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oil leak on top of engine?

A5555

Well Known Member
I don't understand this one. It's not the fwd crank seal. Has anyone had anything similar? thx, Steve

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fwd crank seal area is clean
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splatter on the cowl
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Yep.

I have had a similar leak. I was getting some leakage from one of the safety-wired bolts in the photo, then later I had a leak from the bolt hole at the top of the case where the engine hoist bracket is installed. To fix that one my A&P friend, Mike Cingari, recommended removing the bolt, cleaning the hole out and using green (wicking) loctite to seal whatever gap there was between the two halves of the engine case. I redneck pressurized the loctite into the hole, let it set for a little while, put some gasket making material on the bolt shaft and reinstalled it. It's been dry ever since.

The bolts over the lifters were more of a problem, but only because I used too much force putting them back in and stripped the threads on the aluminum engine case.
 
thanks for the info. I'll take a look at those bolts after clean up and a flight with some oil trace powder. I'm amazed that the oil splatters to the underside of the upper cowl.
 
The center cam journal is below the case bolt with the hoist ring on it. Loosen that bolt and tighten it again, you might get a leak (I did) because of pressurized oil trying to make its way out. It spread all over the top of the case, just as in your photo. I did the same thing as Craig. Removed bolt, squirted in some wicking loctite, torqued to spec. Leak-be-gone.

I haven't had a leak from a lifter anti-rotation pin (the black safety-wired bolts) but I suppose that could happen too. Just be careful with loctite there, don't want it getting into the lifter bore.
 
Fluorescent Leak Detection Dye

When I had an oil leak that I couldn't find, in desperation I added Fluorescent Leak Detection Dye to the oil and searched for the leak with a UV flashlight in a darkened hangar. I eventually found a leaking valve cover gasket, but it took a while because the oil from a leak blows all over the engine. I changed out the oil with the dye as soon as I found the leak.
 
Tip.

Down though the years we have found that these small leaks can be hard to spot at first. But once you find that you have one we just clean the area with some brake clean from your local aircraft car supply, then run it for a few minutes to see where the leak is coming from. The trick is to clean very good then run just long enough to start the leak to show it's self. The die trick work well too, but takes a little longer to let it get in the system and start showing it's seeping point. Hope this helps, Yours, R.E.A. III # 80888
 
Locktite here too.

Had a similar leak but either not as bad or got lucky and caught it sooner. Used the vacuum and wicking locktite. No more leaks in last 500 hours.

Mine was only the bolt at the lifting ring. I also sealed the bolt, washers and the hole with Dow 737 after the vacuum/locktite but probably not needed.

Andy
Superior IO-360 Roller - 1350 hours
 
I had similar issue. Cleaned the oil leaks well with mineral spirits and let dry. Sprayed on athletes foot spray on suspected areas. It comes out white. Ground run engine till leak shows up. Worked very well to identify the leak source. The white wipes off easily.
Johan
 
Looking at the oil track would say its from behind the lifting ring. Always hated tracing an oil leak after someone cleaned the engine off. Always likened it to tracking an animal after a rain storm.
 
Not to hijack the thread, but what are the safety wired plugs going into the case about where the lifter bodies would be? I've never seen them before.

The athletes foot stuff sounds like it should work, but what I have used in the past is the developer (spray powder) from a dye penetrant kit after cleaning everything up. Then run the engine for 10 minutes at a time to see where the oil shows up first. It is quite easy to see the origin of the leak that way.

I had a 0-540 leak in about the same area that was a crack that only showed itself with the oil leaking into the developer. Hope that is not your problem.
 
(snipped) Not to hijack the thread, but what are the safety wired plugs going into the case about where the lifter bodies would be? I've never seen them before.

An external clue that the engine is equipped with roller lifters. Those are thread-in pins that engage slots in the lifter bodies to prevent the lifters from rotating in their bores. Which is to say they maintain the alignment of the roller wheel with the camshaft.

My Superior-built Lyclone has the identical setup. Not sure what they look like on a roller cam genuine Lycoming.
 
Patience Required

I had an oil leak that looked very similar to yours. The case appeared to be leaking at the upper split-line. I tried all the methods mentioned above to find the leak, but no joy. Dry when ground running without the cowl, but oily whenever airborne. I had the cowl off about 57 times! Since I tried everything I could think of, I started pulling cylinders as a last resort. I did not get far. I found a small crack on the underside of the first pushrod shroud tube I pulled. Replaced the tube and problem solved! As many know, leaks can be very deceiving and difficult to find. Good luck!
 
Add crankcase pressure?

Steve, manufacturing guys have a saying -" loose, leaks, 'lectrical" are the the greatest issues of production quality.

So - on that . . . while touring a Japanese diesel (truck) engine production line, a curious procedure was encountered. A gallon size can, with a pressure gage was attached to the engines. It pressurized the crankcase and if the engine arrived at the next station, a few minutes away, with a certain pressure it went to paint. If not it, was re-pressurized and sprayed with foaming leak test fluid and repaired. I think the pressure was about 40" of water. I would begin with 20" as we don't know the engines' tolerance for this.

This may work for you, but may not if it is an oil pressure related leak.

Good luck!
 
thanks for the info. I'll put some powder on it tomorrow and take a short flight and hopefully determine the source of the leaking oil.
 
thanks for the info. I'll put some powder on it tomorrow and take a short flight and hopefully determine the source of the leaking oil.

Steve,
Ground run it for a few minutes (till the leak shows up) after you put the powder on. Oil gets moved around so much under the cowling in flight that you might end up with oil in places other than the source. Even letting the engine sit for a while after the ground run might show the source if the leak is slow. I've been there, unfortunately!
Johan
 
My guess is that you might be over-pressurizing the crankcase through the crankcase vent. Not sure what your vent looks like but you might try pointing it aft instead of on the exhaust pipe.

I did this on my IO540 and it stopped a couple of pesky oil drips in and around the accessory case. Just a thought. it may not apply to you or fix the problem, but I thought I'd pass it along.
 
you are the second one to mention that. I'll take a look. Side note, prior to discovering the oil leak I was flying slow with high angle of attack for a considerable time, just for the fun of it. Not sure if that had anything to do with it but that was the only difference in my flying style.
 
this does not work

I was looking for powder and thought this was the stuff. this is not powder but rather some bubble spray. I'll try the athletes foot powder spray instead. Appreciate the tip.

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you are the second one to mention that. I'll take a look. Side note, prior to discovering the oil leak I was flying slow with high angle of attack for a considerable time, just for the fun of it. Not sure if that had anything to do with it but that was the only difference in my flying style.

It answers the question of why it only happens when you are flying, but can't find it running on the ground, if that turns out to be the case.
 
Crankcase Pressure?

you are the second one to mention that. I'll take a look. Side note, prior to discovering the oil leak I was flying slow with high angle of attack for a considerable time, just for the fun of it. Not sure if that had anything to do with it but that was the only difference in my flying style.

Steve,

Haven't you previously posted about several issues with crankshaft seal leaks and blow-outs? I think the evidence is mounting that you may, in deed have an elevated crankcase pressure issue. All these oil leak problems in different areas of you engine are probably not just a coincidence. I would check your breather system very carefully!

Skylor
RV-8
 
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Another suggestion for you to check (easy):

I had a hard time tracing a oil leak looking like yours on my RV7A. I had a Mattituck built IO-360 with ECI cylinders installed. After checking everything and consulting VAF for advice, I opened the #2 cylinder valve cover, removed the nut holding the flat spring to the shroud tubes and found that the spring was so brittle it broke when I removed it. It had zero retaining force to the tubes and obviously the green rubber sealings at the crankcase was not sealing properly. Checked the other three cylinders and all had signs of different degrees of degradation. Replaced with Lycoming original springs and the leak was gone.

/Fredrik
 
Back in the day when I worked for the airlines, we used Zyglo developer to find leaks. We would clean area with MEK then spray developer on the area. It worked great.
 
should have tried the zyglo developer first

well, I purchased athletes foot spray powder but it is clear and doesn't leave enough powder. so now, I purchased something called frost spray.

this stuff doesn't leave much of a powder
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now on to Frost but have to wait a couple of days
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If the rings are not sealing well, you could have some excessive crankcase pressure, you can install this kit and create a vacuum and stop minor engine running oil leaks, I also installed the oil separator, these were installed on an old used engine and it is clean and dry.
https://antisplataero.com/products/crankcase-vacuum-kit-complete

I had a lot of blow-by on the engine I put in my RV-10, a used IO-540V4A5. An oily belly was a nuisance but after about 90 hours the crankshaft seal started leaking also. The crankshaft seal leak got bad enough that I needed to replace it. I bite the bullet and ordered up 6 brand new Superior Millennium cylinder/power assemblies and a new crankshaft seal. That was the end of the oil leak mess.
 
I don't have a picture but oil source confirmed to be the top bolt in the middle of the case under the lifting strap. The roller lifter guides were leak free. The vent line is clear and open at the bottom so no back pressure. It is strange to me how I could develop a leak on the top middle case bolt after 600 hrs but it happened. I'll investigate the green loctite with vacuum remedy.
 
used loctite 290 (green wicking) inside the bolt hole and made a ground run and then a flight. seems to be holding. I think this is some of the loctite wicking out on to the powder spray.

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