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Oil in cylinder, other cylinder issues
I have a mid time (1000 SFNEW) IO-360 Lycoming engine.
Recently oil consumption has increased from about 1 quart/10 hours to about 1 quart/ 5 hours. For a long time we've collected oil on the bottom #1 plug but it seems like its worse now. In addition, we've had high aluminum levels in our oil samples for several years but now showing high iron and other harder metals. Blackstone is saying that our oil sample indicates high blow by and seems to show that a piston pin plug is now rubbing on the cylinder. The oil filter is still showing only a small amount of metal. The IA at the A&P school says the amount of metal in the filter is expected for any midtime engine, not excessive. Since the last couple of Blackstone reports have indicated the pin plug may now be rubbing on a cylinder we've been doing a boroscope every 10-20 hours of flight. However, the boroscope is still coming up with nothing (we have Nitrite cylinders and the cross hatching still looks great). Compressions were all very high (enough that the A&P is always a bit suprised to see them so high all around for a midtime engine) So, I'm wondering where I should go from here. 1) How can I tell if the oil from #1 is coming past the valves or the rings? 2) Is there any reason to believe the oil in #1 cylinder and the oil analysis issues are related? 3) Other than the oil usage in #1 I really have nothing to suggest one cylinder over the other for making metal in the oil sample. Should I just address the oil in the #1 cylinder and ignore the sample report until there are other signs (filter, boroscope, etc)? Or, should I just start pulling all cylinders (I'm told its about 10 hours of labor per cylinder ) until I find a busted pin plug? 4) I spoke with Lycoming. Although they didn't have any suggestions on how to determine which cylinder has the bad pin plug, they did mention that if we find the issue before there is much scraping on the cylinder we should be able to simply put the cylinder back on (and avoid sending it to a cylinder shop, saving lots of $$$). So basically the sooner I find this, the less expensive it will be (well, I guess if I have to pull 4 cylinders before I find it, it might not be less expensive). 5) If I find a pin plug broken what should I do? Several A&Ps have told me that pin plugs just work loose on Lycoming engines and I should just replace the busted one and forget it. Others have said I should do something to the engine to prevent the next plug from working loose (not sure what). -Robert |
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