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I left my bike in the car for a couple of hours and one of the brake levers has leaked onto my bars, I can see a residue from around the master cylinder cap. Is this likely to be a failed seal, or do Hope race brakes not like being left on their side for a few hours? This is on a second hand brakeset that I have stripped down and bled, everything seemed okay with it but something needs attention I think.
Check around the fill hole to make sure it's completely clean with no residue or gunk on the metal mating surface. The seal should draw air in above it as the pads wear but not let fluid out. Other than that it could be seals on the master cylinder piston?
From what I can tell it's coming from the cap area. I'll try taking it apart, cleaning and re-assembling.
Yes, that wee hole is a right pain, if yiyve had the top cap off lately chances are it's that, take it off and put back it again and repeat until it's right!
On the Tech lever I've found that the master cylinder diaphragm can easily get deformed, whereby the long edges warp inwards and stop sealing properly. I always keep spares now (they're about a pound or something) and check to see they're ok at every bleed.
The other thing that's caught me out in the past is if I'm a bit clumsy with the brake fluid and let it get on the top of the diaphragm when reassembling. If this happens then that fluid will weep out of the little hole in the cap over time. This doesn't have any effect on braking performance but does get my OCD sensitivities twitching!