Saturday, February 28, 2015

Chasing Oil

It took a few months longer than I'd hoped-- hey, it's cold in Minnesota and you can only breathe so many kerosene fumes from the heaters! -- but the annual condition inspection has been completed. The goal has been to slowly move the annual date to the middle of winter from its original June so that I can have the plane "grounded" when I'm not likely to fly anyway. Mission accomplished.

I didn't find anything serious during the inspection, but a few weeks ago, I did find more oil in the cowl than I care for.

Some comes from the oil screen plug, which has a particular torque value that always seemed too low. It's something like "finger tight and 135 degrees," or something.

But it's hard to find the source of the drips because the oil flies all over the place in the cowling once it's pressurized by ram air.

For example, this is the picture of things a few weeks ago when I first started exploring:

Looks to me like it's coming from that cover near the oil return, and therein lies the problem. It's pretty hard to figure out for sure where it's coming from.

But then Dan Baier had a suggestion. Clean up the engine and wipe off the oil, and then spray things with a foot powder. So I did. I waited for it to dry -- it provides a "white" cover -- then took the plane out to the ramp and ran up the engine for 10 minutes.

This is roughly the area:

Things look pretty good, right?

I should point out that the worst thing I ever did was what everyone suggested I should do: put a "whistler hole" in the oil breather tube. It spits out oil (and water) which gets everywhere. It's nearly impossible, it seems, to get the tube itself to drop it drips on the exhaust stack (where it would burn up) because of the engine mount which gets in the way.

I suspect there's also a problem -- well, not really a problem -- that with this engine, if I fill to capacity (about 8 quarts) with oil, it immediately pukes a bit of it overboard. I've heard that's the case with a lot of airplane engines.

I did find one area of concern, and it's the case. Here's a shot from the front.

You can probably see a little oil coming out near where that bolt and nut are. That would account for the occasional drip of oil I see in the front of the engine.

Now, the problem here is it's pretty impossible to get wrenches on either one of those locations, although I did and gave it a little tug; it was pretty snug.

A check of the rest of the engine did not reveal anything suspicious, so I put the cowling back on and took her flying for the first test flights post-inspection.

Afterward, I just looked in the back of the bottom cowling and saw a few drips of oil directly under the oil strainer and the usual mess around the breather tube, including drips of water. I hate that breather tube!

I also determined that what I thought was oil running down the gear leg when I first started the firewall-forward inspection, was probably avgas, coming out of a small drain hole I made in the filtered air box. I've always gotten fuel drilling in there -- possibly after shutdown or from overpriming. Even after 175 hours, I'm still learning things about what makes the engine happy with starting and I see this as a lessening problem.

But the oil drips cause me concern anyway because I don't really know the difference between routine and worrisome. Airplane engines are dirty things. Beautiful. Just dirty.

But at least mine doesn't have athlete's foot.

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