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Just bled my Deore 615 front brake*, which was pulling to the bar...
All that lovely pink mineral oil has turned into ugly black sludge. Does this generally mean death by seal failure?
* purchased February 2017 🙁
Probably not. My brakes are always full of crap when I bleed them, hardly surprising when they spend most of their life covered in mud.
I thought they were supposedly a sealed system? If crap is getting past the seals into the mineral oil, then oil under pressure must be going in the opposite direction? They're still only half-heartedly grabbing and squealing in protest, so it was either a really crap bleed on my part or they are borked.
If they are a sealed unit, why the need to bleed?
suspect some contamination but they’ll work fine.
If they are a sealed unit, why the need to bleed?
suspect some contamination but they’ll work fine with new pads
If they are a sealed unit, why the need to bleed?
True...
Still a bit paranoid about sticking new pads in them - they'll spray them with oil as a parting '**** you' on the way to the little pile of dead shimano brakes I've collected.
I doubt it, probably just in need of fluid replacement.
Theyre still under Shimano’s 2 year warranty so you’ve little to fear.
Have you bleed them before? They don’t like some mineral oil. Halfords ‘Bike Shed’ stuff killed my XTs
I've used proper shimano stuff - I'll have another crack at them later to check I've got all the air out. Tempted to slightly overfill them as they always feel rock-hard against the bleed block but a bit pathetic once you've got the pads back in.
For some reason I thought the 2 years was just XT and above, so that's good to hear.
The fluid goes "dark" because tiny bits of alluminium are polished off the inside of the piston bores (in the master cyl and the calipers) by the rubber seals every time you brake! A tiny amount of material can make the fluid go dark, generally it's nothing to worry about, and normally reduces significantly after a while as the bores polish up and stop wearing as much!