Quick question… last time I bled my XT brakes I noticed that the oil was getting pretty dark, so I figure it’s time to fully flush it out (especially as performance is all over the place currently).

What’s the best way to do it, gravity from the top and leave it a while, or force it from the caliper using a syringe?

You’re supposed to do it from the bottom up using a syringe, according to Shimano. That’s certainly how I’ve always done it.

“dark” oil has usually been indicative of seal degradation in my experience.
Probably easiest flushed bottom-to-top but it may only provide brief respite from the “all over the place” performance. If they’re still under warranty (2 years) I’d be tempted to warranty them.

Sadly they’re older than that, and to be honest they’ve been pretty shitty from day one, so I wouldn’t be surprised if there was something wrong with the seals.

Thanks for the info.

bottom-top then top-bottom http://www.epicbleedsolutions.com/blog/how-to-bleed-new-shimano-brakes/

ime steps 12 & 13 need repeating *many* times

^ this. I really don’t understand why everyone thinks a good bleed on Shimano is any easier to get or more likely to stay around than with Avid/SRAM. IME, if anything Avid/SRAM is actually less hassle to bleed well so long as you don’t try to pretend you’re doing Shimano or have ancient syringes with knackered seals.

I followed the epic instructions to flush some Deores and they have been fine since. The fluid was more grey than red which I think happens with the heating up and cooling down of the fluid over time.

As above – heat rather than seal degradation is the reason for blackened fluid IME.

Not saying that seal degradation is never the cause, but it’s certainly not the most common. I’ve bled brakes at DH races that look like they have squid ink in them. If this was due to seal degradation, there’d be no oil left in the system, as there would be no seals left!

Couldn’t actually add oil in at all. Master cylinder problem. Have currently got it all stripped but I think in reality I’m probably going to need a new lever…

…and because you can’t seem to get them at the moment I’ll probably be getting the M8000 instead.

I’ve bled brakes at DH races that look like they have squid ink in them.

Well look at that link:

fixing XT M785

I did what he said last week end and it fixed it! And I’m not a great mechanic – Putting all back together was fiddly – and don’t break the small spring in the lever.

Cheers. Will have a look.

Took far more sanding than I expected, but that did the job. Thanks.

Hopefully it’ll hold up.