A pleasing engine surprise...

[Pilot DAR]

It has not been possible for me to fly any of my planes since last July, sad, but a reality. Two would be impossible to safely lend out (tricky checkout required), and there's just no incentive to lend out my 150. So they have all just sat for that period. I feel guilty letting equipment of any kind sit, but there was no attractive choice. So, knowing they would sit, I ran them all up, and taxied them around in December, followed by an oil change, and another quick run up. One in the hangar, and two bundled up as much as possible outside for a long and unkind winter.

It's now annual inspection time, and my daughter bought as a birthday gift a really nice, compact wifi endoscope/borescope - one of those Facebook recommended posts. It works wonderfully with my Ipad. What it showed me, when passed into each spark plug hole in my O-200, is not a spot of cylinder rust! Basic steel cylinders with about 800 hours, and the honing marks are as good as new! So now I have confidence that the rest of that, and the other two engines, may not be as bad as I feared.

I once picked up a friend's 150 which had been sitting for nearly a year. I took a charged battery, and gave it a very thorough walk around. When I pulled the prop through, I could hear the piston rings scraping rust in the cylinder walls. The plane had to be moved, so I fired it up. It ran, but was not eager. As it ran, and presumably broke in the cylinders again, it ran well enough to take off. But that was my lesson in try to not leave your engine idle for an extended time.

So I'm hopeful that my two Lycomings are as content as my Continental with a too long period of inactivity. I'm confident that the fresh oil run in December made a difference!

[n5296s]

Wow! I get nervous if I haven't flown my plane for three weeks - about the engine I mean.

[Tinstaafl]

Why not spray some light oil through the plug holes?

[Pilot DAR]

Why not spray some light oil through the plug holes?

'Won't be necessary! There's still wet oil visible, and my intention is to properly circulate engine oil by flying the planes in the weeks to come! Soon, my recovery, and my runway's firming up after a long winter, and wet spring, will coincide, and I'll go flying!

[Cole Burner]

Without wishing to be pessimistic (and in no way trying to teach how to suck eggs) I can tell you from (expensive) experience that Lycomings are more susceptible to internal corrosion problems than Continentals due to the design of the internals.

Your oil changes may have helped keep the rust at bay but generally, running an aircraft on the ground to circulate the oil is one of the worst things you can do - you really need to get the oil up to a proper operating temperature. Turning the engine over for a short period just increases the internal condensation. A google search will find this advice from Lycoming.

Your cylinder walls may have a light coating of oil, but I would be concerned about camshaft, crankshaft and valve mechanisms. There's lots of advice on the internet but it would seem that the best thing to do is fly the aircraft as much as possible - although that's a bit late now!!

[Bob Upanddown]

I would not be so pesimistic but agree the problem with Lycomings is the Camshaft, etc, rather than cylinders.
But so many aircraft see lack of use over the Winter and I bet very few have an owner who worries about it.

[Cole Burner]

I would not be so pesimistic but agree the problem with Lycomings is the Camshaft, etc, rather than cylinders.
But so many aircraft see lack of use over the Winter and I bet very few have an owner who worries about it.

I agree Bob, and I didn't worry about it either, until the performance started to feel a bit poor and our engineer found that one or two of the valves were not opening correctly and found a (very) few bits of metal in the filter. Ended up replacing almost everything inside except the case and the mags!! (IO360) The trouble is it's insidious as you can't see it. The camshaft was not pretty when it came out! Now have an engine dehumidifier fitted via the breather when it's in the hangar - hope that makes a difference.

[scifi]

I think the corrosion may be contributed to by flying in IMC, where the engine ingests lots of water in the air. This can get into the oil, and cause it to go milky. There was a utube video of someone de-coking an engine by letting it take in a stream of water in the carburettor. This found it's way into the oil, past the piston rings it was thought.
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[Ultranomad]

I think the corrosion may be contributed to by flying in IMC, where the engine ingests lots of water in the air. This can get into the oil, and cause it to go milky. There was a utube video of someone de-coking an engine by letting it take in a stream of water in the carburettor. This found it's way into the oil, past the piston rings it was thought.
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I don't think so. Firstly, avgas consists mostly of hydrocarbons and thus contains about 15% hydrogen by weight, which on combustion produces water in much larger quantities than any water ingested from the atmosphere. Secondly, while the engine is at operating temperatures, it is not threatened by corrosion - it corrodes while sitting on the ground. On the other hand, it is indeed beneficial to keep your engine as dry as possible on the ground. Apart from heated hangars and engine dehydrators, it may also be helpful (I do it because it's trivial, but though don't quote me on that) to unscrew the oil cap immediately after landing - a lot of steam comes out while the engine is cooling down. When I leave half an hour or so later, I put it back in.

[scifi]

I like the idea of taking the oil cap off, but it might depend upon engine make, as some fillers are on the end of a long tube. Also the engine breather should be doing that sort of job anyway. I used to fly a c150 that some weeks had milky oil and other weeks had clean oil, never got to find out why... The link to the water ingestion video, that shows water can get into the oil from the carburettor...

https://www.youtube.com/watch?v=2ySSEzqEa_k
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