jeff costello Posted May 17, 2015 Report Share Posted May 17, 2015 i was adjusting my brakes today, when suddenly my hs33 2014 carbotec lever stopped working. piston just went in, didn't come back out on its own, no more brake power at all. so i decided to open up the lever body to have a look at the internals. brake froze a few times during the winter, i guess that didn't make things better. fluid was water only. now i'm this far. what do i do now?? i tried pulling out that thing on the bottom with pliers, but that didn't work. do i need a new lever? Quote Link to comment Share on other sites More sharing options...
AdamR28 Posted May 17, 2015 Report Share Posted May 17, 2015 Fit a pump or air line to the hose and blast the piston out. It will be swollen with the water, it'll dry out if left in a warm place for a few days, or you can lathe 0.1mm off the diameter. Quote Link to comment Share on other sites More sharing options...
jeff costello Posted May 17, 2015 Author Report Share Posted May 17, 2015 thanks! i only have a cheap pump. i could fit it reasonably well to the lever, but it only generates about 4bar, so i have to think of something else. what's in there that can swell? Quote Link to comment Share on other sites More sharing options...
Mark W Posted May 17, 2015 Report Share Posted May 17, 2015 The piston itself is what swells - it's just due to it being made out of a hard plastic that absorbs water. If you use antifreeze you can slightly reduce that happening but also stop your brake freezing in winter. Quote Link to comment Share on other sites More sharing options...
jeff costello Posted May 17, 2015 Author Report Share Posted May 17, 2015 thanks. i'll let it dry for a few days, then try again to get it loose. Quote Link to comment Share on other sites More sharing options...
jeff costello Posted May 18, 2015 Author Report Share Posted May 18, 2015 hello again, thanks to your ingenious method of using the pump, i got the piston out. is there anything i should do before putting it back together? lube? sorry for being a bit dim-witted here, but there's basically nothing to find online about those new magura levers. Quote Link to comment Share on other sites More sharing options...
forteh Posted May 18, 2015 Report Share Posted May 18, 2015 I had this problem as well, took 120psi from my track pump to shift it I mounted the piston in my drill and used fine emery paper to take a fraction off the outside diameter as adam pointed out. I'm not sure adam is correct with the swollen nylon piston reducing after leaving it to 'dry out'; the material absops the water and swells, I believe this is a one way process although happy to be proved wrong I took just enough off the diamter to make it a nice sliding fit in the bore of the cylinder and not had any issues since. Quote Link to comment Share on other sites More sharing options...
AdamR28 Posted May 18, 2015 Report Share Posted May 18, 2015 the material absops the water and swells, I believe this is a one way process although happy to be proved wrong The reading I've done suggests it will dry out, and we've had a few customers have this work for them too, maybe it depends on grade? Water rapidly attaches to or detaches from its surface until it is in equilibrium or balance with it's surroundings. With nylon 6 that is about 3% moisture at 55% RH. that goes up to 9% at 100% RH and down to zero at zero RH. Quote Link to comment Share on other sites More sharing options...
jeff costello Posted May 18, 2015 Author Report Share Posted May 18, 2015 ah, so the swelling is (might be) a permanent thing? hence the need to make the piston smaller... ok i think i get it. i will try lube first - just in case it was just some calcium or similar that was in the way (brake was unused for quite a while). if that doesn't help, i'll try and sand a bit off. Quote Link to comment Share on other sites More sharing options...
AdamR28 Posted May 18, 2015 Report Share Posted May 18, 2015 Lube won't work unfortunately, it needs to be made smaller (or use mineral oil). Quote Link to comment Share on other sites More sharing options...
jeff costello Posted May 18, 2015 Author Report Share Posted May 18, 2015 (edited) what about the dot-fluid? i still have some of that. edit: i put it back together and it seems to work again with some lube. haven't hooked it up to the brake hose yet (running the spare lever right now). we'll see. i will probably invest in a better quality lever soonish. what's a better product these days? racing line? clean? Edited May 18, 2015 by jeff costello Quote Link to comment Share on other sites More sharing options...
forteh Posted May 18, 2015 Report Share Posted May 18, 2015 Big no no to dot fluid, it will ruin the seals. Just machine it down slightly and you won't have the problem again because when the piston swells again it will be smaller to start with Quote Link to comment Share on other sites More sharing options...
jeff costello Posted May 18, 2015 Author Report Share Posted May 18, 2015 thanks! will do that when the problem arises next time. Quote Link to comment Share on other sites More sharing options...
dngr2self Posted May 18, 2015 Report Share Posted May 18, 2015 I rubbed my piston down bit by bit with wet and dry when it happened to me. They usually work quite a while though so I wouldn't be in that much of a hurry to replace it if I were you. You could always just buy a couple of replacement pistons though for if it does happen again as a cheaper alternative to replacing the full thing. Quote Link to comment Share on other sites More sharing options...
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