Dodged another small bullet yesterday. Went treetop flying for the afternoon and about an hour into it I could faintly smell oil burning. Pressure was perfect, temp perfect and no smoke anywhere. Landed at KORS just because I had one of those gut feelings.
Sure enough, I was dripping oil from the cowl right below the exhaust - looked in the oil filler hatch and could see it had been leaking from the sending unit. It looked attached, maybe loose? Total oil level was fine so I shot back to my hangar, pulled the cowl.
It seems that just the 120 hours of vibration was enough to rattle the 1/8" copper tube so it cracked at the motor/sending unit. I've done cowl off run ups to check for leaks after oil changes etc too so that probably didn't help. In fact we did another cowl off run up while dynamically balancing the new Cato prop. Everything "looked" secure.
Fortunately it was a simple fix yesterday: cut the copper tube, replaced the little round seal but this time I SECURED the bulk of that coiled tube to keep it tied to the nearby engine mount etc.
It could have been a longer down time had it happened on a trip (or worse, if the oil started squirting on the exhaust) - it felt nice to catch it soon, just because I could faintly smell oil burning.
Anyway, it seems like all my bullets come in small, preventable fixes - like the missing cotter pin on a throttle linkage crown nut I discovered on my brand new IO-360 200hp on my RV-7. I bought the plane new but built and put a couple hundred hours on it when one day while changing the oil, I was just looking the bottom of the engine and linkage over while waiting for the last drop to drip and saw the throttle linkage crown nut without a cotter pin!!!!
That could have been a horrible surprise eh? Imagine no throttle control on take off, or landing or flying over unfriendly terrain. Bummer was it was only one little tiny cotter pin.
Pete, I don't know if you guys secure that copper oil line from the sending unit down now (I have the #2 Carbon Cub off the line) but fella's I think it's a good idea because there's a little weight in that loop of line hanging in mid air and it doesn't take much to crack a puny 1/8" copper line.
Simple stuff! Ugghh....it reminded me yet again, it pays to pay attention - all the time.