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Oil mess mystery - any ideas?

gossend

gossend

Well Known Member
Patron
This from en email posted by my friend and owner/pilot of a 180HP IO360 RV-8. I looked at it myself and I'm stumped.
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"For those that have been asking and trying to keep up. As you know yesterday I flew it for 1.3 for its first test flight post #2 cylinder failure and new valves installed. Flying great, just crossed over 1.2 at 25 squared, everything in green but no high temps although I am trying to get them there. Oil pressures had crept from 85 down to 45 (but we believe it is the gauge as it has been doing this). Tower calls said they saw smoke coming from the plane so I landed. Got out and the whole left side is covered with oil and puddles dripping off of the bottom. The smoke was all the oil hitting the left exhaust stack. So today we pull the cowling, no obvious leak places or loose fittings. Clean it up, pull it out and run it at 1800 rpm for 4 min shut it down, no leaks that we can see. Pull plenum to insure nothing is hiding under it. Dry as a bone. Decide to cowl it up and go test fly it. Fly it for 30 min 25 squared flys great, generates plenty of power, everything in the green.(oil pressure creeps down from 85 to 62) Land left side is now super soaked in oil streaming with airflow of wing past aft of wing and left strut puddling oil by the left main, meaning it is getting worse. Pull the cowling expecting it to be evident and the left side of engine covered in fresh clean oil. But no obvious leak. One person says he has been working on engines for 43 years and has no idea where all that oil is coming from unless it is a cracked case or a crack in the head or heads that opens up once it gets hot. Note that both #2 and #4 look clean and absolutely no oil anywhere near the base. No idea how to proceed at this point. If I replace the cylinders that still may not stop the leak. It is quite the mystery in this ongoing saga I wish would end soon! Anyway that is the latest update. Thanks for all of you that have been helping and asking about me, appreciate it. Hoping an idea will come to mind after a nights rest."

It's not the prop seal or the breather, not the drain-back tubes, not the rocker box gaskets, and yes, the dipstick is secure (wrong side anyway). I'm out of ideas. Help?
 
Oil cooler or lines/fittings?

Examine everything that has oil flowing in it...
Wash the whole engine clean with degreaser and maybe put some leak detection dye in the oil and only run it on the ground.
 
Wash the whole engine with degreaser, and when it's dry dust the entire thing with baby powder. Run it in stages. Start, shutdown, check. Start, idle 30 seconds, shut down, check. Build up to a runup, and an extended runup.

I wouldn't fly it again until the problem is found... If it's a crack that's opening when hot, it's a crack that will propagate. That means the end game is a cylinder departure or a case hole... In any case, be sure it happens on the ground if it gets that far.
 
oil cooler maybe?

maybe the oil cooler is cracked or loose oil cooler connections?? I had a bad oil leak once that was a bear to find. I finally tracked it down to the remote oil filter adapter. The leak only showed itself during flying conditions (time and rpm). I couldn't find it on the ground. I used the baby powder trick to find it.
 
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Think pressure build up . . .

If #2 was off, you might consider that there is a pressure build up due to a loss of drain back area. Maybe, take off the rocker covers and ensure that the drain back holes are open - blow air down that hole(s) just to make sure.

So either a pressure, or a fluid build up for some reason then it reaches a point with time that it pushes out past a gasket. You could blow back through the blow-by tube to be sure.

That's all I have at the moment. When I built engines. I did it in a single work session. And at stages I would stop and mentally replay what had happened and remember each step. If your mechanic (you?) did this you/they should remember what techniques they use in the tear down/build process that could have this effect.

edit: question, did the time to leak follow a temperature rise of the oil? Could it be the vernatherm releasing oil to the cooler at about this time?
?????
Good luck, don't keep flying and hope it goes away.
 
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I had a similar confounding oil leak earlier this year. Turns out it was from a cracked AN oil pressure fitting at the engine. For some reason I can't remember I used an aluminum fitting instead of steel.
But that is on the right side of my engine. The pressure dropped just as you describe.
 
Oil cooler

Without more info oil cooler would be my guess. The cooler is bypassed until the oil temp comes up. Most likely it is not showing itself until that circuit is open.
Ryan
 
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