found oil on the floor, grounded

[snopercod]

I've always used Pliobond and so does the maintenance shop at my airport. But I guess you know that Lycoming recommends Dow 737 Neutral Cure Sealant. It's in Lycoming Service Instruction No. 1324C.

I'm not going to re-read the entire thread, but are you absolutely sure it's the crankshaft oil seal? The reason I'm asking is that I hunted for months to find the leak on mine and changed the seal when the real leak turned out to be at the rocker cover gasket on the #4 cylinder. I had over-torqued the R.E.A.L. red RTV gasket. The only way I found it was to add that fluorescent dye to the oil and use a UV light in a darkened hanger. On my long hunt for the leak, I even taped up a butcher paper ring around the crankshaft in front of the oil seal and went flying. I figured that would prove one way or the other whether the oil was coming from the crankshaft seal. It seemed like a good idea, but results were inconclusive since oil was flying all over inside the cowling. Good luck.

[Steve Melton]

I used a borescope and could see the oil trail from the bottom of the seal so I'm sure that's the source. I may try the DC 737 instead of the pliobond. I thought we had a done a good job on the replacement so I'm not sure of the root cause of the failure. I added side holes to the breather tube to ensure no over pressure could exist. It's a goofy design to rely on glue on this big seal to keep the oil inside the engine.

[rwtalbot]

Our local engine shop prefers 5 min/high strength epoxy for experimental. They say it virtually eliminates this issue.

[snopercod]

Originally Posted by Steve Melton

I used a borescope and could see the oil trail from the bottom of the seal so I'm sure that's the source.

Sorry. I didn't mean to patronize. Was it possible to tell whether the oil was coming from around the crankshaft or from the seal-to-case area?

When I changed my seal, I did some light polishing of the crankshaft with 600 grit wet-or-dry. Interestingly, Continental SB M76-4 advises using emery cloth to scratch a "helix" on the crankshaft under where the seal will be. I assume that is to sling any oil back toward the engine.

[Steve Melton]

unable. when I get the prop off (again) it will be a better view.

[9GT]

Did you check the bore size of the seal flange when you last replaced the seal? Lycoming makes a .050" oversize seal for worn bores. https://www.lycoming.com/content/ser...ction-no-1324c As a side note and previously mentioned, Lycoming recommends the Dow 737 natural cure sealant. Do you have access crankcase pressure working the seal loose? I read somewhere that Lycoming used a bolt on retainer ring to hold the seal in on some of their engines. I had a co-worker that was also a pilot and owned a Beech Super Musketeer. The oil seal blew out on him during climb out and he was very fortunate to get the plane back on the runway with the windscreen covered in oil. Fearful that would happen to me, when I replaced my leaking crankshaft oil seal, I made a .062 aluminum split ring that fit the front of the case in front of the crankshaft seal flange. and Pro-Sealed it in place. I had a lot of crankcase blow-by from a couple marginal cylinders. About 50 hours later I decided to replace the cylinders with new power assemblies, but the retainer ring gave me piece of mind.

[snopercod]

Originally Posted by 9GT

I read somewhere that Lycoming used a bolt on retainer ring to hold the seal in on some of their engines.

Yes, my O-290-D2 with the O-320 crankshaft has one. It's split in two halves and held on with four #8(?) screws. This photo was of my attempt to confirm that the leak was truly coming from the seal. That paper around the crankshaft is a sandwich of butcher paper on the inside and wax paper on the outside. As I recall, after flying the plane with the butcher paper, it was was mostly oil-free but I ignored that evidence and changed the seal anyway (Story of my life...sigh):

[lr172]

Originally Posted by Steve Melton

I used a borescope and could see the oil trail from the bottom of the seal so I'm sure that's the source. I may try the DC 737 instead of the pliobond. I thought we had a done a good job on the replacement so I'm not sure of the root cause of the failure. I added side holes to the breather tube to ensure no over pressure could exist. It's a goofy design to rely on glue on this big seal to keep the oil inside the engine.

Were you able to confirm that the oil was leaking from the OD of the seal, from a compromised glue joint, and not the ID? The crank can wear at the seal location and cause leaking. I would also check the case bore to be sure that it was not machined to a larger bore at some time.

Also, did your case have a small channel machined in the bore? Mine did (O-320) and the seal had a ridge that helped to lock it in the bore.

Larry

[Steve Melton]

history: I replaced the original seal 100 hrs ago (460 hrs total time) because it became totally unseated and was resting on the crankshaft. It was replaced with a similar seal using Pilobond adhesive rather than the original white RTV. Yesterday upon oil change I found it was leaking. The Pilobond is secure and the seal is seated and the leak is between the crank and the seal. There is a black color to the leaking oil but my internal oil is clean so I can only presume the seal is wearing but not sure why. question is: how to remove the seal for replacement?

[C-FAH Q]

Take a cotter pin removal tool, poke it into the seal and pull. Then cut seal with a knife. Make sure to replace the spring with the new one that comes with it. Ensure the spring is fully seated on back of seal before inserting.