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Gelled brake fluid in caliper - looking for rebuild kits

  • Thread starter Thread starter MOC
  • Start date Start date
got the piston out, removed the old seal and boot, and there is a bunch of solidified sludge in the base of the seal groove, as well as stuck to the base of the piston. There wasn't too much varnish on the metal to metal surfaces which makes me feel bettter, and the lumps aren't as big as i expected. i've got the parts soaking right now, and hopefully will have time to get a better look tomorrow. tossing around the idea of using a very mild abrasive in the groove (wet baking soda and a toothbrush) to take off some of the varnish that's built up. i've used it on other projects of this nature and it is juuuuust enough to get the job done without overdoing it. (works great on gun parts for those of you who are so inclined)
 
I got the parts out of the bath this weekend and was preparing to reassemble everything, but upon further inspection I've hit a snag. There is a 1 mm wide groove about 5 mm in length running perpendicular to the piston's path of travel, about half way down it's length. It looks like it was machined into the metal, but it's not in a place I would have expected such a groove to be. The rest of the piston is immaculate and clean. Any thoughts of if this is supposed to be there?

When you test fit everything together it looks like this groove would be just shy of interfering with the seal when the pads are fully worn down, so I am confident it's never really seen the light of day. not sure what kind of wear would have caused this.

I will try to get a picture of it up tonight.

as usual, your input is appreciated.
 
At second glance its definitely corrosion. Not sure how it got there but I'm going to replace it nonetheless. I see lots of talk about stainless replacements, so I'm assuming that's what you will suggest here.

Once again, parts resources would be greatly appreciated. Is Z1 a good resource for brake parts? Thanks for the help.
 
yeah...that psiton is just a catfishing weight now!!! The scar probably got there from it being extended out of the seal a long way and then sitting in a moist environment for a good time. Water will get under the dust boots via direct absorption in the rain or simply from humidty cycles. In any case, if the brake pistons are not PERFECT then they dont belong in the very thing thats relied upon to stop the bike and save your life!!
 
Got any buddies that work in a machine shop with a lathe?? Use that to take measurements and spin you off some stainless ones? May cost you a few bucks for some bar stock..but will probably be less than buying new ones.
 
doubtful. i don't think i'm going to find a machine shop around here that will mill me something to those tolerances out of stainless for any price worth taking. i'd rather just buy the oem replacement. at least that way i'm getting something i KNOW will fit. anybody have experience sourcing custom stainless parts? i'd make it myself but i don't have a lathe...
 
Hey was worth a shot..right? Someone who has a lathe can for sure turn them quite easily..not a whole lot of precision details there!! HA HA. And even the groove for the dust seal doesnt need to be very critical!! Overall diameter and length are the critical points here. Could even make them hollow core style too and leave the wall thickness about 1/8 to 3/16 inch and shave off some weight there as well.
 
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