Has anybody dismantled and successfully re-assembled a shimano hydro caliper as far as popping the pistons out and inspecting the square seals? Deore M615 I’m talking about in my case.

Done it with M785 XTs, essentially the same thing. Try to pump pistons out evenly as far as possible before splitting the caliper as it’s easier than trying to pump air into a caliper half, Bear in mind that spares aren’t available from Shimano if needed, but somebody like Sealmasters may be able to match seals for you.

Won’t O rings work?

Anyone tried?

Just wondering after “that” debacle.

seals are typically proprietary parts designed to work with the piston / caliper bore

lubricant could also be an issue? Silicon grease is used on DOT system for piston replacements but no idea what Shimano’s pistons are lubed with, and silicon could damage the seals or cause contamination to the mineral oil?

erm… you lube the seals with the fluid you use in the caliper. Either DOT fluid or Mineral fluid BUT NEVER MIX THEM 😯 😀

As for O-rings instead of the correct seal – No they are not the same thing.

PS; I design brakes for cars for a living and they’re exactly the same.

Thanks for the replies, I’ll probably try to strip it down as I don’t know if i can be bothered sending the whole brake assembly back to CRC for evaluation when I can get a new slx caliper for £21.
It just surprised me that I’ve had problems with it so early on – brake is about 10 months old but has seen hardly any use, and Shimano hydros have a reputation for reliability. You are right I can’t use o rings – it’s a square seal that deforms and pulls back into shape to retract the pistons for pad clearance. It’s really annoying that Shimano don’t make any spares available.

Has anybody dismantled and successfully re-assembled a shimano hydro caliper as far as popping the pistons out and inspecting the square seals?

I have and posted my experiences on MTBR

Not done a Shimano brake but recently done a set on Avid elixirs.
Surprisingly easy, used a track pump with a adaptor for airbeds/beachball to push the pistons out(guides online,youtube).

Stripped one caliper at a time so you always have a built one to refer too.

Thoroughly washed them down with a bit of soapy water including the seals(on elixirs 1 x O-ring and 1 x square edged piston seal, I’d imagine Shimano can’t be that much different).
left to dry on a radiator then reassembled with some silicon grease(just use mineral oil instead for the Shimano)

If there goosed then you have nothing to lose except time.

@JAG

you don’t “lubricate” seals in a DOT brake with DOT fluid – DOT is not a lubricant in any way as it causes the piston seals to slightly swell (helping to provide the seal around caliper bore).

I don’t doubt you design brakes for a living, but all of the factory training as a mechanic I received from Hope and Avid included always using silicon grease as a seal lubricant when rebuilding DOT based brakes.

In fact, Hope provide “hunter” silicon grease and Avid provide “Pit Stop” silicon grease as part of their service kits.

The amount of customers I have helped over the years who tried to rebuild their DOT brake using DOT as a “seal lube” and then wondered why the brakes still suffered sticky pistons simply proves that the factory training I received was of course correct….