Crankshaft expansion plug popped?

N79PT · #1 08-15-2009, 03:07 PM

The front expansion plug on the crankshaft justed popped loose a bit spilling some oil after a recent flight. Before I just coat the plug in it in high temp silicone and tap back into place what considerations are in order. Like, why did it happen, will it happen again, do I need to install a new part, etc., etc.

Particulars: O-360 A2F. It has been a FP setup since they put the engine in the original airplane (1963 Aero Commander Lark). Engine has been in my RV for 350 hours with a front crank seal pop-out after the first 50 hours of use. Re-installed the seal with no further problems. Oil pressure always runs about 85 psi.

Recent history: Replaced oil breather hoses. On climbout before the incident flight I noticed oil pressure indicating 90 psi and then back to the normal 85 in about 20 minutes. Pressure for the incident flight 85 psi.

Any advice would be appreciated. Thanks.

T6pilot · #2 08-15-2009, 03:39 PM

I'm not a Lycoming expert but it is highly recommended that you don't fly again until it get's installed properly. This is very serious. Recommend that you check the Lycoming site/a knowledgable A & P to get the correct procedure for installation. Sealant alone will not assure the plug will stay in place!!! Also, there may be an issue with the rear crankshaft plug. Maybe Mahlon will weigh in here? Fly safe.

P.S. I had a friend on his first flight of his RV 4 have this plug pop and he dumped 5 quarts of oil across his winshield before he got it on the ground. The plug was laying in the front of the crankshaft...

N79PT · #3 08-15-2009, 04:00 PM

I'm not going anywhere until it's fixed. The Welsh plug gets flattened a small bit on installation to cause the press fit to happen. The sealant is just that. I'm not certain you can reuse the old plug. I have reviewed VAF and the Matronic forumn for relevant insights. Just waiting for more RVers to weigh in. Thanks. --Greg

Mel · #4 08-15-2009, 06:20 PM

Do NOT reuse the old plug. It's a throwaway. Install a new plug properly. But first, be absolutely certain that the rear plug is either gone or pierced. I've never seen one come out that was installed properly.

N79PT · #5 08-15-2009, 07:29 PM

Thanks for the info Mel. I am very curious as why it would pop loose--it just cocked a little bit and that's when I noticed the oil. Any installation techniques you'd like to share to make sure I've got it right?

DanH · #6 08-15-2009, 09:44 PM

Need MEK, a new plug, some Loctite 515, and a brass or aluminum drift, flat faced with a diameter a little less than the crank bore.

Clean the crank bore carefully with MEK, meaning no traces of old sealant or oil.

Inspect as Mel said......make sure the rear plug has a hole.

Place a tiny bead of 515 into the recess of the shoulder in the crank bore where the plug will seat.

Insert the plug against the shoulder. The dome side faces out. Use the drift and a big hammer to set the plug. I've never seen any written guidance as to how much to drive it. The few I've done were driven until about 3/4 of the diameter was flattened. Anybody know an official spec?

David-aviator · #7 08-16-2009, 07:59 AM

Quote:

Originally Posted by DanH

.... I've never seen any written guidance as to how much to drive it. The few I've done were driven until about 3/4 of the diameter was flattened. Anybody know an official spec?

I don't think there is a spec. The overhaul manual has no instructions with regard to flattening the front expansion plug, it just says be sure fits firmly against the shoulder provided for it. (par 7-62) The aft plug, which is quite different and installed when a CS prop is used, is set with "several sharp hammer blows on the drift". (par 7-63)

Have you installed the aft plug? If so, how difficult is it to get the plug past the propeller oil tube and into its seat?

DanH · #8 08-16-2009, 10:03 AM

Quote:

Originally Posted by David-aviator

I don't think there is a spec. The overhaul manual has no instructions with regard to flattening the front expansion plug....

Yeah, just an official Lycoming tool number for the drift.

Quote:

Have you installed the aft plug?

Nope.

N79PT · #9 08-16-2009, 01:35 PM

Quote:

The few I've done were driven until about 3/4 of the diameter was flattened.

The plug on my engine was only flattened slightly, perhaps 1/4 of the diameter. Perhaps that's the indication of the problem. I will definitely make sure the there is no obstruction in the rear part of the crank.

T6pilot · #10 08-16-2009, 06:48 PM

Quote:

Originally Posted by David-aviator

I don't think there is a spec. The overhaul manual has no instructions with regard to flattening the front expansion plug, it just says be sure fits firmly against the shoulder provided for it. (par 7-62) The aft plug, which is quite different and installed when a CS prop is used, is set with "several sharp hammer blows on the drift". (par 7-63)

Have you installed the aft plug? If so, how difficult is it to get the plug past the propeller oil tube and into its seat?

I've installed a rear plug. It goes around the transfer tube very easily since the transfer tube is offset. I just installed a c/s prop conversion from fix pitch and it's quite a project. It was a challenge to get the old rear plug removed since it was punctured for fix pitch, but I did it...