europa@pstewart.f2s.com wrote:
> we have just run the engine up (914) for the third time. After about 5 min
> there
> was oil dripping from the right hand airbox drain and the air filter is soaked
> in oil. There is no apparent leak from anywhere else. The oil tank has never
> been over filled. The engine does not appear to be burning oil. It appears
> that
> it has been drawn up into the airbox from the turbo - but why the air filter
> soaked in oil? The first couple of engine runs (couple of months ago) there
> was
> no evidence of oil leaking anywhere. Any thoughts?
Looks like a turbo problem. Oil leaking via the bearing into the inlet.
The air stream takes small oil bubbles up into the airbox, but the
majority of the oil will probably dribble into the air filter.
Could there be a problem with the turbo oil return line? Should go to
the auxiliary oilpump, and from there to the oil tank. If you disconnect
it at the oil tank and run the engine, oil should be dripping out of
this line. If no oil shows up, then you have found the problem.
Wait a minute! You ran the engine a couple of months ago for the last time?
Maybe the oil flowed back, and sucked some air in the turbo oil return
pump. Once there is air in this pump, it won't pump oil anymore, and the
oil will need to find another way out. Most likely than it will overflow
into the inlet air channel.
You can also have air in the oil system if you (or someone else) turned
the propeller the wrong way. Never tested it myself, but I've heard that
just a quarter of a turn in the wrong direction can allow air to get
into the oil system.
Do the test with the oil return line, and if it doesn't produce oil, you
will have to prime the oil system. This works great by pressurizing the
oil tank and turning the propeller by hand until oil comes out of the
oil return line.
--
Frans Veldman
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