Master cylinder bleed nipple threads wet

Discussion in 'Tech' started by svracer22, Jul 2, 2019.

  1. svracer22

    svracer22 Well-Known Member

    This is the stock front master cylinder for a Daytona 675. I recently bled the brakes and now I'm noticing brake fluid at the base of the bleed nipple threads. The brakes are solid so I'm not sure whats causing this.
    Should I simply replace the bleed nipple or is there a problem with the master cylinder?
     
  2. RM Racing

    RM Racing Tool user

    Spray some water on the area, then blow it dry thoroughly with compressed air. It’s likely you have residual fluid from the bleed. If the fluid returns, then you need to take action.
     
    Shenanigans likes this.
  3. gapman789

    gapman789 Well-Known Member

    Clean /dry the rubber bleeder nipple cover too. Its likely to have residual fluid in it.
     
  4. IrocRob

    IrocRob Well-Known Member

    Typically when brakes are bled fluid still sits in the bleed nipple. When you press the rubber cap over the nipple it can create enough
    pressure to push that little bit of fluid out around the threads. As said above, compressed air works quickly, but I just don't like to blow
    little bits of brake fluid all over.

    I use the "stick" of a "Q-tip" to remove that bit of fluid from the nipple. Cut the cotton end off the q-tip and the stick fits quite well
    into the nipple, pushing the remaining fluid out and onto a paper towel. A bit more tedious this way but it works for me.
     
    Newyork likes this.
  5. RM Racing

    RM Racing Tool user

    Hence the water. Dilutes the hygroscopic brake fluid.
     
  6. Britt

    Britt MotoBigots Suck

    I twist up the corner of a paper towel and insert it into the nipple hole..it absorbs the fluid, remove the paper towel, put the cap on.
     
  7. svracer22

    svracer22 Well-Known Member

    Its definitely not coming from the center of the nipple. I use a paper towel rolled up corner to get all the fluid out and the cap is clean.
    I also cleaned the fluid from around the threads, the next day the fluid had returned. I will try what Rick suggested and see what happens.
     
  8. RM Racing

    RM Racing Tool user

    I've seen your paper towel twist and it needs work. ;) Not really.

    Happy Fourth 'Merica!
     
    Britt likes this.
  9. beechkingd

    beechkingd Well-Known Member

    There might be some debris on the seat that is letting fluid past. Loosen and retighten the nipple while holding pressure on the lever.
     
  10. beathiswon

    beathiswon Well-Known Member

    No way to know without taking it apart and inspecting both pieces. Any sign of galling is bad. In case you don't know already bleed screws don't need to be tightened with a lot of torque which can deform the sealing surfaces.
     
  11. Spitz

    Spitz Well-Known Member


    Right, but there is no sealing done between the nipple and the threads, it can weep out if there is fluid in the nipple.
     
  12. blue03R6

    blue03R6 Well-Known Member

    you never said if you tried to tighten the bleeder more. you could use thread sealant if you can't buy the bleeder. just use automotive grade thread sealer. not something from home depot in the plumbing isle.
     
  13. Britt

    Britt MotoBigots Suck

    Bleeders do not seal on the threads...they seal on the taper and seat.
    Thread sealer is a bad idea.
     
    KneeDragger_c69 likes this.
  14. dudutzu

    dudutzu Well-Known Member

    OP, please don't do that ^^^! That's NOT pipe thread, therefore no sealant is necessary. Don't use any thread sealant, it's not going to do any good, other than making a mess of your M/C.
    All the sealing is happening at the tip of the bleeder screw, if it's not sealing - then the problem is there.

    EDIT: Britt beat me to it
     
    Britt likes this.
  15. RM Racing

    RM Racing Tool user

    Britt=smart.
     
  16. blue03R6

    blue03R6 Well-Known Member

    just do it don't be a bitch. safety. lol
    also atf in your forks is the same as fork oil.


    joking aside, when you buy a new one, it has thread sealant on it.
    i'm going to have to do a lot of teaching you guys on this forum I see.

    [​IMG]
     
    Last edited: Jul 5, 2019
  17. Britt

    Britt MotoBigots Suck

    Do you know what that "Sealant" is for?? Not Joking.

    Depends on the viscosity of the ATF...
     
  18. blue03R6

    blue03R6 Well-Known Member

    look above. new ones come with thread sealant.
     
  19. Britt

    Britt MotoBigots Suck

    Well then I suppose you "know" it is for keeping air from leaking past the threads when you are using a vacuum bleeder...NOT for sealing the fluid in the calipers.

    Or maybe you can learn me sumpthin.
     
  20. blue03R6

    blue03R6 Well-Known Member

    no, that's not why it's there.
     

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