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Oil Leak

Cbull

Active Member
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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Front seal of the crank behind the prop based on location would be my guess. I hope you find it.
 
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.
 
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
 
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.
 
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.
 
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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the pic shows a VERY clean breather tube, even the inside of the tube. It is typically coated with an oily film. Any signs that oil is coming out of it? If not, the breather line could be blocked and that would force oil out of the crank seal. If the breather is blocked, excess pressure builds in the crankcase and the easiest way out then is the main seal.

YOu have an engine issue, not a 10 issue.

Larry
 
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the pic shows a VERY clean breather tube, even the inside of the tube. It is typically coated with an oily film. Any signs that oil is coming out of it? If not, the breather line could be blocked and that would force oil out of the crank seal. If the breather is blocked, excess pressure builds in the crankcase and the easiest way out then is the main seal.

YOu have an engine issue, not a 10 issue.

Larry

There is definitely oil coming out of the breather tube. That's actually the only place I see oil after I run up the engine. The discharge location of the tube seems questionable to me. It faces forward, well above the bottom of the fuselage, perhaps 2" or so. If there is turbulence there, it might be spreading everywhere. Maybe the crank seal is leaking in flight, but not while on the ground and running full static rpm.
 
How bout this . . . .
Forward facing crank case vent tube is somehow getting pressurized with the cooling exit air and creating increased crank pressure, enough now to go thru the forward crank seal.

Way to test; clamp flex tubing to end of vent tube with a turn BACK with the exit air. Leave it plenty long out the exit space. Then cowl back up to get the exit air direction and go flying. No oil, Im right. Oil continues, never mind. https://vansairforce.net/community/images/smilies/biggrin.gif

Just some mid-day armchair engineering.
Good luck.
 
How bout this . . . .
Forward facing crank case vent tube is somehow getting pressurized with the cooling exit air and creating increased crank pressure, enough now to go thru the forward crank seal.

Way to test; clamp flex tubing to end of vent tube with a turn BACK with the exit air. Leave it plenty long out the exit space. Then cowl back up to get the exit air direction and go flying. No oil, Im right. Oil continues, never mind. https://vansairforce.net/community/images/smilies/biggrin.gif

Just some mid-day armchair engineering.
Good luck.

That is exactly what I'm thinking. This afternoon I bought a 4" length of heater hose with a 90 in it. Clamped that on, it is now below the surface of the fuselage pointing straight down (still inside the lower cowl) I did a flight around the pattern and no oil. Checked the crank seal and it's dry. As soon as some storms pass I'm going up for a 30 min flight to see how it does.
 
That is exactly what I'm thinking. This afternoon I bought a 4" length of heater hose with a 90 in it. Clamped that on, it is now below the surface of the fuselage pointing straight down (still inside the lower cowl) I did a flight around the pattern and no oil. Checked the crank seal and it's dry. As soon as some storms pass I'm going up for a 30 min flight to see how it does.

Pretty sure the plans call for the breather tube to be facing forward. If that is the culprit, I’m sure we’d see many more issues with folks who followed the instructions. My tube is facing forward - I dont have any issues after 180 hours.
 
Oil leak possibly from valve cover

I had a leak on my 3 that I couldn’t figure out. It would have oil on the upper and side of the cowling and drip from the exhaust exit. It turned out the rubber seal on the valve cover was broken. If you have a rubber seal on the valve cover the surface and rubber seal needs to be oil free. If not when You tighten down the valve cover the rubber gasket squeezes out and breaks. If you use a cork gasket you put some oil on it so it doesn’t dry out over time. FYI, the rubber seal/gasket are $15 each compared to cork at about $2 each
 
Maybe o-ring on C/S prop mounting flange. Prop hub is more pressured in flight when course pitch is set, less so when ground running in fine pitch. Check if front face of flywheel is dry.

Another possibility might be dipstick is popping open, though unlikely
 
Check the elbows used for your oil cooler... if they are the blue anodized aluminum part, those are prone to hair line fractures and under pressure can spew a lot of oil.
 
One thing I have done in the past is to put fluorescent dye in the oil, run the engine. Move the aircraft out of the sun, use a black light to search for the leak. Truck shops I know of have the dye and if you are lucky may even be able to borrow their black light. Change the oil after you have finished sourcing the leak. The dye and a black light are also available to purchase from Snap-on Tools.
Ray
 
Maybe o-ring on C/S prop mounting flange. Prop hub is more pressured in flight when course pitch is set, less so when ground running in fine pitch. Check if front face of flywheel is dry.

I had a similar issue with my 7A Hartzell C/S with not quite as much oil as in your photos but a persistent leak. Ultimately it was solved by replacing the o-ring and polishing out a small imperfection that was preventing it seating for a good seal.
 
>The discharge location of the tube seems questionable to me. It faces forward, well above the bottom of the fuselage, perhaps 2" or so. If there is turbulence there, it might be spreading everywhere. Maybe the crank seal is leaking in flight, but not while on the ground and running full static rpm.

I would think that this is the problem.

The crankcase vent tube is supposed to be a "vent" that allows blow by gasses to escape the crankcase and this will prevent the inside of the engine to over pressurize and start blowing seals.

If the 45 degree bevel cut of the vent tube is pointed forward then the high speed air flow is smashing into the pipe and it becomes a ram air scoop that grabs as much air as possible and create a positive pressure.

If the 45 degree bevel cut of the vent tube is pointed aft then the then the high speed air flow first strikes the vertical forward wall of the pipe and this forces the air to swirl around the sides and as it passes the aft facing 45 degree bevel cut the inertia of the air passing by tries to draw air from the inside of the crankcase and this acts to scavenge (suck) the blow by gasses out of the crankcase.

Many crankcase tubes have an additional safety feature called a "whistle slot" cut into the tube and this cut is a simple cut line with the upward part of the tube pressed in and the slot opening is inside the engine cowling where it is warm...the idea being that if the moisture that is flowing out of the crankcase freezes at the vent tube opening and clogs up the opening with ice then the whistle slot will allow the engine to breath.

Just spin your existing vent tube 180 degrees and see if it helps. If so also add a whistle slot.
 
If the 45 degree bevel cut of the vent tube is pointed forward then the high speed air flow is smashing into the pipe and it becomes a ram air scoop that grabs as much air as possible and create a positive pressure.

If this is really the case, why would the plans not call this out? As I mentioned above, the plans show it facing forward. Wouldnt a ton of folks be having this issue? Mine faces forward and I dont have any oil leaking.
 
>The discharge location of the tube seems questionable to me. It faces forward, well above the bottom of the fuselage, perhaps 2" or so. If there is turbulence there, it might be spreading everywhere. Maybe the crank seal is leaking in flight, but not while on the ground and running full static rpm.

I would think that this is the problem.

The crankcase vent tube is supposed to be a "vent" that allows blow by gasses to escape the crankcase and this will prevent the inside of the engine to over pressurize and start blowing seals.

If the 45 degree bevel cut of the vent tube is pointed forward then the high speed air flow is smashing into the pipe and it becomes a ram air scoop that grabs as much air as possible and create a positive pressure.

If the 45 degree bevel cut of the vent tube is pointed aft then the then the high speed air flow first strikes the vertical forward wall of the pipe and this forces the air to swirl around the sides and as it passes the aft facing 45 degree bevel cut the inertia of the air passing by tries to draw air from the inside of the crankcase and this acts to scavenge (suck) the blow by gasses out of the crankcase.

Many crankcase tubes have an additional safety feature called a "whistle slot" cut into the tube and this cut is a simple cut line with the upward part of the tube pressed in and the slot opening is inside the engine cowling where it is warm...the idea being that if the moisture that is flowing out of the crankcase freezes at the vent tube opening and clogs up the opening with ice then the whistle slot will allow the engine to breath.

Just spin your existing vent tube 180 degrees and see if it helps. If so also add a whistle slot.

This is the path I'm heading down. I added a piece of hose to basically point the exit of the breather straight down. Still leaking. I ordered a new front crank seal and tool to change, a new prop o-ring, anti-splat oil separator and their vacuum package. I'm going to start with the antisplat items and go from there. I'll update as I proceed
 
Here’s my story. C182, started spewing oil in cruise. Couldn’t duplicate on the ground. Wondered if the crankcase was pressurizing in flight, so we looked up the TCM spec - I think it was 5” of water, max allowed (my memory may be off). So we hooked up some clear vinyl tubing to the breather, taped over the whistle slot, brought the tubing a safe distance back from the prop, used a T to attach a water manometer, the other end open. Started the engine, partner ran it up to 1500 rpm or so. Everything okay. I put my thumb partially over the open end of the tube, observed the water level start to rise. When it got to 1” (within allowed limits) oil suddenly came flying out from the vicinity of the oil pan-crankcase joint. Shut down and looked. All the screws attaching the oil pan were there, all were safety wired, just as the overhaul shop had put them in a year earlier. Then I did a double take. Every one of the starboard screws was safety wired backwards! And every one was now a half turn loose. I had never noticed. Cut the wire, tightened the screws, re-safetied. Leak gone. Probably a one in a million thing, but something else to check.
 
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Pretty sure the plans call for the breather tube to be facing forward. If that is the culprit, I’m sure we’d see many more issues with folks who followed the instructions. My tube is facing forward - I dont have any issues after 180 hours.

Think about the dynamic pressure (or lack thereof) on that hose. No way it causes a crank seal to fail. Now, if the breather was plugged, that might do it...

Adding math to the discussion... A 100 mph wind has about 50 lb/sf of force. Assuming that's the cowl exit velocity, convert 50 LB/FT^2 to LB/IN^2 and you get about 1/3 LB/IN^2.

I don't have a seal handy, but what's that seal's exposed surface area inside the crankcase? 3/8" x 9" = 3 3/8 IN^2?

Force x Area = 1/3 LB/IN^2 x 3 3/8 IN^2 = ~1 1/8 lbs.

So the pressure against the seal would be just over a pound if my estimates are reasonable. I don't think that would move a seal.
 
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This is the path I'm heading down. I added a piece of hose to basically point the exit of the breather straight down. Still leaking. I ordered a new front crank seal and tool to change, a new prop o-ring, anti-splat oil separator and their vacuum package. I'm going to start with the antisplat items and go from there. I'll update as I proceed

Some good guidance on installing the new seal out there...All I can add is to heat it up in boiling water or hot oil and have everything in place to install quick while it's pliable.

I replaced one this winter and broke the first one because I took too long before it got cold
 
Get the seal hot in boiling water also if you can park the plane facing into the sun and get the metal nice a hot. It will help.
 
Also put several raps/ layers of electrical tape around the prop flang to help prevent nicking the seal as you stretch it over
 
Well. Went ahead and replaced the main seal as well as the prop o-ring. Pretty sure it was the seal. After removing the prop and gaining access to the crank seal I discovered the seal was easily rotated with little pressure. That I'm pretty sure was the smoking gun. Thanks Lycoming. Not hard or expensive to replace, just took most of my Saturday to do it. The worst part is having to re-safety wire the **** prop bolts again! This time I'll put the safety wire through some tubing to protect the hub. I'm going to let the sealant cure for 24+ hours and reassemble everything. I'll clean the engine real good and hope to heck it stays oil free. I'l report back. Thanks for all the comments and responses.
 
Get the seal hot in boiling water also if you can park the plane facing into the sun and get the metal nice a hot. It will help.
Cory's in Austin - you only need to step outside to get things to close to boiling. :)

@Cory - do you think Lycoming just forgot the glue, or they didn't clean the surface well enough to ensure that the sealant adheres?
 
Cory's in Austin - you only need to step outside to get things to close to boiling. :)

@Cory - do you think Lycoming just forgot the glue, or they didn't clean the surface well enough to ensure that the sealant adheres?

I think they didn't use enough. Looks like there was just a small amount applied. The seal was rotating in the case, so perhaps some was removed that way. Either way the glue bond failed and here we are. Just happy to finally have a possible solution. I'll run it tomorrow after a nice long cure.

It is pretty warm here in the Austin area
 

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Hopefully all is well with your new seal. Just a word of caution about the seals. There is a .050 oversize seal that goes in a oversize hole in the case If they put a std. seal where a oversize one was susposed to go it would likely spin easily after it broke loose from the case. So if the replacement went into the case very easily or if it should pop out again that may be the issue and it may mean that you needed a oversize seal.
Good Luck,
Mahlon
 
Hopefully all is well with your new seal. Just a word of caution about the seals. There is a .050 oversize seal that goes in a oversize hole in the case If they put a std. seal where a oversize one was susposed to go it would likely spin easily after it broke loose from the case. So if the replacement went into the case very easily or if it should pop out again that may be the issue and it may mean that you needed a oversize seal.
Good Luck,
Mahlon

It's a brand new factory engine with 70 hours on it. Hopefully that's not the case. I suppose stranger things have happened
 
Oil Leak Fixed

Well, that did the job. Replaced the crank seal and 10 hours later all good. Thanks to everyone for the advice.
 
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