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My bike's Dura-Ace R9120 rear-brake/front derailleur shifter (left shifter in UK) leaks brake fluid when I pull hard on the lever. It leaks from this specific place:

Location of leak

Gif demonstrating the lever leaking

I understand this lever is mechanically identical to Ultegra R8020, and have found a couple of forum posts on other sites covering people's fixes, but these levers either leak from a different location, or the fix doesn't work e.g.

I have replaced the diaphragm and re-bled the brakes (this part: https://www.sjscycles.co.uk/gear-spares/shimano-duraace-str9120-lid-unit-left-y0c598030/). The lever is firm and works well, but if I pull hard on the lever it leaks.

Is this lever repairable?

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    just wondered if you ever fixed this issue, as exactly the same thing has happened to mine! Commented Nov 6, 2022 at 16:53
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    Sadly not. I think it's a known issue that would result in a new lever if you still have warranty. I ended up buying a used one that so far seems OK - not cheap, obviously!
    – Paul Suart
    Commented Nov 6, 2022 at 20:33
  • I wonder if there's a recall for this model of lever, have you tried looking on Shimano's site/Google, or spoken to your local bike shop (ideally one which is an Authorised Shimano Service center??) hope that helps Dan
    – Munkeh72
    Commented Jan 19, 2023 at 11:51

1 Answer 1

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Basic hydraulic systems in terms of actuation or movement, from bottom to top, involve:

  1. Caliper pistons - push the pads against the rotor
  2. Brake fluid - transmits lever movement to the pistons
  3. Master cylinder - a syringe-like part actuated by the lever blade to push brake fluid to the caliper
  4. Reservoir - supplies the master cylinder with fluid when it's not actuated in order to compensate for the extra travel caused by pad wear.

I don't know if there was a batch recall problem with those brifters, but if squeezing the lever (which should close the port between the master cylinder and reservoir) causes backflow to the reservoir, then your MC valves/seals are likely damaged or defective. You might need new brifters.

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