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  #1  
Old 08-01-2021, 07:55 PM
Cbull's Avatar
Cbull Cbull is offline
 
Join Date: Feb 2013
Location: austin, TX
Posts: 74
Default Oil Leak

Did a search for "oil leak" in RV-10 and returned nothing usable. Sorry if this has been hashed out before

I'm at a loss. I can't find an oil leak. New XIO-540-D4A5 with Hartzel Scimitar 3 blade prop, 60 hours on engine.

Noticed oil leak a week ago, but have noticed evidence of it on the top of the cowl for a long time. Small streaks going up cowl and onto the windscreen. Once it started pooling on my hangar floor it got my attention.

Decowled, washed down really well. Completely clean. Full static run up, with prop cycles in between. Let the oil get hot, 130. Found a few drips, but suspect they were from heating up the engine and the oil came out of places I couldn't clean well. Cleaned again, ran it again, no leaks can be found. Performed oil change, added 8 qts (she seems to like 6).

Flew today for an hour and again, oil dripping from cowl. Also need to mention oil is coming out of the two front intakes and flowing down front of cowling. Did the whole de cowl, clean, run up, clean again and on final run up, no leaks. Felt as much as the crank seal as I could get to, it was dry.

It seems to be wettest around front of engine, below all baffling. Dry as a bone on top. Oil pools on top of the air box. Bottom of engine completely coated. Lower cowl soaked as well.

Theories/guesses

#1 The breather tube faces forward, kinda odd. I guess the idea is to not face it rearward and create a suction. Is it possible ram air is coming from the bottom cowl where gear is and producing enough pressure in the case to make the crank seal leak? The slot around my front gear may be a little larger than normal. Because of the 3 blade prop. I do have a removable section for lowering cowl. I'd say 3" of clearance from front of gear to cowl.

#2 Is oil dropping out of breather tube, hitting cowl and weeping forward due to some weird turbulence inside the cowl. Again, there is oil coming out of the air intakes and flowing down front of cowl.

#3 on the last run there where small streaks on the back of the prop blades. Very small amount, may have been residual. Prop leaking...???
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  #2  
Old 08-01-2021, 09:47 PM
RandyAB RandyAB is offline
 
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Default

Front seal of the crank behind the prop based on location would be my guess. I hope you find it.
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  #3  
Old 08-01-2021, 09:58 PM
PilotjohnS PilotjohnS is offline
 
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Default breather

Is the breather not working and the crankcase building up pressure? Dont expect the forward facing breather alone to build up sufficient pressure. Seems like a lot of oil, but what do I know, I am still in the building stage.
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  #4  
Old 08-02-2021, 12:56 AM
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Quote:
Originally Posted by RandyAB View Post
Front seal of the crank behind the prop based on location would be my guess. I hope you find it.
Same idea. And it's fun to replace I've read. If it were the breather, you'd probably see a few more hints back there. Slide your finger on the inside of the ring gear and you'll know then if it's the nose seal.

Lycoming has some hints here:

https://www.lycoming.com/content/how...nose-seal-leak
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  #5  
Old 08-02-2021, 12:58 AM
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Quote:
Originally Posted by PilotjohnS View Post
... Seems like a lot of oil, ...
I too think it is a lot of oil.
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  #6  
Old 08-02-2021, 06:55 AM
lr172 lr172 is offline
 
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Looks like a LOT of oil for one flight. My first guess would also be the crank seal. With that much oil leaking, You shouldn't have a problem seeing the leak on the ground with the cowl off. Just need to deal with spinning prop.

Clean well, point your go pro at the bottom front half of engine and start. Should see leak point in a couple minutes.

Larry
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  #7  
Old 08-02-2021, 08:33 AM
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Cbull Cbull is offline
 
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Quote:
Originally Posted by rv8ch View Post
Same idea. And it's fun to replace I've read. If it were the breather, you'd probably see a few more hints back there. Slide your finger on the inside of the ring gear and you'll know then if it's the nose seal.

Lycoming has some hints here:

https://www.lycoming.com/content/how...nose-seal-leak
I did that. I can get to about 1/2 of the seal behind the ring gear and it is dry.
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  #8  
Old 08-02-2021, 08:37 AM
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Cbull Cbull is offline
 
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Quote:
Originally Posted by lr172 View Post
Looks like a LOT of oil for one flight. My first guess would also be the crank seal. With that much oil leaking, You shouldn't have a problem seeing the leak on the ground with the cowl off. Just need to deal with spinning prop.

Clean well, point your go pro at the bottom front half of engine and start. Should see leak point in a couple minutes.

Larry
I ran it several times on the ground and zero leaks. Ran it up to 2650 RPM for about 30 seconds and 2000 for several minutes. Total run up time around 5 minutes, no leaks. Did this twice. I had 100 psi oil pressure on takeoff. After the oil got really warm it would be around 96 psi. I adjusted the oil pressure so that I now get 87 psi max at full throttle. Still leaking in flight, but not on the ground.
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  #9  
Old 08-02-2021, 09:19 AM
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Mike S Mike S is offline
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Default

Prop governor might be a candidate.

Have you pulled the spinner to see if there is any oil inside it?

Moved this to the engine forum.
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  #10  
Old 08-02-2021, 09:32 AM
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Quote:
Originally Posted by Mike S View Post
Prop governor might be a candidate.

Have you pulled the spinner to see if there is any oil inside it?

Moved this to the engine forum.
I did check the prop governor, dry. There is a small amount of oil splashed on the back of all the blades. That occurred will running engine with the cowl off. The prop hub itself seems to be dry though.

Thought this might be an RV-10 specific issue and was hoping other fellow -10 guys may have had the same issue. Thanks Mike
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Last edited by Cbull : 08-02-2021 at 09:35 AM.
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