LEAKING BRAKE PROPORTIONING VALVE - 1986 4KQ

["Dean and Heather Sutherland" <hsutherl@nbnet.nb.ca>]

The proportioning valve on my '86 4000 Quattro leaks brake fluid from a
recess at the front of the casting.  (Some call it a pressure regulator too
I believe, but in any event I'm referring to the casting that mounts
directly beneath the master cylinder).  This "recess" is a hex shaped
indentation with a small cylinder shaped protrusion inside, which is where
the fluid appears to come from.  This is more of an inconvenience than
anything since the brakes continue to work fine.  Since the dealer wants
$303 Cdn (gasp!) for a new valve, I'm wondering if it would not be possible
to simply plug the recess from which the fluid is weeping.  By "plug" I mean
for example filling this recess with a sealant such as silicone (or whatever
product might be compatible with brake fluid).  I realize this would be
somewhat of a "band-aid" approach, but  I'm trying to keep the old girl on
the road as economically as possible and I don't want to spend over $300 on
a part if I don't have to.

In case the overwhelming response from the list if "Oh my gawd don't plug
that hole fool"!, I'd also appreciate any advice on vendors that might offer
a better price and any "do it yourself" advice you might have for replacing
it .  Thank you.