Diagnosing Oil Leaks

[jaredyates]

Has anyone found a good way to troubleshoot the source of an oil leak, particularly in the very front of the engine? I have a small leak there that I've been living with, but would rather fix. I have tried cleaning the area and dusting it with baby powder, but without taking the prop off it's pretty hard to see where the oil is coming from. My engine sat for quite a while between the rebuild and the first run, so I'm suspicious of the crank seal. Have any other builders encountered anything similar?

[Barry]

Jared,

Go to the local parts store and buy some tracer dye for the oil. Then use a black light to find the source. The fresh leak will glow when you hit with the light. These kits are very inexpensive.

[rv8bldr]

Hey Jared

That sounds like a crankshaft oil seal at the front of the crankcase. I had the same problem with my IO-360-A3B6D on my RV-8. It was kind of an insidious leak that was hard to trace.

Here are a few links on the subject:

http://www.lycoming.com/Portals/0/techpublications/serviceinstructions/SI%201324C%20(05-26-2009)/Crankshaft%20Oil%20Seals.pdf

http://www.vansairforce.com/community/showthread.php?t=41030&highlight=crank+seal

http://www.eaa.org/experimenter/articles/2012-02_sealtool.asp

[Battson]

That is a CS (oil filled) prop up front? It's semi-normal for them to leak a bit as they settle down.

I found when you're flying and there's high air pressure, high flows of engine fluids, high velocities of air etc etc etc it's almost impossible to be certain where a leak is coming from.
Mine was the oil return lines, but it looked like it was the front cylinders or the firewall which got oiled every time....

[jaredyates]

Thanks for the help! I agree about the difficulty in finding the source. The oil is definitely inside of the cowl, which makes me doubtful about the prop. I did get a little bit of grease leaking from the prop in the first few hours. I've ordered a seal, so sometime I'll see if I can get it swapped out.

[rv8bldr]

Hi Jared,

I was nervous about doing my seal, but it wasn't that big a deal (hey, that rhymes). I removed my spinner and prop (Catto, so it was WAAYYY easier than a CS), then used a combination of hooks/small screwdrivers/etc to grab the seal and pull it out being SUPER careful about not scratching something. Once the seal was out, I just cut it with snips to take it off the shaft. I then made sure that the journal where the seal sat was sparkling clean and smooth in prep for the next step.

The new seal had a spring that sits in a groove on the back side of the seal. It has a hook arrangement on it so you can put it around the crank like a necklace, then hook it together. Then I put a plastic grocery store bag around my prop flange to make it slippery and carefully worked the seal over it. Once it was over, I slid the spring thingie into the groove on the back side of the seal, applied the glue to the circumference of the seal and slid it in.

That's pretty much it. My crankshaft seal starting leaking after about 250 hours and hasn't started again yet (another 200 hrs).

Cheers

[jaredyates]

I thought I'd post a follow-up on the crankshaft seal. I replaced it yesterday and flew for about 2 hours today (first Young Eagles, 12 in fact) and so far it isn't leaking. When I got the prop off and looked in at the old seal, it was pretty clear that the oil was coming from the crankshaft-seal junction. Getting the prop on and off was most of the work.

[marcusofcotton]

Congrats on finding the source with certainty and getting it taken care of. Although not frequent, it still seems too common for fresh engines to have a leaking crankshaft seal... wonder why?

[jaredyates]

I have worked on some old motorcycles that use a similar seal technology, and it seems like they are prone to leaking after years of disuse. If I had started running the engine soon after delivery, perhaps it would not have leaked.

[Battson]

Glad to hear that you've resolved the problem! Hopefully removing the prop is less work than regularly lying on your back cleaning spilt oil from the belly!
I agree taking the prop off can be a bit of an ordeal at times - keep a big plastic rubbish-bin handy to put the prop on.