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IO540 Oil seepage

jwilbur

Well Known Member
I've got 10 hours on my -10. About to do first oil change on new stock IO-540-D4A5. I've been pulling the cowl after every flight and I'm consistently seeing oil in the seam between the oil sump and the case on the aft left corner below cylinder #6. It's enough that it works its way around the corner to the back of the engine on longer flights. Also getting small drops on the bottom of the oil return line of cylinders #4 and #6, but does not seem to be coming from the lines themselves.

Thought maybe it was from being sloppy with drips while checking oil before flights but have been very careful about that on later flights and oil still gathering in same places and same amount.

Any suggestions on finding the source? Could it be seeping from between the oil sump and the case? If so, how would drops then get on the return lines?
 
I've got 10 hours on my -10. About to do first oil change on new stock IO-540-D4A5. I've been pulling the cowl after every flight and I'm consistently seeing oil in the seam between the oil sump and the case on the aft left corner below cylinder #6. It's enough that it works its way around the corner to the back of the engine on longer flights. Also getting small drops on the bottom of the oil return line of cylinders #4 and #6, but does not seem to be coming from the lines themselves.

Thought maybe it was from being sloppy with drips while checking oil before flights but have been very careful about that on later flights and oil still gathering in same places and same amount.

Any suggestions on finding the source? Could it be seeping from between the oil sump and the case? If so, how would drops then get on the return lines?

Oil leaks are hard to find and could come from almost anywhere. I'd look at the return tubes from the cylinders and the cylinder base seals.

I chased a significant leak on my O-320 for a decade before I finally identified two loose case bolts mostly hidden by the starter.
 
Oil leaks are hard to find and could come from almost anywhere. I'd look at the return tubes from the cylinders and the cylinder base seals.

I chased a significant leak on my O-320 for a decade before I finally identified two loose case bolts mostly hidden by the starter.

Well, not what I was hoping to hear. .... I appreciate the answer all the same.
 
where is that oil coming from

Those first 10 hours are tough, congratulations on getting through the hardest part of the test flight for me. Its a perfect time to tighten everything up as it's getting "broken in" the case bolts dont need much torque, and if i recall what it was I would tell you, but basically go over every nut and assure they are not loose, if you move the wrench and its tight, move on, if its loose tighten it up. Use some cleaner and go over all that oil, once its done spray foot powder over the area you think its leaking, as Kyle mentioned the oil could be seeping from anywhere aka-the front nose and you're seeing it at the rear.. so anywhere you see oil, wipe down, clean and spray powder. Go out and fly than look and see if you still have that seeping oil, if so, trace the powder and you will see brown over the powder until hopefully you locate the source.. I have 99cent store foot powder and since its cheap I spray it over a larger area. I wont tell you it works everytime, but 8 out of 10 times the process worked for me the first time. I have a rebuilt engine, leaked from first engine start, told its normal, but slowly I have made my normal be no leaks (black fluid on the belly)
Let us know how it works out
Pascal
 
follow-up

Just a follow-up in case another builder has the same symptom.

It was a loose worm clamp on the oil return line to cylinder #5. Easy fix, I'm very happy to say.
 
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