Gelled brake fluid in caliper - looking for rebuild kits

[BentRod]

[QUOTE=Nessism;1775540]Sorry to be a jerk and all but this is not true.QUOTE]


definately not a jerk - nothing wrong with correcting someone. I would much rather you do so.

[Shwartz]

I actually took off the rear caliper, connected it to the front brake line (Even with the ensuing air bubble) and used the front fluid to pop a dual-piston setup really far out But not completely).
Then I took the caliper to the bench and wrapped a rag around the edge of the piston (the portion that was sticking out) and gave a gentle twist (spinning the piston within the caliper), again a twist, not a pry! and it just fell the rest of the way out.

I then ordered a new seal and boot for each side. Not sure it needed the new seal as the old one's were pliable but I did need the boot (there was a tiny, tiny, tear) so I might as well have.

[Shwartz]

I actually took off the rear caliper, connected it to the front brake line (Even with the ensuing air bubble) and used the front fluid to pop a dual-piston setup really far out But not completely).
Then I took the caliper to the bench and wrapped a rag around the edge of the piston (the portion that was sticking out) and gave a gentle twist (spinning the piston within the caliper), again a twist, not a pry! and it just fell the rest of the way out.

I also forgot to mention that I cleaned the inside face of the caliper with penetrating fluid and a Dremel equipped with a plastic wire wheel. The wire wheel didn't last at all, but it worked perfectly.

[MOC]

The parts have arrived. If I am feeling a bit better (cold/flu), I will try to make progress on this with some degree of documentation so you all have a point of reference. The brakes haven't been opened in 29 years, so I expect quite a bit of cake batter to come out when I crack them open. thanks for the help.

mike

[chuck hahn]

The most critical aspects are the groove the seal goes in...mjust be as clean as you can get it. Next, the piston..no chips, gouges, or rusty pitting anywhere on the edges that contact the seal. If theres some brown stain and a tad of rusty wear in the piston sump of the caliper it will be just fine. But under no circumstances do you want any damage to the piston itself on the sides.

[MOC]

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)

[chuck hahn]

What ya soaking them in???

[MOC]

acetone. so far so good

What ya soaking them in???

[MOC]

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.

[chuck hahn]

I wont even venture a guess till I see the pics...

[MOC]

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.

[MOC]

video of the piston:

http://www.youtube.com/watch?v=vIDyQ4Mkzww

[chuck hahn]

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!!

[chuck hahn]

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.

[MOC]

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...