Why do some engines use RTV sealer instead
For a period in the 1980s, domestic auto
makers thought they could lower production costs and improve sealing
by using RTV (Room Temperature Vulcanizing) silicone instead of conventional
cut gaskets to seal valve covers, oil pans, timing covers, transmission
pans, and other parts. In theory, the idea made sense. By applying a
thin bead of RTV to such parts, they could be assembled and sealed in
Engineers liked RTV because it does not take
a set like a conventional cork/rubber cut gasket. Heat causes a cork/rubber
gasket to harden and become brittle with age.
To seal properly, RTV requires both surfaces
to be clean, dry and oil-free. Though installers use RTV all the time
with no problems, car makers apparently could not keep their parts clean
enough on the assembly line to produce a lasting seal with RTV. They
found they were having more oil leaks, not less, with RTV.
Eventually, domestic auto makers dropped
RTV in favor of molded silicone gaskets which combine the installation
ease of a conventional gasket with the sealing properties and durability
When working on an engine that has RTV instead
of gaskets, the installer can either use RTV to reseal the engine, or
replace the RTV with conventional cut gaskets. In some applications,
longer bolts may be necessary to compensate for added gasket thickness.
Some prefer to use RTV because it eliminates
the need to stock a lot of different gaskets. Others prefer to substitute
a cut gasket because of RTV's limitations. Care must be taken when using
RTV so excess sealer does not seep out from between the seating surfaces
and end up someplace where it does not belong.
RTV takes 30 minutes to an hour to set up
(full cure takes about 24 hours). The vehicle should not be driven during