(One more message that might be a duplicate due to sending problems)
Answering your questions about silicone and o rings. Long response so I
am publishing it to the list also.
I use o rings around any 3/8 or 5/16 bolt that has oil behind it. I use
a countersink to cut a ridge for the o ring to sit in. As I tighten the
bolt the o ring does a great job of sealing the bolt and as a side
benefit it seems to never rattle loose. It is great for bolts on the
engine or trans. Recently I have seen washers manufactured with o rings
installed on them. This saves plenty of trouble. I have no source for
these washers. I am just recalling that I saw them on a new car that I
was taking apart and they were a most clever innovation.
On the subject of silicone, you can use silicone in place of a gasket.
The question one needs to answer is how much pressure is behind it or
between the parts. Perfectly flat surfaces do not need a gasket or
silicone or anything. Imperfect surfaces or surfaces that warp and
distort needs a gasket or something to fill in the gaps, paper, cork,
copper or glue do the job. For a cylinder head - using silicone? I would
expect failure and use silicone for this only out of desperation. Maybe
a good case would be if I were forced to reuse the old gasket. Silicone
is soft and subject to heat. Using it on exhaust manifolds is also
unlikely to be a happy choice.
For an oil pan I would first make certain that the piston rings were
good and no gases were getting past the rings. Worn rings will always
result in leaking oil around the valve cover and the oil pan, any
engine, any car.
The problems with the aluminum sump might not be the gasket. It might
just appear to be the sump pan gasket with the oil coming for a higher
source.
You might want to do what I do. Jack the car up, dry everything and
watch for leaks. I find this takes over 8 hours of patient waiting and
maybe having to do it again the next day.
I recall oil leaks on my 6's. The valve cover was always a challenge and
it being on top of the engine, it is easiest to diagnose. Eventually
getting that under control, the distributor needs to have its o ring
changed every now and then. The upper end being under control, then
focus on the oil canister and replace it with a Jack Walker spin on oil
filter or replace all the oil seals on the original oil filter. I add a
3/8 o ring on the shaft inside and between the spring and the can. At
the same time I add a flat washer pushing the o ring to form a seal
inside the can. Few people know all the seals in that "can filter
thing."
Next look at the tappet covers and put new fiber washers around the
bolts with silicone around all the gasket surface parts. Just a light
coat seals these parts, no need to really goop up the stuff. Then take a
look at the oil pressure adjustment points. A light coat around the bolt
cover might be useful. Keep in mind I am trying to recall the 6 engine
from memory and might not be describing the necessary points correctly.
(Oh yes the parts catalog I get every 6 months in the mail, show the
parts numbered 103 thru 105). Also check the oil tube going to the oil
pressure gauge; this might need new washers or replacing.
Now that I see the cork strips in the parts catalog pictures, I would
cut those down and use silicone glue around all surfaces. But what you
describe should have worked.
With one car I resorted to using contact glue on the oil pan. Ah yes,
all four surfaces. Really sealed that stinking thing. However it was
later challenging to remove again, it was almost like using liquid
steel, if you can imagine that. (I was 14 years old.)
Upon review of the 6 engine parts in the parts catalog, I have to
believe that some of the leaking is coming from the front and rear cover
plates. To me it appears there is oil behind these plates, otherwise
there would be no need for gaskets.
I guest the short answer is to do a compression test. Prove the rings
are good, pull the engine and replace all gaskets, coat them all lightly
with silicone, just enough to develop a sticky feel. Avoid using too
much silicone and watch how much it squeezes out the sides; just the
tiniest squeezing out is fine as that much goop also goes inside.
This is a good time to fix engine paint and while you think of that
procedure I wish good luck to your body paint during engine R&R.
Yes, kind of a long response, but this is what I recall about sealing
the 6 cylinder engine.
Let me know what you find.
Best Regards,
Jim LeBlanc
Nearly dry 100-4
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