VAF Forums - Always Inspect the Oil Filter

I am not going to OshKosh this year, or to Mason City. The engine on
my -6 is on its way back from Bart LaLonde. The engine has 425 hours
on it since Bart overhauled it 3 1/2 years ago. It has run flawlessly
from day one. Here is the rest of the story.

During the Condition Inspection in early June, I changed the oil and
checked the oil sump screen. I found some metal flakes in the screen
and immediately cut open the oil filter. There I found about a half
teaspoon of metal. Some of it was ferrous and some looked like
copper. A few flakes looked like aluminum. See
http://eaa242.org/rvengine/rvengine.mht.

At that point I called Blackstone Labs, the folks who normally do my
oil analysis, and asked if they could analyze the metal. They
referred me to Howard Fenton in Tulsa. Howard's company is
SecondOilpinion. For a mere fifteen dollars Howard found that it was
mostly iron and copper with a little aluminum. He said the source of
the metal should be identified before further flight. He said it was
an unusual combination, but that it was probably coming from a
connecting rod bushing or a rocker arm bushing. After discussion with
him, Bart, and a local mechanic that I trust, I started removing
cylinders.

With all cylinders off, I could not identify anything unusual. More
talk with Howard, Bart, and local mechanic. Then I removed the
connecting rods and found a groove in one on the rod bearings.
Something, probably in the oil, had entered between the bearing and
the crank and cut the groove in the bearing. This could explain the
copper but not the iron. More talk. I had not found the source of
the metal.

At this point I bit the bullet, removed the engine and started
disassembly on the bench. When I split the case I found the center
main bearing badly chewed up. See
http://eaa242.org/rvengine/rvengine.mht. The bearing alignment pin
had been sheared off. This may have happened first or after the
bearing tried to turn in the crankcase. We will never know. In any
case, very soon the bearing would have turned and cut off oil flow to
that bearing and to two connecting rods. Then the engine would have
started to seize at the center main bearing and the connecting rod
bearings and bushings would have started to fail from lack of oil. It
would have been a race to see if a piston and/or a connecting rod
would depart the engine before it seized up. In any case, I would
have been looking at some unwelcome glider time.

After another discussion with Bart, I decided to send it back to him
for repair. I considered doing it myself since I have overhauled a
few engines. But I concluded that I would not have saved any time or
money (thanks to Bart). So I packed the parts in boxes, with the help
of some sympathetic friends, and shipped it to Bart.

Now, here I sit, feeling sorry for myself for missing Oshkosh and
Mason City, and for the unexpected expense of the repair. On the
positive side, I finally realized some benefit from careful
maintenance practices for the last quarter century that I have been
flying and maintaining my own aircraft. And more importantly, I did
not have to extract any tree limbs from any of my bodily orifices.

Finally, the moral of this story is: ALWAYS INSPECT THE OIL FILTER

Ken Harrill
RV-6, Columbia, SC