Observations about oil leaks

I bought a PA-24-260 with a verrry slow leak from the prop governor.
This has taught me some things about oil leaks.

1) Oil does not go in the obvious direction. Even after you take
into account the general airflow around the engine compartment and
baffling there are local variations that make it hard to see how
oil from point A can get to point B (without touching anything
in between!).

2) Oil can move verrrry slowly. When I got the plane the only external
sign of the leak was a fan on the pilot's side of the windshield (the
governor is at the left front above the oil cooler). A few weeks later
(and many flights a bit of oil would creep out from under the dipstick
access hatch. For a long time I thought that was a second leak, but
even after an oil change it was very dirty oil, and then I realized it
was the oil that didn't sneak out the front of the cowling and instead
slowly ran backwards on the underside until pressure forced it through
the gap (other clues included the oil door itself being clean). If you
wipe the bottom of the cowling off it goes away for a few hours.

3) One oil leak can come out multiple places (see (1) above) and at
different times (see (2) above) and look like multiple leaks.

4) A slow leak that is doing something like oiling the windshield
and irritating you may be mitigated by cleaning off the path from the
leak to the windshield. The oil that actually gets to the windshield
may be actually *leaked* on a different flight, and due to (2) moved
oh so slowly into position to get in your way. In the case of the
governor it seems to leak slowly onto the plate that the prop control
rotates and is blown off from there.

--
Ben Jackson

http://www.ben.com/

1) Oil does not go in the obvious direction.

Good post. And what you say is true with all fluids -- and all engines.

This summer I had some engine work done on my motorcycle, and immediately
afterward headed out for a 450 mile, three-day ride. (Dumb, dumb, DUMB.)

At our second rest stop, my 10 year old daughter asked what that "green
stuff " was under the motorcycle. Of course, it turned out to be coolant
(this on a Goldwing), and it was coming out at an alarming rate. Being in
the middle of B.F.E., I called Mary, had her hop on-line and find me the
closest Honda dealer -- which turned out to be in Dubuque.

The leak was coming out of the lower left, front portion of the engine. Due
to the extensive cowling on a Goldwing, I couldn't find the exact source of
the leak, and ended up adding water every 15 minutes until we got to the
shop.

After de-cowling the engine, the mechanic found the leak at a hose
connection -- on the TOP RIGHT portion of the engine! I would not have
found that leak in a hundred years -- it was traveling across the engine,
and down the opposite side, before dumping on the ground.

We had a similar problem with a minor leak on the right side of our engine.
It was coming out of the "gills" on the lower right side of the cowling,
just a small line of oil that would stream back after some (but not all)
flights.

The leak turned out to be coming from one of the valve covers on the TOP of
the engine.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

My best luck in tracing oil leaks on aircraft engines
has been to clean the engine with Stoddard solvent, dry
it with compressessed air, or otherwise let it dry.

Wait until night and pull the aircraft outside to where
it is nice and dark. Using a Black Light (uV lamp), inspect the
engine. Oil fluoresces, so note any oil residue not removed by the
cleaning, or which may have seeped out while the engine was being
dryed.

Run the engine at slightly above idle for one minute. Keep the
draft from the prop at a minimum while doing so as not
to spread the oil around much. Shut it down. Use the Black Light lamp
to check for new fluorescence.

Leaks that occur only while oil pressure is present should show up
during the first short run. If you dont see a leak, then run the
engine for a few more minutes, and look again. Oil leaks that are a
consequence of splash lubrication might require running the engine
longer or at higher rpms.

This method is particulary helpful in spotting leaks around
through-bolts, cyl base seals, crankshaft seal, accessories on their
mounting pads, etc.

MikeM

Great post,

This is the same way, we in the coating inspection industry, check for oil
on the surfaces to be painted or blasted if suspected. I found after more
than a few minutes of High intensity UV light on the surface, I needed to
wear UV glasses or the eyes burned.

Pat Thronson

"Jay Honeck" wrote in message

Being in
the middle of B.F.E., I called Mary, had her hop on-line and find me the
closest Honda dealer -- which turned out to be in Dubuque.

BFE?

Bum Firetruck Egypt

--

Thx, {|;-)

Victor J. (Jim) Osborne, Jr.



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