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O360 crank seal

wildduk

Member
We have an O360 with 300 hrs and can’t keep the crank seal from leaking. It stays seated, but will spin in place.
Compression is good. Oil burn is on high side for a low hr engine. 5 hrs/qt.

Any ideas.

Thx
 
What adhesive are you using and how are you cleaning the cavity before you glue the seal in place? It has to be microscopically clean of oil, or any adhesive will fail.

Paul
 
Oil seal

I never lube the seal/crank flange anymore because of the difficulty of cleaning off all of the lubricant before applying the adhesive. I use a clean dry plastic grocery bag over the flange which works great. Pliobond & Hylomar have both worked well for me as a adhesive.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
Service instruction SI1324C

I just changed the seal on a IO360. Followed Lycoming service letter SI1324C. Old seal was leaking on the outside due to no sealant left. It would spin by hand. I used the one-piece seal with the installer tool. The tension spring was a pita to reinstall. I got about 20 hours on it so far with no more leak. Ben
 
Oil seal

Be aware that there are oversize seals (outside diameter is larger) used in some engines. Information available from Lycoming.
 
The oversized seals are about 10X the price as the standard one, but it sure sounds like it was machined for the larger seal. Is the engine factory new with 300 hours or 300 SMOH?
 
300 SMOH. Would the case have any markings on it pointing it towards requiring the oversized seal? Or does the flange have to be measured?
 
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300 SMOH. Would the case have any markings on it pointing it towards requiring the oversized seal? Or does the flange have to be measured?

I speculate that only shops like Divco will make the seal cavity larger than std and only if a problem was found that required it. I doubt they would mark it as modified in any way. You will likely struggle to get a caliper or inside mic in there. It would seem that you may need to make a ring of a specific size for test fitting or find one of those old school inside calipers that look like a protractor.

Did you try test fitting the seal in the cavity before applying the adhesive? Was there some resistance when doing this or did it seem loose/sloppy when pushed in?

Larry
 
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Check to see that you have thrust bearing clearance . Holding the prop pull/push it in and out. There should be about .0002" movement iirc or there abouts. I had an engine were there was inadequate clearance and the only way to fix it was to send the case out to Divco. Mine was a new overhaul as well. With the proper clearance it never leaked again.

YMMV,
larry
 
The crank seal fits in snug, so probably not calling for the oversized seal.
Pliobond was used for the adhesive...
 
You have to put a thin film of grease on the crankshaft so the seal won't be torn out of place when you start the engine.

On a single piece seal, do the monkey shuffle to get the seal over the flange. Let it have considerable time (I use a day) to recover shape. Then, a really thin film of grease on the crankshaft - only where the seal will be. Then, seat the seal with pliobond. Another day to cure, and it should be good to go.

Can be a little tricky to get the grease on the shaft yet keep everything else clean for the pliobond to set up.

The seal should be fairly tight.
 
Check to see that you have thrust bearing clearance . Holding the prop pull/push it in and out. There should be about .0002" movement iirc or there abouts. I had an engine were there was inadequate clearance and the only way to fix it was to send the case out to Divco. Mine was a new overhaul as well. With the proper clearance it never leaked again.

YMMV,
larry

I can't recall the number, but the crank thrust clearance is in the neighborhood of .020" not .0002.
 
It stays seated, but will spin in place.

Any ideas.

Thx

I speculate that you are having a bonding issue. Both the seal and the C/C surface must be very clean. You should be cleaning aggressively with acetone or laquer thinner. Many rubber products come out of the mold with a substance on the surface that resists adhesives, Judicious cleaning is necessary. I use pliobond and have not had issues with it.

As mentioned above, never putting in this type of seal without a small amount of grease to lubricate for the initial rotations before the engine oil gets there.

Larry
 
Crank seal

Lycoming now recommends Dow 737 Neutral Cure Sealant. This is what I have used in the past and I have never had any problems.
 
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