i recently took my bike to the LBS for brake service. Everything was fine until i noticed that the right lever (back brake) was leaking.

Every time i press the lever, it sort of "burps" a bit of oil and makes... funny sounds. (seen in picture 2)

I tried un-tightening the top cap, which really helped a lot but im not sure about the origin of the problem. I should note that when i took it to the LBS for bleeding, the pads were 80% worn. After i replaced them, the problem appeared (the mechanic said it's fine if you do that, but i doubt it). I should also note that i torture them a lot.

. .

  • I imagine the cause of the problem was overfilling. Shoving new pads in a system bled for 80% worn ones will definitely result in overfilling.
    – MaplePanda
    Nov 30, 2020 at 20:09

2 Answers 2


The first thing to check is that the rubber gasket in the brake lever reservoir is fully intact and in place. They can get both torn and clamped out of position, and that would be consistent with having just been opened up for bleeding. Make sure the reservoir is turned horizontal when open so fluid can't spill out.

If it's leaking anywhere else, there's not much that can be done other than replace the lever.

  • 2
    I cleaned it up and rotated the steel gasket with a screwdriver (picture 2) until all the dirt got untrapped. It's working fine now, just needs an oil top up. Thank you!
    – Alextsil
    Dec 26, 2017 at 13:32

You need cheking where is leaking oil. If leak master-cyclinder you most reassemble them. Very accuratelu clean in gasoline and assembke. Problem usually in small dirt between rubber gaskets and cyclinder. And remember what that sort of brakes used mineral oil. Dont DOT4 or 5 !!!!!

  • The leaking point is seen on the 2nd picture. The truth is it was really dirty before i took the picture
    – Alextsil
    Dec 25, 2017 at 21:01

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