Re: Dan's Master cylinder

[jlandry@domain.elided (John A. Landry)]

In a brilliant stroke of genius, Chris & Ranae Procyk <procyk19@domain.elided>
blurted out:

>I am forever frustrated by the fluid seeping out around the caps
>of the snap-down type.

A handy Landryesque tip to prevent (or at least substantially reduce) the
seepage...

When you buy a rebuilt master cylinder, you'll notice the sealing lip is
usually worn and not perfectly flat.  This metal surface has usually been
sand or bead blasted during the rebuilding process and most likely contains
small nicks and dents from handling and storage.  If the rubber gasket on
the lid is otherwise new, this is why the brake fluid seeps from the under
the cover.

I take a sheet of fine wet type finishing sandpaper (maybe 200 to 400 grit)
or fine emory cloth, and lay it grit side up on a smooth flat surface.  A
12" square of 1/2" thick AC plywood is smooth enough, but a piece of steel
plate is even better.  The newly rebuilt master cylinder is then inverted
onto the sandpaper and rubbed (polished) in random directions.  In a few
minutes the sealing lip will be polished flat and smooth.  I keep going at
it until any nicks or dents which would hinder proper sealing are
completely polished out.  Depending on the sandpaper grit you started with,
you may want to switch to a very fine finish grit for a final smoothing.
Afterwards, the master cylinder needs to be carefully cleaned with
compressed air and denatured alcohol to remove any trace of grit or
powdered metal.

I did this on the last master cylinder I bought, and it doesn't seep a
drop.  The sealing lip is smooth and flat after the treatment.  The outside
of the master cylinder has remained perfectly dry.

Regards,

John L.
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