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Just went through this with my Cherokee motor.
This is what my cam lobes looked like - ![]() And the tappets (ugh!) - ![]() It was time. Doing it early is less costly than watchful waiting. BTW, the Lycoming school was great for doing the work (with an IA supervising & signing off). Dan |
Why not follow "local in the business" advice?
The engine sat from the date of overhual, July 1999, until date first flown, in January 2010. During that time it was in a preserved state and in a dry climate. So, not sure it strictly meets the criteria of an inactive engine. Since first flown it has flown weekly. If I could I would fly it every day, but increasing fuel costs require some curtailment of my flight activities.
I have flown 8 hours out of the recommended 10. It's not only the local business recommendation but it is also what I believe the Lycoming recommends (Lycoming Flyer, pg 80). However, that does't make it any easier to fly those hours when it is also stated that metal in screens and filter can lead to catastrophic failure (ibid). This is something that I take seriously. I am trying my best to employ a logical Risk Management process here and as I interprete the data it now indicats that risk increases on every hour flown until the source and extent of the abnormal condition is known. The worst case senerio, catastrophic failure, is unacceptable. Granted, "On small amount of shiny flakes or small amounts of short hair-like bits of magnetic material. Experiance has shown that engines are sometimes pulled unnecessarily." (ibid) |
Pulling a cylinder to have a looksee is really not a big deal. We're not talking about a complete teardown.
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Which Cylinder?
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For me it doesn't matter since I have a borescope. But I would go with #2.
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Additional relevant information
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I continue to review available information and have noticed a difference in the way Champion and Lycoming recommend that a oil filter should be examined. Lycoming recommends spreading the element out and examin. Because the metal is so small and fine, Had followed that procedure I would not have found the metal. It was not until I used a magnet that metal became apparent. I did find one NTSB accident involving sudden engine stoppage of a O 360 on an RV-6. It occurred in March 2012, in Bow, WA. Only a preliminary report is available. Though Washington is in a more corrosive moist area than mine, it may be relevant to the metal in oil filter issue. |
I'll ask questions rather than speculating since I know very little about these engines:
1. Does the filter inspection require flushing the filter element through a filter paper? I have not heard anyone else doing so and was not shown to do it this way. Is this normal procedure? It seems rather extreme and may be over indicating the problem. 2. You say you are using no additives in the oil, but have you recently switched to a detergent type oil? Ie from straight mineral to W100 or W100+. If so then you may have released a buildup of sludge which may have trapped some of this. I did read a Lycoming sb that delt with this issue, iirc they required an oil change after 5 hours because of the release of the sludge and what it contained. That said, if I were in your boots I would probably get a specialist to look over my shoulder while I pulled a couple of cylinders to inspect the cam and lifters. Good luck, |
Filter examination procedure and change in type of oil
From Champion AV-6R http://www.championaerospace.com/***...R-Nov2004.pdf:
Use the following recommended procedures to inspect full- flow oil filters. ? Remove the filter from the engine and place it on a drain tray. Allow oil to drain through a clean cloth to determine if foreign material drains from the filter. ? Using the Champion CT-923 Can Cutter, open the filter . . . . ? Using a clean plastic bucket containing approximately one pint of clean Varsol, swish the filter element around in the Varsol to loosen entrapped metal or other contaminants. ? Using a clean magnet, work the magnet around in the Varsol. Ferrous metal particles in the solution should adhere to the magnet for inspection. ? After all ferrous metal particles have been retrieved with the magnet, pour the remaining Varsol through another clean shop rag, and any nonferrous metals should be detectable in bright light. This is certainly a more substantial examination of the filter than that described in Lycoming Service Instrction No. 1492D. However, I am unable to determine if it is "over indicating the problem." Phillips XC 20W 50 has been used since overhaul. |
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You will play **** getting the metal off the magnet. I cover mine with a thin piece of surgical glove. |
There is a good EAA Video on Oil filter removal, inspection, installation.. it's 9 minutes.
http://bcove.me/qxaiqkdw |
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