Oil leak detectives

Just when I thought all of our maintenance woes were behind us, I opened the hangar door.

Silly me.

Here’s the Tale: Rio and I had mapped out a good training flight. Don’t ask me the details now, I’ve already forgotten them, but I certainly remember the rest of the day. We grabbed a light breakfast, loaded up Grandma Jean and R2D2 (her oxygen concentrator), and headed out to the airport. Grandma wanted to see Lisa’s recent renovation of our Third World airport terminal and said she’d hang out there and soak in the vibe while Rio and I flew for an hour or so.

It was a lovely morning, not too early and not too late, neither too cool nor too warm, and the wind was just barely stroking the surface of the earth with a lover’s touch.

When we arrived at the hangar we parked in front of the double doors so Grandma could see her airplane. I unlocked the padlock, then I took the right door and Rio the left. We dramatically pulled the great doors open at the same time—like the curtains in an old fashioned theater at the start of the show—revealing Tess, the morning light kissing her canopy. Above her the flags in the hangar undulated gently in the morning breeze, and with her sharp wing dihedral she looked ready to jump into the air… Except for the fact that she was sitting in a puddle of her own oil.

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Damn. What’s this going to cost me?

Actually, as we know we have a soon-to-be replaced leaky gas tank, at first I mistook the dark pool for fuel. But kneeling down and running a finger through it, I found it to be slick, honey-colored oil. What the….? The pool was centered under and around the front nose gear. Where did it come from?

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Now oil leaks from Continental engines aren’t rare. Some folks joke that like a Harley, if it ain’t leaking oil, it’s surely out of oil. But this was something new. The sides of the cowl were clean, as was the front wheel pant, plane’s belly, and the hangar floor underneath the breather tube. Adding to the mystery, after our last flight the week before, Lisa and I had stayed in the hangar a good two hours, cleaning up the plane, listening to the CTAF, smoking cigars, and soaking in the whole airport vibe; and in those two hours no oil had leaked. So how did this much oil escape an engine that’s not running? And how’d it get from the engine, where it belongs, to the floor, where it does not belong?

Of course, oil is a funny thing. A little spilled oil looks like a lot. To my many-times-bitten now crazy-shy eye, it was the entire contents of the oil sump. In reality it wasn’t even enough to detect missing on the dipstick. Still, not understanding what was going on, I cancelled our planned flight. Rio thought I was being a bit of a wuss, but he didn’t argue the point, and thus began the Great Oil Leak Investigation—a tale not likely to knock Sir Arthur Conan Doyle out of first place anytime soon.

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We opened both sides of the cowl and looked for oil. Naturally, as we rarely clean the inside of the cowl, there was oil everywhere. Shining my handsome new Tessie-blue 100-lumen Eddie Bauer aluminum flashlight around inside the engine compartment I felt like an explorer of yore trying to trace the source of the Nile.

Let’s see here… These two little streams of oil seem to connect to that stain here, which seems to come from up there, so the oil must be leaking from the… alternator? No, that can’t be right! I took a ton of photos with my iPhone and emailed them to my beleaguered mechanic (who responded two days later that it didn’t look like that much oil to him, and if it was him, he wouldn’t worry about it). Then, using many pale blue paper shop towels I cleaned the inside of the engine compartment better than anyone had in the last 71 years.

I placed clean folded towels in various strategic locations and we left for the day, Rio predicting that we’d come back to a clean airplane and clean towels.

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He was half right. A couple of days later we came back to clean towels, and more oil on the floor. It was as if the oil were welling up from the concrete below the plane. I had a brief vision of the start of the Beverly Hillbillies, with me in the role of Jed Clampett, but I knew I hadn’t struck oil. Tess was leaking it from somewhere.

But where?

One of the leading contenders from the previous week had been the gasket between the fuel pump and the engine case. There was a clear sign of a leak there, but how that gasket could leak in the absence of engine pressure was a mystery to me, and now the towel below it was clean. The other contender was the valve cover on the number one cylinder, which was also leaking a drip or two, but it could hardly have been the culprit with a resting engine, and again the towel there was clean. And yet, there was fresh oil on the ground.

Adding to the mystery was the fact that oil spilling pretty much anywhere from inside the engine should come out of the bottom of the cowl where the front fork comes through the metal surrounding the engine, but oil exiting the compartment there would stain the front wheel pant, and it was clean. Complicating matters was the fact the oil had just been changed and it was still clean, making it almost transparent.

Lying on the concrete, trying to avoid getting oil on my shirt, I carefully studied the front fork. It had a smooth sheen of oil on it, as did the aft scissors assembly. Mentally, working slowly backwards, I tried to envision the path of the oil, and it led me to the oil sump drain. Suddenly the clouds parted, the sun came out, and it all made sense.

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When the engine is off the oil drains out of the case and down into the sump. The only logical place for oil to leak from when the engine is powered down is from the sump. I reached in and fussed with the quick release valve used to drain the oil out when changing oil. Of course I had no idea how it worked normally, which made it challenging to see if it wasn’t working right. Twisting, tugging, pulling, I managed to accidently open it. A gush of gold oil flowed out. Mesmerized, I watched its travels.

Eureka!

As the little stream twisted and turned around various obstacles in its path all the mysteries fell by the wayside. I’d found the source of the Nile.

Now the challenge was to figure out how on earth oil was leaking from the drain. There were three possibilities. The mechanism itself could be failing, it wasn’t closed right, or it might not be screwed on exactly tight enough. To rule out the last possibility, following instructions from one of our two mechanics, I took a paper towel and wrapped the upper part of the drain like a mummy, using a zip tie to secure the towel.

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Then I flew. And left the towel in place for a week.

When I returned, there was new oil on the floor and the towel was clean. Well, not clean, but not oil soaked. A new sump drain was ordered and my guys will put it in this week while Tess is visiting them for a new header tank. Once that’s done, I’m confident that all our maintenance woes will be behind us.

Until I open the hangar door again.

 

 

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