Rebuilding brakes is a somewhat simple, but meticulous task. I will offer
a few general hints on the hydraulics. [About 15 minutes later...] Wow,
I didn't realize I was going to be so long winded here. OH well, I hope it
helps a few folks get some decent stopping power. I ended with "bleed the
system", which I hope needs no furtehr explaination. I'm getting tired of
typing!
mjb.
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Lay in a good supply of Castrol brake fluid. Unless you decide to try some
silicone fluid, in which case lay in a good supply of that stuff. And it may
be cheaper to buy in large containers, but for home use having many fresh pints
is better than one stale gallon. It doesn't really get "stale", brake fluid
will absorb mositure and airborne contaminants over time. Things that rust
and rot the system.
Try to get the cylinders as clean as possible before dismantling anything.
An old toothbrush and some spray brake cleaner will help. Be careful not to
splash nasty chemicals all over while spraying and scrubbing, though, use some
caution.
Take apart wheel cylinders one at a time. This is actually a bit of advice
which may be helpful in several areas. If you have two of them, or a left and
right, having one of them still mounted and intact can give you valuable hints
on how the other should be reassembled and mounted. Having nothing but two
of each part scattered about the workbench may lead to nothing but confusion.
Once the cylinder is apart, clean out the inside and take a look. There will
be corrosion around the end where the cylinder bore is exposed, but the inside
where the seal has been running should look pretty good. If really scratched
or pitted buy a new one. The old one will leak again real soon if "fixed."
The best way to clean up the finish of a cylinder will be with a small honing
stone. The corner parts store probably has hones which fit in a hand drill,
but don't fit in you dimunutive 5/8" cylinder bore. Check to make sure the
hone will be small enough to work. Mac Tools makes a nice honing kit that
will make a 1/2" hone, but you have to find a Mac Tool truck to buy one.
When honing, do it gently, and use a good splash of lubricating fluid. For
aluminum, I usually use kerosene as the lubricant. Well, to tell the truth,
I usually use charcoal lighter fluid from the barbecue supply shelf, as it is
mostly deoderized kerosene. Hone a bit, then look at the surface. You don't
want to remove too much metal, so be careful, only hone enough to clean up
the bore. Check it by dipping your clean finger in the small cup of clean
brake fluid, which you have just for this purpose, and feeling the surface of
the cylinder. It should feel and look smooth and clean.
After honing, spray out the inside of the cylinder with s shot or two of brake
cleaner, than swab it generously with clean Castrol. If you have either an air
compressor or access to an ai tank and a blowgun which can be attached to it,
blow out the cylinder with a blast or two of air before swabbing it with the
fluid. Slop some more Castrol on your fingers and put the new seal on the end
of the previously cleaned piston. Make sure the lip is facing the proper
direction. Usually you want the wider, expanded end to face towards the closed
end of the cylinder, so that the pressure of the fluid behind it forces the lip
into a tighter seal. The point of assembling the seal with damn slippery brake
fluid all over your fingers is not to entertain any onlookers, but to keep your
finger oils from possibly starting a bit of rot on the edge of the seal.
Okay, so now you have a clean, rebuilt cylinder. Install a new bleed nipple,
after applying some anti-sieze to the threads. This will prevent the new one
from corroding into place and snapping off like the old one did, which was what
necessitated the rebuild in the first place. But if you managed to get a good
one where the bleed nipple actually came out in one piece, clean the tapered
seat with a Scoth-Brite pad, blow it clean, inside and out, then install with
the anti-sieze. Make sure the bleed nipple goes into the proper hole, the one
with the taper to match the end of the nipple. The other hole has the taper
going the other way, and is made to fit the flare on the end of the connecting
pipe. Reversing the location of these two will be evident in the first good
application of pressure to the system.
Also apply some anti-sieze to the threads of the pipe fitting which attaches to
the cylinder. Install the cylinder, attach the pipe and move on to the next
cylinder rebuild, or finish up the installation and bleed the system.
mjb.
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