Q: I’ve been looking at a Lycoming 180 engine in a 1963 Comanche that I am considering purchasing. The engine was new 20 years ago but to date has only 400 hours total. It has been in Australia since 2013, and flew just 13 hours in 2020.
An oil change was completed 10 hours before it came to me to arrange a pre-purchase inspection. Detailed oil analysis was completed which showed a high level of aluminum (70) and Silica (abnormal result). All other ferrous metals were normal levels.
Both magnetos had to be overhauled during the pre-purchase inspection as one failed badly on run up mag check prior to a flight.
Any thoughts on what might be causing the high level of aluminium?
A: My best guess would be we’ve got some corrosion in the cylinders, which is probably a result of the extended periods of inactivity over the lifetime of this engine.
I’d highly recommend conducting a very good borescope inspection of all cylinders as soon as possible.
My thought is that if there is corrosion in the cylinders it’s causing the piston pin plugs, which are aluminum, to be scraped against the rough areas on the cylinder walls caused by the corrosion, resulting in the higher aluminum level in your oil analysis.
However, I’d also inspect the entire induction system, focusing on the condition of the air filter and air box for any possible leaks or areas where the engine may be ingesting unfiltered air. This may be the cause of the high silica reading mentioned in the oil analysis and could also be causing premature wear of the piston pin plugs.
Another thing I might suggest, providing the information is available, would be taking a look of the oil consumption — although I’m not certain there are enough hours on the engine to get a good picture of that.
At this point Paul, I think I’ve provided a few ideas for you and the results of those inspections will dictate any further follow-up action. I might add that these simple inspections should serve anyone encountering a similar situation with their aircraft.