Minor Oil Leak - Opportunity for P.M.
Over the last couple of flights I've noticed a slight amount of oil was
being blown around the cowling and I've cleaned it up and let it leak
again to determine the source. My worry was that it was the
Lycoming 13792 Crankshaft Oil Seal (AEL13792 from ECI) on the front of
the engine. Having replaced one of those before on a different
plane, I wasn't looking forward to it. I prepped myself for the
repair and got a couple of seals, and also bought the PlioBond #20 (8
oz. can) that is required to get it back in and sealed. The only
thing I didn't have was the ST-383 tool that is recommended by this Procedure (Lyc S.I. 1324C)
After doing a bunch of leak snooping, I stumbled upon a spot that
seemed much more like the area that the oil was coming from. It
is a plug on the front of the engine for the Prop Governor idler shaft,
and is seen in this diagram as part number 6....Lycoming number 70455.
Below are a couple of photos of the plug before it came out. As
it turned out, the seal used was one of the copper crush type seals,
and my only other oil leak was from one of those. The 70455 p/n
is a more standard fiber gasket washer, so I replaced it with the one
in the Lyc parts manual. I also used Loctite
515 on the threads, as recommended by Bart at Aerosport. This stuff
was a little bit hard to come by, so if you ever need to do a task like
this, perhaps you want to prepare in advance by getting a tube when
you're visiting the right supplier. I got it from a local bearing
supply house for about $6....it's a non-hardening anaerobic sealant,
but from the sounds of it, Loctite 515 is not replaced by many other
types of chemicals. The closest one I could read about on the net
was Permatex #51813 Anaerobic
gasket maker. I didn't wan to risk it, so I got the real deal.
The entire job took just under 3 hours, to pull the cowl, the prop, the
ring gear, and then the plug. Then time to clean it all back up,
and put it all back together. Sure enough, the old seal wasn't
torqued super tight, and it obviously had loosened (not by turning out,
just by temperature cycling) over time, so it looks like it probably
was the culprit.
While everything was apart, I had recently purchased a new Gates 7375XL
alternator belt (11A0955) (13/32" x 38-1/8" (10mm x 967mm)) as a spare,
so having nearly 5 years on this engine now, I decided to throw that on
and use my original belt as the spare.
Additionally, I replaced the prop o-ring (Hartzell C-3317-228), and
kept the old o-ring as a tool kit spare.
So with that all done, it was a little bit of forced worth, that
accomplished a little preventative maintenance along the way. I was
thrilled to see that the area on the crankshaft just outside of the
front oil seal was almost completely dry, with no signs of an oil
leak. Those seals just make me nervous in that you have to
stretch the new seal over the prop hub, and I wasn't excited about that.