This is probably old news to you and I'm not looking for advice or help; just
passing
on my observation. My engine has around 300 hours and is going just fine
with four similar compressions, apparently making as much horsepower as ever.
Only thing is that it has usually needed quite a lot of rotations when
gurgling/burping,
to push oil back into the tank. But not always!
Somehow I came to realise that infrequently the oil level would stay unchanged
near the top of the dipstick flat for days on end. Mostly my experience has been
that the oil would sink away overnight down to about 1/8 inch below the flat,
then never go lower no matter how many days passed until the next flight.
It seems to me that the difference could be caused by siphoning of oil out of
the
tank after flight, which stops once the siphon is broken when the level in
the tank gets below the end of a metal tube, perhaps? Or that the siphon can't
be sustained after an air bubble from the crankcase finds its way up an oil
hose?
This might account for the oil generally not dropping below a certain level
as seen on the dipstick, except when I choose to do the gurgling/burping after
flight!
Sometimes, in fact rarely, I perform the gurgling/burping around and hour after
flight, say because I might have elected to top up the oil level before going
home. I can only imaging that the siphoning would have been going on during that
hour until I started turning the prop by hand, which in that case takes very
few rotations to hear the gurgle/burp telling me that air has been pushed back
up the hose. This air could prevent siphoning.
Maybe the routing of my oil pipes is a little different from yours and therefore
you wouldn't experience this phenomenon the same as I do. I can't swear that
it always behaves this way for me, but from now on I'm going to try to remember
to do the gurgling/burping about an hour after flight until I've gained enough
of a history.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=484345#484345
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