HOLY SHIT. THAT COULD HAVE KILLED ME.

[Brian Scranton]

On our 14 hour flight home to CO from NJ I noticed some shimmering/glistening on the cowl just an inch or two aft of the prop...I thought to myself, "Hmmm, I must have a little leak somewhere." 

So I bring her in to get the wastegate fixed (cuz it broke and I lost the turbo at 17K a few weeks ago) and mention the shimmer to my A&P and point to a bit of streaking on the cowl. We pull the top cowl and he starts to laugh and says, "I can't believe you didn't have oil all over your windshield." And points to the prop seal that had worked its way completely out of its home. JESUS. 

Not only did I learn how to remove a turbo today but I also learned how to remove a prop!     

[peevee]

Yikes. Glad it all worked out.

[Yetti]

Prop seal or main crankshaft seal?

[Brian Scranton]

The seal that goes into the engine block where the prop mounts--aka, the prop seal--at least that's what they were calling it. Yikes is right. 

[peevee]

2 hours ago, Brian Scranton said:

Yikes is right. 

I need to be better at listening when the plane is trying to tell me something.

[Guest]

2 hours ago, Yetti said:

Prop seal or main crankshaft seal?

Same thing in most circles.

Clarence

[Yetti]

It's held in with really sticky glue.

 

[carusoam]

Great Pirep, Brian.

Get the seal replaced, post a pic of the old one if you can...

You should be good to go, trouble free, for some time! 

Best regards,

-a-

[Brian Scranton]

Interestingly, the prop seal was devoid of any sign that it had that sticky glue on it. Worked its way totally out. A local CFII who also is an A&P was in the shop and said the same thing just happened to him last week. The seal was sitting up on the fourth cylinder. 

[Yetti]

It probably had been spinning for awhile before it worked itself out.   It may have oversized the hole. They make oversized seals.   2 professionals have worked on my plane.  The second one caught the seal was spinning.  Taking all safety into mind.   You can test yourself.  Put a finger on it, move the prop see if it moves.   I think my engine was warm when we did this test.  Professionals are there for you.   I don't think much pressurized oil hits the seal so it is not as critical as some other places oil can exit the engine while in flight.

[Vance Harral]

2 hours ago, Brian Scranton said:

A local CFII who also is an A&P was in the shop and said the same thing just happened to him last week. The seal was sitting up on the fourth cylinder. 

My impression is the failure isn't all that uncommon.  We've had it happen twice in 14 years of ownership.  Little more oil than usual, discover compromised main seal when pulling the cowl and feeling behind the prop.

I know it's scary to think all the oil could drain out in flight.  But the prop flange end of the crankshaft exits at the top of the case.  Assuming you're not flying aerobatics, the only oil that will blow out there is little droplets from splash lubrication.  Even if the seal completely departs, I don't think it's likely to be an OMG-I-coulda-died failure.  It's certainly not the same as losing your oil drain plug, or blowing a hole out the bottom of the case with a thrown rod.

I'm not trying to water down your concern, though, just explaining why the main seal mechanism likely isn't more robust to start with.

[thinwing]

22 hours ago, Brian Scranton said:

On our 14 hour flight home to CO from NJ I noticed some shimmering/glistening on the cowl just an inch or two aft of the prop...I thought to myself, "Hmmm, I must have a little leak somewhere." 

So I bring her in to get the wastegate fixed (cuz it broke and I lost the turbo at 17K a few weeks ago) and mention the shimmer to my A&P and point to a bit of streaking on the cowl. We pull the top cowl and he starts to laugh and says, "I can't believe you didn't have oil all over your windshield." And points to the prop seal that had worked its way completely out of its home. JESUS. 

Not only did I learn how to remove a turbo today but I also learned how to remove a prop!     

Maybe that engine is talking to you...

[Brian Scranton]

I think I would have rather crashed than safety wire this damn prop (joking of course). Holy hell--what a pain in the ass!!!! 

 

 

[Jim F]

Hi Brian,

Make sure your crankcase breather is clear. If it is kinked, plugged or restricted then the crankcase pressure builds up from blow by it can pop the crank seal out.  

Jim

[cliffy]

Why did the prop have to be removed?

If the seal recess hole is not worn oversize then the split seal type can be used to replace the old seal without removing the prop. If the hole IS worn oversize then the engine must be completely torn down and the hole machined for the .050 oversize seal. 

Seems like a lot of extra work was done when it didn't have to be. 

Here's the Lycoming SI     https://www.lycoming.com/sites/default/files/Crankshaft Oil Seals.pdf

Also, as mentioned, WHY did it come out? If it was a constricted breather line it could have developed crankcase pressure and blown it out. You need to check the breather hose although if you had a blocked breather you would have blown out more oil around the crankshaft.

How old is the seal? It could just be old and worked loose because of no glue. 

Never having flown a TN Mooney (but LOTS of other turbo'd airplanes), is flying with an inop turbo an approved operation in one? 

[Yetti]

16 hours ago, Brian Scranton said:

I think I would have rather crashed than safety wire this damn prop (joking of course). Holy hell--what a pain in the ass!!!! 

 

 

I kind of likened it to the "test"/exam/making the grade/gaining trust/quest  of the Professional.   Did not wimper when he said do it again.   "Yes Sir"

[Guest]

2 hours ago, cliffy said:

Why did the prop have to be removed?

If the seal recess hole is not worn oversize then the split seal type can be used to replace the old seal without removing the prop. If the hole IS worn oversize then the engine must be completely torn down and the hole machined for the .050 oversize seal. 

Seems like a lot of extra work was done when it didn't have to be. 

Here's the Lycoming SI     https://www.lycoming.com/sites/default/files/Crankshaft Oil Seals.pdf

Also, as mentioned, WHY did it come out? If it was a constricted breather line it could have developed crankcase pressure and blown it out. You need to check the breather hose although if you had a blocked breather you would have blown out more oil around the crankshaft.

How old is the seal? It could just be old and worked loose because of no glue. 

Never having flown a TN Mooney (but LOTS of other turbo'd airplanes), is flying with an inop turbo an approved operation in one? 

It would be quite a trick to replace the seal on a Lycoming with the starter ring gear and propeller in place.

Clarence

[cliffy]

You know, you might be correct. I have to go look at mine again because I did use a split one when I did mine 

Maybe it was too early in the morning for me to think :-) :-) and not be looking at the plane. 

DOOOH!