Don't be too quick to make assumptions about where leaking oil
goes under a cowl. The airflow under the cowl is faster and in more
directions than you might think. It carries oil into the most unexpected
places. Sometimes the source is obvious and sometimes not. As always
in this endeavor, there are very few absolute rules.
----- Original Message -----
Sent: Wednesday, February 09, 2005 1:19
PM
Subject: [FlyRotary] Oil leak
Hi
Guys,
I've
been chasing an oil leak for a while now. It only happens when the engine is
running. When I get back from a 20 minute flight the cowl has oil streaks down
the outside, everything under the cowl has an oil film on it, and the
turbo is seriously smokin'. I could probably make a similar mess by
spraying about 1/2 cup of oil at the cowl and engine.
Today I took the plane up and down the runway a couple of times and did
a couple of runups with the cowl off. I seem to be a little down on power -
(3950 instead of 4050 on static). When I got back the mount plate below the
turbo had fresh oil on it and I could see air bubbling through this oil at the
joint of the mount plate and the engine, just by the turbo. See attached
picture with arrow. In fact the entire join between the engine and the plate
on the right (turbo) side seems wet with oil and there's another pool at the
front which I don't think migrated from the back.
I
get the feeling that this "bubbling" might become a fine jet of oil which
points directly at the turbo when the engine's running, otherwise I don't
see how oil could get up into the turbo housing and smoke like it does.
I'm trying to understand why there might be pressure here. The breather
is definitely not blocked, and in fact, on this particular run, I'd even left
the dipstick out. Could the bubbling air be a compression leak from the join
between the rotor hosing and the backplate? My oil level is maybe 1/4 -
1/2 inch below the level of the mount plate and the plane was on a slight
grade making the back lower. The bubbling stopped after a few minutes and did
not return when we turned the prop.
I'm
resigned to pulling the lower cowl, sump and sump plate and redoing the RTV
join (again), but I'm wondering - should there be pressure here? Is there some
other problem causing this. Am I overfull with oil? Could the turbo oil
return be "landing" on the mount plate, then running back along the join? I'm
planning a compression test next time I go down to the hangar.
Any
other thoughts or suggestions?
Regards,
John
(13.9 hrs and holding)
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