Whilst riding, my front XT disk brake lever started gradually pulling all the way to the handle bar. This happened first whilst easing my self down a steep descent.

If i pushed the lever back to the unused position, it would kind of reset and work again, up until i pull harder or drag the brake for longer than a short snappy burst.

I’ve bleed the brake, twice now and it still does this. I then over tightened the caliber bleed nut and had to fit a new calliper (expensive mistake). After two more billed attempts on the new calliper it’s still doing the same thing. The back brake is totally fine, as are the bleeds i’ve performed on my other bikes with XT disk brakes.

No apparent leaks. Is their anyway to work out what’s happening and why?

Any suggestions and help greatly appreciated.

At a guess fluid bypassing the master piston seal.

Sounds like the master cylinder seals are leaking. It won’t necessarily show as an external leak at the brake lever.

What they said, what fluid did you use to bleed them?

Shimano brand mineral oil used.

Is the master cylinder in the brake lever?
If so, would that cause an ever slight liquid squish noise when operated?

Dejavu. This popped up the other day if you search.

Shimano brand mineral oil used.

Is the master cylinder in the brake lever?
If so, would that cause an ever slight liquid squish noise when operated?

Yeah master cylinder is in the lever, there seems to have been a spate of these lately, I would be looking at a warranty claim if they are still under 2 years old, I know of a few who have had them replaced under warranty.

Issues been going on for years

http://singletrackworld.com/forum/topic/shimano-xt-traile-brakes-problem-with-the-lever-any-ideas

http://singletrackworld.com/forum/topic/xt-brake-levers-not-returning

I believe it’s a recognised issue which has been addressed on the new XT, for the life of me I can’t remember where I read it.