oil leak; prop seal opinion wanted.

[rbridges]

I've had the crankshaft seal replaced a few times on my mooney (lycoming O360). It's much improved, but I'm still getting small amounts. I was looking at some pics I took at the last repair. I don't have much personal experience, so I was wondering what you thought of the crankshaft. Are these scratches pretty typical? Anything that could cause a leak with the O-ring seal? Sorry, these are the best pics I have.

 

[Salty]

How long has it been since that crank has been overhauled?

 

[rbridges]

~1100 hrs since zephyrbhills overhaul in '98.

 

[charlie]

Scratches on the pilot portion of the shaft come from working the prop to get it on or off. This will not cause an oil leak. The leak could be the seal... Charlie Melot X Zephyr owner.

 

[Clip4]

I've had the crankshaft seal replaced a few times on my mooney (lycoming O360). It's much improved, but I'm still getting small amounts. I was looking at some pics I took at the last repair. I don't have much personal experience, so I was wondering what you thought of the crankshaft. Are these scratches pretty typical? Anything that could cause a leak with the O-ring seal? Sorry, these are the best pics I have.

View attachment 63962 View attachment 63963

You could fly the plane to a prop shop and let them give you an opinion if the leak is from the prop or the crank seal.

 

[Tom-D]

You could fly the plane to a prop shop and let them give you an opinion if the leak is from the prop or the crank seal.

Why would a prop shop know better about an engine seal?

 

[Clip4]

Why would a prop shop know better about an engine seal?

Maybe the mechanic is fixing the wrong issue.

 

[George Mohr]

Hey interesting note. All prop seals are not the same. My engine had the seal flange bored 50 over at some point in its life. Took two failed seal replacements to discover this fact and get the right seal in there.

 

[rbridges]

Hey interesting note. All prop seals are not the same. My engine had the seal flange bored 50 over at some point in its life. Took two failed seal replacements to discover this fact and get the right seal in there.

I wondered about that. How bad were your leaks? The last IA tries to measure but he couldn't get his calipers on the crank by the seal. The arms to his gauge were too short . I looked in the logs and couldn't find any mention of an oversized crank .

 

[Salty]

Max allowed under for a lycoming 0-360 main crank I believe is .010”. I doubt the standard rubber seal would leak with such a small difference, but I’m no expert.

I would think the location of the oil would make it obvious if it was the crank seal vs the hub o-ring.

 

[George Mohr]

I wondered about that. How bad were your leaks? The last IA tries to measure but he couldn't get his calipers on the crank by the seal. The arms to his gauge were too short . I looked in the logs and couldn't find any mention of an oversized crank .

It was replaced twice before we figured it out. The first time the seal lasted for 1.5 years. The second one lasted 9 months. Then we discovered it was 50 thousandths under. The first time the leak was slight, but annoying. The second time it started light, then got serious very quickly.

Also, I don't think the issue was the crank O.D. I think it was the crankcase flange I.D.

 

[rbridges]

Max allowed under for a lycoming 0-360 main crank I believe is .010”. I doubt the standard rubber seal would leak with such a small difference, but I’m no expert.

I would think the location of the oil would make it obvious if it was the crank seal vs the hub o-ring.

This is an older picture. The leak is much less than this, but it's the same general location. The oil pools inside the hub to the flywheel. It seems like there may be streaks coming from the forward part of the hub like it may be coming from the prop hub, but I'm really not sure how airflow would affect how the oil moves around.

 

[Salty]

View attachment 64042

This is an older picture. The leak is much less than this, but it's the same general location. The oil pools inside the hub to the flywheel. It seems like there may be streaks coming from the forward part of the hub like it may be coming from the prop hub, but I'm really not sure how airflow would affect how the oil moves around.

I would check for oil running down the bottom of the case from the seal after running the engine.

 

[rbridges]

I would check for oil running down the bottom of the case from the seal after running the engine.

If it is, it's so little that it's hard to tell. I can get a fine mist on the case in that area, but no runs. The only noticeable accumulation is in the flywheel.

I do remember looking at the old logs, and they used the same crankshaft seal that I inserted, so it wasn't oversized.

Anyway, I do appreciate everyone's input.

 

[Checkout_my_Six]

along the lines of "why".....what causes the seal to "leak"?

wrong seal dimensions....over/under sized.
pressurized crank case - leaky piston seals - broken rings.....???? just a thought.

 

[Salty]

If it is, it's so little that it's hard to tell. I can get a fine mist on the case in that area, but no runs. The only noticeable accumulation is in the flywheel.

I do remember looking at the old logs, and they used the same crankshaft seal that I inserted, so it wasn't oversized.

Anyway, I do appreciate everyone's input.

Hopefully someone with more experience will chime in, but it sounds to me like it’s the oring rather than the seal. It’s not that hard to swap it out, maybe give it a shot and make sure all the surfaces are very clean. The hardest part of the job is the safety wiring.

 

[Raymo]

Which sealant is being used on the outer diameter of the crank seal? I believe Lycoming recently updated the recommended sealant and every mechanic will have a favorite.

 

[charlie]

I have only encountered maybe 4 engines that had oversize crankshaft seals in my career. It is the boss in the crankcase that is bored to P.050 requiring an oversize seal. I saw one instance of a leaky seal that finally got resolved with the fifth seal. It lasted a long time. There are a bunch of tricks around such as creating a crosshatch on the shaft to seat the seal. Got to use the right glue and best let it sit for a day. As said here a buggered prop O ring will leak just like a bad crankcase seal. Changing seal vendors sometimes works. There's OEM and Superior to chooses from. ECI used to sell seals too. We pulled the cowl off a Comanche engine and found the crankshaft seal hanging on the shaft. It was dry as the proverbial popcorn fart. Saw a Lycoming that had a distortion of the slinger creating an oil pump if sorts. A Pitts engine owned by a friend was consuming seals. Lycoming told the owner he ought to tear it down. We took it apart to find the crankshaft was seriously cracked. Charlie Melot

 

[c5guy]

Interesting discussion. I’m having a problem with a small oil leak on my brand new factory reman O-360A1F6 on my Cardinal. I’ts been leaking since the first flight (I noticed some speckling on my windscreen). After I put about 5 hours on the new engine, I took it back to my mechanic. He replaced the O-ring yesterday after thoroughly cleaning the groove and taking care the O ring was seated properly. He ran the engine on the ground and cycled the prop, and it’s still leaking. He is reluctant to pull the prop again without a plan. I’ll suggest a seal from another vendor.

 

[rbridges]

Took this today through an opening in the spinner cover. I'm a layman, but isn't this consistent with the prop o-ring leaking? I don't see how a crank seal could cause it to leak here.

 

[c5guy]

Took this today through an opening in the spinner cover. I'm a layman, but isn't this consistent with the prop o-ring leaking? I don't see how a crank seal could cause it to leak here.

That is EXACTLY what the leak on my Cardinal looked like. The fix was to smooth the crank shaft to remove some small scratches and replace the O-ring (again). Make sure you thoroughly clean the front of the engine of residual oil afterwards - I thought I got it all but some residual oil still found its way out onto my cowling and windscreen. I thought it was still leaking. Pulling the spinner and inspecting the ring gear support (like the one in your photo) showed no more oil “streams”, which confirmed we fixed the problem and what I was seeing was residual.

 

[rbridges]

That is EXACTLY what the leak on my Cardinal looked like. The fix was to smooth the crank shaft to remove some small scratches and replace the O-ring (again). Make sure you thoroughly clean the front of the engine of residual oil afterwards - I thought I got it all but some residual oil still found its way out onto my cowling and windscreen. I thought it was still leaking. Pulling the spinner and inspecting the ring gear support (like the one in your photo) showed no more oil “streams”, which confirmed we fixed the problem and what I was seeing was residual.

Thank you!

 

[Cherokee Lover]

Rob...did you ever get your leak fixed? I figured out how to resolve it. Give me a call.