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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 at 22:39
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    I don't know, although cross-threading is plausible – sdgfsdh Jan 25 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 at 0:37
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    @gschenk yes indeed. I wasn't expecting any trouble – sdgfsdh Jan 26 at 1:10
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    @Criggie There is an o-ring on both levers – sdgfsdh Jan 26 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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