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I recently had my C85 rebuilt. After the rebuild on three occasions I
found
that I start the plane up - the oil pressure is fine. I fly around for an
hour and oil pressure is fine - I land some where and have lunch. After
lunch I restart the engine and the oil pressure is 0!. The oil pressure
does not come up.
It appears that if the plane is allowed to sit overnight the oil
pressure will come up and be normal. Needles to say this is very
disturbing
and I am looking for advice.
Here are the facts. In the rebuild the mechanic was concerned about
corrosion in the accessory case but had a company machine it and replaces
it. Hr replaced the gears on the oil pump. We also replaced the oil sump
with an 0200 sump (6 quarts instead of 4 ). I will commonly fly with 5 or
even 4.5 quarts in the sump.
The problem never happened before the engine was rebuild even though
things were loose enough that when the engine was warm the oil pressure at
idle would be in the 5-10 psi range and at cruise would drop into the
20-30
psi range as the oil warmed.
My mechanic thinks the oil pump is losing prime as the thin, warm
oil
leaks out from around the pump. I am not sure but cannot offer any other
explanation. The last tome the problem occurred I had the local mechanics
take off the oil filter and the cover to the old scree on the accessory
case and squirt in oil and nothing happened - leading me to wonder whether
loss of prime is a good explanation.
Oh yes - I have never had problems when I stop for a short time -
long
enough to refuel, for instance. It takes a stop of about an hour - enough
for lunch. Once the oil pressure comes up it stays at 40 PSI without a
whimper
Any ideas????
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