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From: wa371@sdcc12.UUCP (wa371)
Newsgroups: net.auto
Subject: The worlds best gasket cement.
Message-ID: <231@sdcc12.UUCP>
Date: Sun, 7-Apr-85 05:15:01 EST
Article-I.D.: sdcc12.231
Posted: Sun Apr  7 05:15:01 1985
Date-Received: Tue, 9-Apr-85 01:23:19 EST
Organization: U.C. San Diego, Academic Computer Center
Lines: 40

The best gasket cement is silicone rubber cement.  It is sometimes
sold as bathtub caulk and for other purposes, but it is the same stuff
if it says 'silicone' and is very rubbery when cured.  It will permantly seal
anything, especially such problem areas as valve covers
and oil pans.
The Corvair for example was a notorious oil leaker.  But my Corvair
engine, sealed with silicone rubber cement, never leaked a bit of
oil.
How to use silicone rubber cement:  Clean the mating surfaces of oil
and grease.  Wiping thoroughly is sufficient.  Then apply a thick
film to both sides of the gasket and let it set for about 10 minutes
until it is no longer sticky.  Then bolt the parts together.
The gasket can be omitted altogether.  In that case apply the film to one
of the mating surfaces.
Any color silicone rubber cement will do, but I
prefer white, because that makes it easy to see the thickness of the film,
when I spread it with my fingers.  With correct thickness about 1/16 to
1/8 inch will squeeze out the sides when the parts are bolted togther.
Silicone rubber will withstand up to 500 deg F.  It seals against
all oils, water, air and vacuum.  But it is useless for fuel, because fuel
turns it into a soft jelly.  It is not very strong by itself, and
most oils soften it a little too.  It must therefore be confined between
mating surfaces and have time to cure (one day or more) before it
can withstand greater pressures.
That reminds me:  I once had a hole in a radial tubeless tire, the diameter
of my little finger in the shoulder area, where even small holes can
not be sealed because fo the extreme flexing. 
You guessed it.  Silicone rubber cement to the rescue.  I applied it 1/4 inch
thick over the hole on the inside of the tire after sanding.
Then I let it cure for a week for maximum strength.  I drove on that
tire for another fifteen thousand miles before it started to leak again.
I am sure that a patch over a smaller hole or in a place with less flexing
would have outlived the tire itself. 
This is not a practical way to fix flats on a trip, unless you have
lots of time {:-) --and know how to get the tire off the rim without tools.
(If you want to know how to do that, write to me.)

Bernd 'bear-nd'            *** hooray for USENET ***
(Not affiliated with, nor speaking for U.C. San Diego)
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