It seems to be the season for finding oil leaks.

At our completely uneventful annual (just finished two days ago) I asked my
shop to investigate a new leak that I had detected when I de-cowled the
engine for the inspection. All across the top of our 3-year-old, 500-hour
engine, down the seam where the case halves join together, right where the
push rods attach to the case, was a puddle of fresh, clean oil -- enough to
look like I had just spilled some while adding oil...

Trouble was, I HADN'T added any oil recently. With our new air/oil
separator, I no longer need to add oil between oil changes, so it had been
some 24 flight hours since I had last added oil.

With no obvious source of the leak, my mechanic thoroughly cleaned the
engine and resolved to fly it to see where the oil was coming from. The
flying weather wouldn't cooperate until today, but this morning we flew the
plane on its post-annual test flight, found a squawk or two, and returned to
the shop to fix these and check for the source of the leak.

The total flight time was only 0.7 hours, yet the top of the engine once
again looked like I had spilled oil while filling. It was right along the
case halves seam, so with no other apparent source my mechanic figured the
first place to start was to check the torque on the case bolts.

He reached for the first one, and we were both astounded when he was able to
tighten it -- by hand! One by one, all of the case nuts were found to be
very loose (although that was the only one that was hand-tight), and needed
to be re-torqued to 190 inch pounds of torque.

After tightening those, he checked the prop governor housing, and found
those bolts to be way loose, too. Essentially the whole top of the engine
was loose, and oil was leaking at the seam.

After re-torquing everything to spec, I test flew the plane for another 0.5
hours, and was happy to see everything bone dry once again.

Questions:

1. Is this something one should expect after 500 hours of shaking and
rattling? Do these bolts just plain loosen over time, going from hot to
cold hundreds of times?

2. Do you guys re-torque these bolts on a schedule?

3. Is this something your A&P checks at every annual? My guys were clearly
surprised to find these bolts so loose -- and they are the guys who rebuilt
the engine.

4. Are there any other bolts -- say, on the BOTTOM of the engine -- that I
should check for looseness? I looked but couldn't see any.

5. Should I apply LocTite to these bolts?

I suspect I'll be checking those bolts regularly from now on!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"