Shimano SLX stopped working suddenly...

WalterWhite

I was mid way through the Cannock Chase Monkey Trail yesterday when my front SLX hydraulic brake just stopped working.

The lever felt no resistance at all, and even at full braking it was just skimming the disc surface.

I expected to see hydraulic fluid all over the place but both ends of the line were bone dry? No signs of leakage and it was working 100% before then.

The brakes were fitted around a month ago and I've done this same trail 3 times on these same brakes with no issues, but all of a sudden I just lost the whole front brake? I carried on but this made it a little scary in some places! I haven't took the brakes apart yet to have a good look bit what could cause this? Air in the system somewhere?

Any help would be great!

JGTR

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19702089#p19702089]WalterWhite[/url] wrote:

I was mid way through the Cannock Chase Monkey Trail yesterday when my front SLX hydraulic brake just stopped working.

The lever felt no resistance at all, and even at full braking it was just skimming the disc surface.

I expected to see hydraulic fluid all over the place but both ends of the line were bone dry? No signs of leakage and it was working 100% before then.

The brakes were fitted around a month ago and I've done this same trail 3 times on these same brakes with no issues, but all of a sudden I just lost the whole front brake? I carried on but this made it a little scary in some places! I haven't took the brakes apart yet to have a good look bit what could cause this? Air in the system somewhere?

Any help would be great!

Check for visible leaks, which you've done, then next step is to try and bleed them

Antm81

How does the lever feel, does it pull all the way to the bar or is it still firm?

If it's still firm a bleed won't solve anything.

WalterWhite

Thanks guys, the lever goes right back to the bar with almost no resistance at all...

It's wierd that it was fine for the first hour, then suddenly stopped working but with no signs of oil leakage anywhere...

dusk

Did you check the piston? You're most likely to lose fluid from the round one of the pistons rather than the hose.

step83

Effectively with the brakes your shoving a piston into the reservoir to displace fluid so the calliper shuts. Its more technical than that but thats a basic way to look at it. If the callipers no longer moving an the lever is loose I would suggest either a leak as mentioned. Air hole in the seal around the reservoir cap or you have a problem internally on the brake.

Take the plastic body from the top to check theres none hiding under it and also make sure the grub screw washers tight on the filling port. Brakes are designed to be a sealed system.

The Rookie

An acquaintance had an XTR lever fail where the fluid was leaking back from the pressurised cylinder into the unpressurised reservoir, no external loss of fluid, but a lck of brakes, there was some resistance to lever motion but negligeable and it pulled back to the bars.

It could also be a mechanical failure (no connection from lever to piston) but the n I'd expect the lever to be 'floppy' and not self return.

WalterWhite

Thanks all I'll have a good inspection tonight!

Dirtydog11

Sounds like the master cylinder seals have failed!

Have they been bled and if so with what fluid, Magura mineral oil (Blue Blood) will kill them as will DOT.


Providing you haven't done either of the above they should still carry a 2 year warranty.