re: brake rebuilding

["Giller,Bruce C." <bgiller@domain.elided>]

> While I was there, I asked for a brake rebuild kit for my front
> calipers.  They didn't have a "kit" in stock, but they helpful guy
> behind the counter pieced on together for me.  It looks to consist of 2
> brass-colored metal rings, 2 black metal rings, 4 round piston seals and
> 4 round dust caps (the counts are correct; I'm guessing on the
> descriptions).  I've never been through a caliper rebuild and have no
> instructions included with the parts.  Furthermore, the print on my
> manual is so bad that I can't see the pictures for the caliper assembly,
> and the text is minimal.  Can anyone walk me through rebuilding the
> calipers (I have an extra set - thanks again, Brian!) and swapping them?

Hal,

	I just recently rebuild the front right caliper on my '73 GTV since one
of the pistons was sticking.  The rebuild kit from the local Alfa
ex-dealer was from ATE.  It had two rubber dust covers, two rubber
piston seals and two metal rings where the ends overlapped slightly.  I
have since bought 3 more kits for the other calipers since this one was
in such sad shape.  Do NOT separate the caliper since your rebuild kit
doesn't include the O-rings for those hydraulic connections between the
caliper halves.

Removal:

	First, remove the caliper from the car (this essentially drains the
front brake line so get a can to catch the drippings).  Use some brake
cleaner to clean off the caliper; you don't want to get dirt and grime
inside the caliper.  Remove the ratty old dust shields and the metal
rings that hold them in place.  Next step is to remove the pistons.  Use
a C-clamp to hold one piston in place and apply compressed air where the
hydraulic brake line attaches to the caliper.  The other piston should
pop out; sometimes you have to position the C-clamp so that it doesn't
interfere with the piston when it comes out.  To remove the other
piston, you need to seal off the hole where the first piston used to
reside.  I used a flat metal plate I had lying around that would covered
the hole and held it in with the C-clamp.  A bit higher psi was required
to pop it out since there was some leakage.  Remove the rubber piston
seals from inside the cylinders.

Cleaning:

	Use your brake cleaner (don't use anything else but brake cleaner) to
thoroughly clean out the caliper drillings, piston cylinder, and the
pistons.  I had to scrape out some hardened spooge.  Check the pistons
for pitting on the sealing surface; not sure if you can get replacement
pistons.  Make sure all the gunk is removed especially in the groove
that holds the piston seal.  Check out the hydraulic drillings to see
that they are not partially clogged.  Clean out the groove on the top of
the piston cylinder where the rubber dust boot will be placed - usually
just rust in there. Remove the bleeder valve and coat threads with
anti-seize so that you won't have trouble with it later on like it
shearing off....

Rebuilding:

	Coat the piston seal groove with either brake grease (just where do you
find this stuff??) or brake fluid.  Insert the piston seal making sure
that it hasn't twisted on you.  Coat the outside of the piston with
brake grease/fluid and the outside of the piston seal, then insert the
piston into the piston cylinder - I was able to push one in by hand but
the other required I used the C-clamp to push it all the way in.  Next
put the rubber dust boot on and then the metal ring that holds it in
place.  Repeat for the other piston.

	Loosely bolt caliper back on the wheel, attach hydraulic line, torque
down caliper bolts, insert brake pads and anti-rattle clip.  Don't bleed
the system until you had done both calipers.  If it has been awhile
between brake fluid renewal, you might want to go ahead and flush/bleed
the entire brake system.

	Once you have bleed the system, check to see if you have any leaks -
check where the hydraulic hard line is attached to the caliber and the
lower part of the caliper if the piston seals are leaking.  Drive around
for a bit and check again.

	Bruce

	'73 GTV
	'86 Spider
	'72 Moto Guzzi Eldorado

	Takoma Park, Md

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