(Another) Sleeve stuck on piston - Page 4

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JohnB.
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#31: Post by JohnB. »

Could be the piston unscrewing a bit on the rod end but also could be the rod unscrewing some at the top. Easy fix either way if you have a pin wrench & if you can get up into the group with the wrench. If not you'll have to pull the piston/spring assy. again & tighten it on the bench.
LMWDP 267

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Balthazar_B (original poster)

#32: Post by Balthazar_B (original poster) »

IamOiman wrote:A Caliper tool would be my best bet on getting the piston to normal resting height again. I am not sure what else could cause this outside of the piston beginning to unscrew from the rod (which can be very bad if you happen to somehow unscrew it fully). You could trying rotating the whole upper group clockwise a few times to see what happens but usually with that spring it takes a little oomph to tighten/loosen the piston. I would hold the upper group while turning the brake caliper tool.
Think it can be done with the machine fully assembled (with the screen off, of course)? It would mean the piston rotating within the sleeve, but it shouldn't take very many turns -- facing the bottom of the piston, that would be clockwise, I reckon -- to adjust back to flush.

OTOH, maybe I'll want to know whether the spring it turning (it didn't when rotating the lever head)...
- John

LMWDP # 577

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Balthazar_B (original poster)

#33: Post by Balthazar_B (original poster) »

JohnB. wrote:Could be the piston unscrewing a bit on the rod end but also could be the rod unscrewing some at the top. Easy fix either way if you have a pin wrench & if you can get up into the group with the wrench. If not you'll have to pull the piston/spring assy. again & tighten it on the bench.
Makes perfect sense. Thanks, John!
- John

LMWDP # 577

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Balthazar_B (original poster)

#34: Post by Balthazar_B (original poster) »

OK, piston problem solved as well. JohnB helpfully suggested I just pull the piston again and tighten it using needle nose pliers in lieu of a pin wrench. Did so and everything back as it should be. Didn't mention it earlier, but although the Bosco seals seemed mostly OK, a couple of them weren't perfectly smooth in small spots, so decided to proactively replace them and avoid any related issues before I re-lube next year. I got a set of Cafelat blue Modern Lever seals, which went on very easily, and my test shots went great. The action is somewhat smoother and the seals appear to be working extremely well. It'll be interesting to see how they do over time, and if they can match Bosco seals for longevity.

A couple of lessons learned:
  • To help with piston removal, next time I relube, I'll begin by compressing the spring, applying some lubrication up in the sleeve, then working the lever a couple of times to make sure the seals are slippery, and then pull off the lever head. Normally water is the lubricant, but on a cold machine with very viscous lubricant (in this case Loxeal 4), seems like there'll be some risk of the piston not wanting to let go of the sleeve. Maybe the more pliable Cafelat seals will behave differently, but it's an easy thing to add to the workflow.
  • I'll put together a little jig to use if I see this piston stick issue in the future. It needs to be 2 pieces that wrap around the spring and provides surfaces for the top of the sleeve and the bottom of the piston head. When in place, this will enable a pull of the lever to extract the piston from the sleeve if it's stuck. The quick and dirty way to secure the jig would be to use a metal mounting strap, but maybe I'll get fancy by using a hinge and latch instead.
Thanks to everyone for their thoughts and recommendations. Much appreciated!
- John

LMWDP # 577