadworthy.
  15. Back bleedinf can be done, by taking the caliper off the bike, and pushing the pistons back into the calliper, if forces the fuid back up the line, then press the lever to make the pistons come out, and do it again.
    Found this worked after spending a few days bleeding the brakes.
  16. If you like the bike, why not spend money on it and keep it? If you're having thoughts of going to a different bike, then I don't think you should spend the money on it if you can't recover the cost through a sale.