Rear Caliper piston rust

james accordino ssgacc at
Fri Jul 4 09:05:16 EDT 2003

I'll take a stab at this.  Are you reusing the rotors?
 If the static position of the piston rust belt is
beyond the square o-ring, you'll be fine.  As the pads
wear, the rust will move farther away from the o-ring.
 IME, that's been the determining factor.  It appears
your piston rust is a result of the boot being torn
and maybe some channel lock knaw marks as it's on the
outer end.  Heavy contamination of the brake fluid
results in rust much farther down the system.  If the
portion of the piston that traverses the o-ring is
knackered there's a good chance it'll leak.  It sounds
like you've already got the seal kit.  I'd give it a
shot.  Lube the o-ring well and maybe smear a healthy
dose of anti-seize around the top of the piston under
the rubber boot.  I think it'll be fine.

Jim Accordino

--- Kneale Brownson <knotnook at> wrote:
> I noticed while replacing the pads on the rear
> brakes of my wife's 4kq
> camping car that the rubber boot on the caliper
> piston was torn, so today I
> took the caliper off to install new rubber bits.  I
> found that the piston
> had a ring of rust right on the chromed edge next to
> where the rubber boot
> fits.  That was easy enough to remove, but there
> were a couple spots on the
> chrome where there were rust spots maybe as much as
> a quarter inch down the
> chromed surface.  I tried smoothing them out with
> one of those flat files
> they used to use to file ignition points.  That took
> the sharp edges down,
> but there's some rust pitting I couldn't get to.
> Will these rough spots  tear up the rubber seal in
> the caliper cylinder
> ID?????  Should I be looking for some new calipers?

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