I had a very minor oil leak. You could see oil spots that
were so small, they were just pinprick in size on the
They ONLY were on the co-pilot side. Back then, I also had
oil inside my ring gear area, and dripping down hanging from the
starter and under my engine a bit.
Everything at the time pointed to being my crankshaft
I had replaced one years ago on my Sundowner, so I knew it
was a bit like the seal giving birth to a crankshaft flange
when you stretched it out. I replaced it, only to find that
I was getting less oil on the engine, the oil was still on my
windshield. It *seemed* to be a little less, but was still
there. I flew it for a while, after cleaning up
some oil a little, to see if it was just residual drops in
the cowl and engine that were making their way up, but it
kept coming. So over the winter I figured I screwed up the
job and did it AGAIN. The original seal was indeed
cracked all around the lips, and at 800 hours and 6 years
was getting older.
Well that didn't fix it either. I may have not done it perfectly
the first time around as there was a tiny bit of oil on my
inside of the ring gear, but it was not BAD. I kept poking
at it, tracking down everything I could to find the oil leak.
Eventually I resorted to adding UV dye to the oil. If you
this, keep it a SHORT TERM thing and don't do it unless
you plan to stick with the problem until you find it...within
a few days. Then change your oil. The reason is, if you
spread all that dye filled oil in your engine and it leaks
all over, pretty soon your whole engine will glow. So
resort to that when you need to, but keep it short term and once
you start diagnosing, don't stop and fly a lot until you
find it. For me, the dye helped some though.
I ended up getting to the point I had to degrease the entire
engine with Mineral Spirits solvents and then rinse off
with water and wipe the whole thing down with paper towels
so that I had a totally clean engine to start with. I
replaced an oil cooler hose, as part of the troubleshooting,
to ensure that the fitting wasn't leaking (I couldn't keep it
dry). I replaced my cylinder oil drain rubber tubes,
which definitely had hardened and a few were slightly
leaking. I removed and cleaned and sealed a couple sump
bolts and other things. Once I did all that, and after the
2nd crank seal, I no longer had any oil in my ring gear,
and my engine started to stay dry of any new oil leaks.
BUT, I still had oil on my windshield. If you look at the
photo below, you'll see the gap by the spinner
and the streaks of the oil flowing back. They'd trail
up to the windshield. I could NOT see the oil streaks
go INTO the air inlets, although on the copilot side
a few originated at the front upper part of the air inlet.
This turns out to be a pretty key signal.
Being at a loss of where the engine could be leaking, I called
to ask where oil could leak from the prop. I had to make
there wasn't any oil that could leak out. I had a
the engine was staying totally dry, if there was a prop oil leak
would get flung outward a little ways until the wind hit
Then, the DOWNWARD blade as it passes the cowl, leaves a small
between the blade and cowl. If oil were to fling off
would get thrown backwards and squeezed into that gap, and hit
cowl...running backwards along the top, initiating at the front
the cowl. I also didn't see any oil down the spinner gap,
oil appeard to be just bleeding out of the cowl itself.
pointed me to the prop...so I had to call Hartzell to
prop appeared dry of all oil though inside around the hub, so I
know how it could possiby be the prop. They said there
oil down the shaft where it enters the hub, only grease, so it
unlikely to be oil.