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Shimano m8120 calipers leaking at bleed port

1311 Views 4 Replies 3 Participants Last post by WHALENARD, Oct 20, 2021

BikesDogsBrews

Discussion Starter · Oct 20, 2021

I recently noticed that both my front and rear m8120 calipers seem to be slowly leaking fluid from the bleed ports.
Most of it gets caught in the dust cap but its just enough to ooze out the sides. I tried tightening the bleed port nut more, but they are already pretty tight (Shimano manual says something like 6Nm, I'm probably over that now).
The reason this came up was that I had a contamination issue on my front pads but still haven't been able to find the culprit. I tried putting a bleed block in the caliper with the lever pulled over night to check for leaking around the pistons but no signs of oil. So I'm thinking it must have come from the bleed port. Calipers are about 10 months old, came stock on a 2021 Pivot Switchblade.

Is this a warranty issue or is there something I can do myself to address it?

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WHALENARD

· #2 · Oct 20, 2021

The taper on the bleed screw meets a very precise taper in the caliper. When you over tighten them you're bound to misshape one or the other. You could try new bleed screws in hopes that that's the culprit.

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chiefsilverback

· #3 · Oct 20, 2021

I had the same issue with the M6100 caliper. and I think it was due to not properly cleaning the bleed port once the bleed was done, and that small amount of oil worked its way out due to vibration and heat and contaminated the pads and rotor. I replaced both, bled the brakes again and gave the bleed port a proper clean with isopropyl alcohol and it's never happened again.

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BikesDogsBrews

Discussion Starter · #4 · Oct 20, 2021 (Edited)

I've cleaned it a couple times at this point but the oil keeps coming back, usually after a ride with heavy braking.
I didn't go crazy tightening the bleed nipples after bleeding the brakes, are they pretty easy to deform?

Edit: looks like the nipples should be easy to replace. Do the threads need to be greased with anything?

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WHALENARD

· #5 · Oct 20, 2021

BikesDogsBrews said:
are they pretty easy to deform?

Not sure though you do see one or two of these threads a year I'd say. They're also fairly common on motorcycle and dirt bike forums. It would be a shot in the dark and a guess to say how much of that's from over tightening but I am sure some of them are. I'd also wager for at least some of those that think they're cylinders are weeping it may well be the bleeder.
For the record I never break out my torque wrench to cinch them down but I am very mindful of the feel when I do. Hand tight and a scooch.

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