"Caroline" <caroline10027remove@earthlink.net> sprach im
news:dX2pd.268$Ua.58@newsread3.news.atl.earthlink. net:


> Brake pistons do freeze in their cylinders, though. I completely
> disassembled my front brakes this past summer. As you can imagine, it
> doesn't take but a little rust buildup on the piston/cylinder walls to
> impede operation.



I find it's more often gum than rust that sticks up the pistons. Rust tends
to invade from the outside, weather being the source. Rust sticks at first,
but rapidly becomes a fluid leak.

Honda, unlike Toyota, uses non-stainless steel pistons. Toyota's are
stainless. Wish Honda would do that too. With Toyota you just clean the gum
off and put it back. With Honda you end up replacing the piston, and it's
not cheap.

One problem with reman calipers is that nobody seems to use silicone grease
on the piston and seals when putting it all back together. They all use
brake fluid as a lubricant because it's cheaper. Silicone grease helps
prevent the buildup of gum and keeps the pistons moving freely for much
longer. Brake fluid dries out and BECOMES gum.

If the caliper is not yet installed, you can just pop the piston out of the
new calipers with some air pressure (even with a bicycle pump with some
electrical tape wrapped around the end to seal it), smear it with some
silicone and reinstall. Observe surgical cleanliness here, by the way,
that's crucial.

If it's already installed, it's a bit more complex:

You can get around this with the judicious use of a syringe from a
woodworking supply store <http://tinyurl.com/6z9j2>, and some silicone
grease.
http://www.tegger.com/hondafaq/rustybrakes/syringe.jpg

What you do is to have a helper step on the pedal as necessary to push the
piston out of its bore most of the way, so the dust boot is mostly
extended. One full pedal push will move the piston about 1/16".

NOTE: ONLY do this if you've been regularly using the pedal-push method of
brake bleeding, or put a block of wood under the pedal so it can't go any
farther than what it does in normal driving!

Use Brakleen or other aerosol brake cleaning solvent to remove the dirt
from the piston and boot first.

Then you ease the syringe under the boot and inject silicone as close to
the hydraulic seal as possible all around the perimeter of the piston. Turn
the piston with a set of channel-locks so you can more easily apply
silicone to the portion that was closest to the top of the caliper. Now
push the piston back in all the way with a C-clamp. Pedal-pump it back out
again and repeat a few times.

When you're done, if the siliconing has been done properly, you should see
the piston move out with a pedal push, but then move back IN again slightly
when the pedal is released.

The grease is just silicone dielectric grease. I use Zip-Slip just because
for me it was easy to get. http://www.themoldersedge.com/polish.htm

Here's another example:
http://www.mgchemicals.com/products/8462.html

Googling for
silicone dielectric grease
turns up many more.


--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/