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Mucky brake fluid...

williambowlandwilliambowland Posts: 131
edited October 2010 in MTB workshop & tech
I have some well used Juicy 3s on my ride - they need regular TLC to keep them working nicely.

I bled the the rear brake last night - there wasn't much air in the system but the old fluid was very cloudy... some black residue in there. The last bleed was only 3 months ago so I was a bit surprised that the fluid was so mucky.

Firstly... what is the residue?

Secondly... is it a symptom of some other problem - like a leak somewhere in the system or something?
2014 Giant Anthem 27.5 1
2014 Specialized Roubaix SL4 Disc


  • louselouse Posts: 80
    black stuff is rubber. and it could have been there for ages as it does not always come out.

    if the brake feel fine then dont worry.

    they should not need bleeding that much so i would say you have wornout seals.
  • peter413peter413 Posts: 5,120
    Fluid is perishable and doesn't have a set lifespan so I wouldn't say that your seals are definitely worn out, it might just be that you using up the life of the fluid quicker than many others.

    Just like with brake pads, just because someone can make them last 2 years, doesn't mean you will
  • Thanks gents...

    The brakes didn't need to be bled as such, they felt fine... I just thought I'd do it whilst I was replacing the pads. As I say, there wasn't much air in the system, only the residue.

    I did a couple of bleeds about 3 months ago - I had never done it before and the system had seen about 18 months of use. I got a fair bit of residue first bleed - the second bleed was clean. Based on that - I was surprised to see so much residue this time after the clean bleed 3 months back.

    The seals you refer to - they are at the caliper / piston interface, right? I guess there are some in the master cylinder too... but the caliper ones are more likely to be the culprit?
    2014 Giant Anthem 27.5 1
    2014 Specialized Roubaix SL4 Disc
  • konadawgkonadawg Posts: 447
    Why bother, if they work they work, fix when broke.
    Giant Reign X1
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