Oil all over the hangar floor...

[JimParker256]

For background, I fly a RANS S-6ES with a Rotax 912 ULS. The engine (and airframe) have about 106 hours total time, with roughly 40 of that flown by me in the past year or so. The engine has not consumed ANY oil during the time I've owned it.

So you can imagine my surprise this morning when I arrived at my hangar, and found an oil slick extending about 15 feet from my airplane! (As I'm sure most of you know, even a small amount of oil looks like a huge amount once it spreads out on the floor, so what I initially thought was about a quart of oil was probably more like 1/2 cup or so...) While I was cleaning up the mess, I could not help wondering "Where did that oil come from?"

Once the oil slick was cleared, I removed the cowling and began looking everywhere for oil – or even just "shiny surfaces" which might indicate a leak. I checked the oil lines and fittings, the cylinder heads, the case seams, the gearbox, oil filter fitting – pretty much everything I could see or touch. No oil anywhere.

Then I thought to look at the inside of the lower cowl, to see if it held any clue as to where the oil came from. The visible oil film seemed concentrated in the area below the oil tank. I looked again at the oil lines and fittings, and they were secure and dry. But I did notice a very small amount of oil puddled in the lip of the oil tank lid - kind of hidden under an oil line. It wasn't much oil, perhaps a fraction of a teaspoon. That it did remind me that I had added oil to the engine (less than 1/4 quart) after the last time I flew the plane. I had completed an oil change just before that, and after the flight the oil level was down about the amount that it would take to fill the new oil filter (1/4 qt or so?)...

I do not recall spilling any oil when I added that small amount, but there was some oil on the cover of the reservoir, and I have to assume that I spilled it there... I was using a paper funnel (just moved to a new hangar, and could not find my normal one). That wide paper cone pretty much "filled up" the oil cap access hole, so if it became misaligned at some point, I might not have noticed.

After checking everything out, I started the engine (which lit off immediately, as usual) and ran it long enough for the oil to get to operating temperature, then shut down and checked for leaks again. No oil anywhere.

I parked the plane back in the hangar, with drip cloths all around to catch anything that drips later, and I'll go back and check it again tomorrow. Assuming there is no more oil on the floor (or drip cloths), I plan to run up the engine, then shut down and check for leaks one more time. If nothing is found, I don't know what else I could do to rule out any other source of a leak. I'm fairly certain the oil on the floor came from me spilling it while filling, and just ran down the cowling. The corrective action would be to get a better funnel with a longer neck so that next time I add oil, I'll be able to see that the spout stays in the reservoir opening.

Anyone have any other ideas for things I could or should check before I fly it again? Thanks!

[3Dreaming]

If the tank is over full the oil will come out the breather hose from right below the oil cap. It is kind of odd for the oil level to rise while it is just sitting there. The other thing I have seen is a leaking valve in a carb contribute to an overfilled oil tank with a mixture of fuel and oil on the ground.

[JimParker256]

It's definitely not overfilled – it's at 3/4 level on the dipstick, which is the level I had filled it to... As I said, I'm 99.5% convinced that I caused the whole thing myself, by spilling some oil when I was adding some to the reservoir. I just wanted to see if anyone with more Rotax experience might know something else that I should check before flying it again.

[3Dreaming]

If you pour the oil in too fast it will come up into the neck and run out through the breather tube.

[JimParker256]

If you pour the oil in too fast it will come up into the neck and run out through the breather tube.

Thanks for that comment. I don't *think* I poured it too fast, but I definitely learned a lesson about using those disposable paper funnels - they are just cover up the entire access hole, and I suspect it just got misaligned at some point. The sad thing is, while looking for the cleaning supplies, I found the funnel I should have used in the first place. Sigh...

[drseti]

The sad thing is, while looking for the cleaning supplies, I found the funnel I should have used in the first place. Sigh...

The funnel I always use is an empty AeroShell Sport +4 bottle with the bottom cut out. The neck fits perfectly into the oil tank throat, and I get three new funnels for free at every oil change!

[RV12Heal]

As 3Dreaming noted above if you pour the new oil into the tank too fast it will overflow the neck and make a real mess. You need to have an appropriately-sized outlet on the funnel or carefully monitor/control the flow of oil into the tank so as not to overflow the neck.

[JimParker256]

Yeah, I got back out there, and everything is still bone dry, so I must have just filled it too fast. I was thinking it wasn't real likely, but then I remembered how restricted the inlet actually is, and how large diameter the hole in the paper funnel was - like about 1 1/4" in diameter... So I'm pretty sure that was the culprit. The funnel I normally use has a 1/4" inside diameter outlet.

Thanks for the responses –– and for not laughing at me too hard...

[ShawnM]

Just make sure you check the level again, all 3 liters are supposed to go IN the tank.

[JimParker256]

Oh! Is THAT where it's supposed to go?

Sigh... I guess I deserved that one.

Yeah, I checked the oil level, and it is about 3/4 of the way between "low" and "high" on the dipstick, which is where it was after I added the oil (and apparently dumped some on the floor).