My 912ULS engine has done 250 hours since complete strip-down and rebuild after
I bought it from an acknowledged Rotax engine expert. The three others who share
the Europa with me are all happy with how sweetly it runs. The compressions
were measured very recently and are excellent (close to 200 psi). The oil
pressure
is good being in the vicinity of 4 bar. BUT....
Nine times out of ten the oil drains quickly (overnight) from the tank to a
level
below the flat on the dipstick. This wasn't always so and has become worse
over time. It used to take about a dozen compressions done quite slowly to push
the oil back into the tank, while these days it can often take 50 or more
compressions.
Why?
My supposition is that the oil escapes past the oil pump and the rate of escape
depends on the position of the pump lobes when at rest. So if the oil pressure
remains good in flight, what's changed? Perhaps the oil pressure relief valve
is sticking in some way?
Your experience and knowledge of likely causes would be gratefully received.
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