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If your thermostat housing and mating surface on the head are relatively
smooth but it still leaks one thing you can do that will help is increase
the pressure on the gasket by lapping some off the housing surface.
(sometimes the housings are warped so they are smooth but not flat -
this treatment will help that also)
Put a piece of about 150 wetordry paper on a flat surface, like a tablesaw
table, etc and lap the faying surface of the housing, preferably in the
direction of a line that connects the bolt holes. Good to do most of the
lapping in the one direction until you are lapping the whole surface.
Once you get the surface cleaned up, put the thermostat with seal ring
in place and see if the seal ring stands up above the surface. Probably
0.020-030" is enough. That will make your housing press the ring tight
enough to make it seal. If it doesn't show above the surface, turn
the housing so that you are lapping at some angle to the previous direction,
maybe 45°, and lap some more. If you have a long way to go, you might want
to either use coarser wetordry or get a different housing. In any case,
if you can't clean up the corrosion, don't use the housing. They are plentiful.
When you install, just tighten the bolts enough to hold the housing flush.
If you tighten them too much you will bend the ears of the flange down and it
will NOT seal. (sort of like oil pan bolts)
Putting a gasket between the housing and the head is counterproductive
because it reduces the pressure on the seal ring, and the seal ring is
VERY effective when used properly, better than a paper gasket. Even an
old seal ring will seal fairly well if not cracked or squashed too thin.
--
George Downs Bartlesville, Heart of the USA!
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