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I noticed that a small amount of mineral oil had leaked from the bleed port on my Shimano road shifter. I inspected the bleed port screw and saw that it was loose. The threads on the lever appeared to be damaged. The threads on the bolt (Y0C698030) appear to be fine.

I was able to screw the bolt back in, pumped the lever a few times and it seemed to stay put. No further mineral oil leaked and the braking does not feel spongy.

However, now I'm not sure what to do:

  • Is the brake safe to use?
  • Can I repair the thread, perhaps with a helicoil or threaded insert? If so, what are the dimensions?
  • Do I need to replace the entire shifter?
  • Should I make a warranty claim with Shimano?

Here is the shifter diagram for clarity:

enter image description here

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    Any idea how the threads got damaged? Was the bolt cross threaded in the past? – Argenti Apparatus Jan 25 '20 at 22:39
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    I don't know, although cross-threading is plausible – sdgfsdh Jan 25 '20 at 22:58
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    The diagramm shows the brand new GRX levers. Is that what you have? In that case it cannot be older than a few months. – gschenk Jan 26 '20 at 0:37
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    @gschenk yes indeed. I wasn't expecting any trouble – sdgfsdh Jan 26 '20 at 1:10
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    @Criggie There is an o-ring on both levers – sdgfsdh Jan 26 '20 at 2:13
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I would re-tighten the bleed port screw and watch for leaks. If you get no leakage and the screw does not loosen then you are fine.

A partially damaged thread should not be a problem as the bleed port screw does not have any load on it. (There should not even be any fluid pressure on it during braking as the reservoir is cut off from the line by the piston when the lever is pulled.)

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I had exactly the same problem in Shimano 105 road shifter. I solve it by wrapping bleed screw with PTFE pipe tape and it did tightened to damaged threads in bleeding port.

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    Welcome to bicycles.stackexchange.com! It's always great to hear first-hand reports of solutions to problems. – rclocher3 Aug 6 '20 at 20:58
  • Although PTFE / Teflon tape will help and aid in sealing threads, brake fluid over time will dissolve the tape, so although everything seems good at the mo you may need to revisit the threads at a later stage – Dan K Aug 8 '20 at 8:28
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I have the same problem with Shimano GRX leaver - just found that mineral oil leaked (a spot of leaking oil is visible). bleed screw can not be screwed in (it simply scrolls in the thread). The thread exists in the port by the way. shimano Bleed Screw & O-Ring thread problem

Bleed screw

there is a thread inside the port

Thinking now how to fix such problem. For now I have next solutions on my mind:

  1. add mineral oil in the oil tank, put the bleed screw in the thread and use PTFE pipe tape to fix it as answered above - dont know how effectively this way should be
  2. bore the hole of the bleed screw port on the leaver and use a bolt with o-ring with bigger size -- also dont know if that a good way
  3. change the leaver

A bit disappoint because of getting new bike with such small but possibly costly bug of the leaver. I will update the answer with my final solution later.

  • It is frustrating how Shimano used such weak threads for this critical (and expensive) component. Many people are having this issue. – sdgfsdh Sep 22 '20 at 15:35
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    Hi, welcome to bicycles! I agree the problem is frustrating, but I'm afraid that "I'm having this problem too" doesn't really answer the question. Please only post answers that answer the question; you should read How to Answer and take the tour to learn more about how the site works. – DavidW Sep 22 '20 at 16:21
  • yep. thank u. updated the answer with possible solutions on my mind. also I'll update my final decision on that problem a bit later (when i fix it). – Alex Sep 23 '20 at 6:02
  • Shimano honors their warranty. If it's a new bike you bought, just go that route. Don't go trying to hack the lever to make it work. – Nathan Knutson Sep 25 '20 at 7:22

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