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Bleeding Front Brake Help (moved from DYI)

Discussion in 'XJ Technical Chat' started by k-moe, Mar 18, 2017.

  1. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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  2. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    I have a few questions for you yo help diagnose the problem.

    1. Which XJ do you have? There are various brake systems, and they all have slightly different needs when it comes to bleeding them.

    2. Did you also rebuild the calipers, and fit new brake lines?

    3. If the brake lines were off, did you use new crush washers, or a least anneal the old washers?

    4. When you rebuilt the master cylinder, where did you get the rebuild kit from, and were you certain to fit the new piston seals in the correct orientation?

    5. Are you positive that the return port on the master cylinder is clean and passing fluid?
     
  3. dowski68

    dowski68 Well-Known Member

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    I seem to be having the same problem.
    I just rebuilt the front calipers- new rubbers/ new pads / rebuild kit for master cylinder on the way.
    Have ran 3/4 of a large bottle of Brake fluid through the master cylinder and I still have to pump the handle three our four times before I get solid resistance.
    86 Yamaha XJ700X
    Yes I have or believe that I have got all the air out- apparently not or maybe the 2nd hole in the master cylinder is clogged ?
    Not sure just trying not to get overly upset.
     
  4. dowski68

    dowski68 Well-Known Member

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    people are like well it should be cool when your riding and my response is yeah it is like opening your oven and sticking your face in there. especially when it is 90+ degrees
    the price I pay for riding. Still worth it though
     
  5. HalfCentury

    HalfCentury Member

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    Compared to carbs, brakes are simple. If the brake is spongy, you have a problem. Replace all of the soft parts in the caliper and the master cylinder. Use a Mighty Vac to pull the air from the bleeder nipple.

    The master cylinder bore and the caliper bore and the caliper seal channel all have to be honed to be smooth. This takes some time and patience.

    You can have a leak anywhere in the system. That will prevent pressure. You have to check everything in the brake system.
     
  6. tabaka45

    tabaka45 Well-Known Member

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    When I completely rebuilt my 85 XJ700N brakes--master cyl, calipers, brake lines-- I was able to bleed my brakes in about 15-20 minutes. I reverse bled them, i.e. from the bottom up. My theory is that it is easier to push air up than to push fluid down. Go to Tractor Supply, or similar, and buy a large plastic syringe and about a foot of clear tubing to fit over the syringe tip and bleeder valve. Fill the syringe with brake fluid, attach the tubing to the syringe, push brake fluid into the tubing, attach the tubing to the bleeder valve and use the syringe to push fluid into the caliper slowly to allow the fluid to fill the caliper and brake line while pushing the air out through the master cyl. If the syringe is completely filled it may be enough bleed one side. If not, close the bleeder valve and refill the syringe and reattach the tube to the bleeder valve. If there is any air in the tubing hold the syringe above the bleeder valve and let air bubble float up and into the syringe, then with a completely filled tubing open the bleeder valve and continue pushing fluid into the cylinder. Stop when fluid reaches the master cyl. Repeat the process on the other side but go slow since there is already fluid in the upper line and master cyl. Like I said, it took me about 15-20 minutes. If you can't find a syringe locally, get one on EBay.
     
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  7. dowski68

    dowski68 Well-Known Member

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    Well that makes sense, I know what I am doing tomorrow morning.
    Thanks for the tip I will let you know how it works
     
  8. tabaka45

    tabaka45 Well-Known Member

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    Go slow. If you "squirt" the fluid you run the risk of introducing small bubbles inside the caliper.
     
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  9. cgutz

    cgutz Well-Known Member

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    I went a little too fast with this method and shot a stream of brake fluid up through the open master cylinder and across the driveway.

    It worked though.
     
  10. tabaka45

    tabaka45 Well-Known Member

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    Congratulations! Good thing no one was "keeping an eye" on the master cylinder!
     
  11. dowski68

    dowski68 Well-Known Member

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    Today turned out to be relocating fire wood day.
    Although I did buy a syringe, tubing and more brake fluid.
    Also went for an evening ride as it got to 103 degrees today.
     

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