IO-360, 900 Hours, but...
Posted by FlyRvR@reddit | flying | View on Reddit | 45 comments
Only 20 in the last six years, hangared, kept clean in a desert environment.
How worried should one be about cylinder/crank corrosion?
poisonandtheremedy@reddit
My O-320 was overhauled in 1971. Flew 750 hours up through 2005 then sat for 10-12 years on the ramp. Got flying again in 2018 (20 hours) before sitting again until 2022.
I've since put 400+ hours on it (100+ per year) and not a hint of corrosion.
Desert life is damn good for old planes.
EngineerFly@reddit
I’d treat it as a runout engine. Make sure the price is set accordingly. Also make sure you have the cash in hand for an overhaul. Find out how long it takes to overhaul that specific model, and if the big overhaul shops have engines for exchange.
Finally, if you were buying my airplane and asked to remove a cylinder to inspect the camshaft, I’d say no. That’s too invasive. Cylinders are not inspection ports, and are not designed for easy removal.
Buying a used airplane is a bit of a crapshoot, and buyers need to have the cash to handle the majority of the likely outcomes. I speak as someone who bought an old twin knowing that both engines were past TBO (in both hours and years) and that I’d be painting it too. I had the cash in hand, so I was not too upset.
FlyRvR@reddit (OP)
Yeah, I wouldn't pull a cylinder in a pre-buy. I agree.
That's the big catch--we "think" we have the budget for the plane plus an engine, but I think the thing that is making me tread very carefully is the total number of unknowns. I'm kind of looking at it as shifting from unknown; to willing to take a bet; to it's a safe bet; to it's never a sure thing, but pretty certain. I'm between take a bet and a safe bet with my budget. ...I suppose that might make sense...
smoothbrian@reddit
If it's a Lycoming, camshaft and lifter corrosion is a real concern. Best thing to do is an oil analysis. Next best option is to pull a cylinder to borescope the aforementioned parts. The reason that's option 2 IMO is that you're creating the potential of maintenance-induced issues. Oils leaks and even spun bearings can be caused by improper cylinder installation and removal. Better not to open her up if you can avoid it. If you do decide to do it, make sure the work is done by someone who knows what they're doing.
Pulling the bottom plugs and borescoping cylinder walls gives you an idea of what the other insides may look like. If that looks good and an oil analysis doesn't indicate any lifter or cam degradation, I would send it.
If the inactive years were in a very dry environment, you don't need to be as worried but I still recommend investigating.
FlyRvR@reddit (OP)
Definitely will investigate. These are exactly the things I was planning on doing. The aircraft has been hangared here and obviously kept clean and safe since 1977, but not flown much. The engine time is from the 1990s. I don’t yet have full logs. But I will by Wednesday evening.
What is the best way to get an oil sample without removing the filter? My idea being to go take a look, get the sample and have it sent off while the plane goes in for a pre-buy.
Filter inspections on the annuals show clean, but I don’t yet have details on whether the bore scoped in the last year or two.
172drivr@reddit
the thing is that the oil sample is not going to be valuable until the engine has run again. it also could show some metals from sitting that stop appearing after another oil change and the engine could still make TBO.
ask your mechanic what can be borescoped without removing a cylinder. on some engines you can see the cam through the oil filler tube. depends on the engine.
FlyRvR@reddit (OP)
Well, the good news is that even though the time is very low, the engine has been run. I don't know exactly how much, but he does run it and fly it short hops, at least for each annual.
thatTheSenateGuy@reddit
That’s not a good thing. You need to heat up the oil to remove the moisture. It’s better not to run up or fly if you don’t fully heat the oil; if moisture is not evaporated you have moisture in an enclosed metal space. (Not good)
FlyRvR@reddit (OP)
Yeah, I can see how that works. So the only hope would be if he is actually running it long enough to burn off the moisture. Which means the only hope still comes down to the visual inspection of the cylinders and cam and such.
smoothbrian@reddit
I agree. Short hops are generally worse than sitting. Under 45 mins would make me worried
FridayMcNight@reddit
You can drain oil from the crankcase quite easily. Just beware that a single oil analysis won't tell you much. the value in them is more about trends, and I'll say from my own experience with IO-360 lifter failures, in both cases the oil analysis didn't show anything meaningful til after there was a bunch of metal in the filter.
A bore scope during the pre-buy is very do-able. Doesn't take that long. Also, replacing and inspecting the filter really isn't that big a deal. I'd be surprised if the seller balked on that at all. You'd need to buy the right one and show up to the pre-buy with it. But I'd trust that a lot more than oil analysis.
And also, like I said in my other comment... just price it like the engine is run out. Odds of cam/lifter failure are high. Whoever buys it will find that it runs great and everything looks good... for about a hundred hours.
FlyRvR@reddit (OP)
I totally agree, and I've heard that 100 hour number before. The other aircraft I've looked at all have engines at TBO, so it really is more about buying the plane, pricing for the engine.
The oil analysis would, I hope, be the thing that either shows nothing without multiiple tests, but might show one or two numbers that are peaking. Copper, for instance. I would think that certain numbers would be alarming even without a trend. But then, you're probably right about that being caught in a filter analysis anyway.
FridayMcNight@reddit
I've had two IO-360 engines that had the infamous lifter spalling issue. Both were making metal that showed up in the filter. Neither showed anything unusual on the preceding 50 hour oil analysis.
One of these failures was anticipated. I bought an airplane in a situation much like yours. Few hours in preceding 5 years, hangared in the desert, etc.. People around me gave me the same advice I gave you. "Price it like is has a run out engine; maybe you'll get lucky." I'm glad I listened to them. Got a great airplane, overhauled the engine shortly after buying it, and the price of the overhaul was built in.
Don't try to convince yourself that it's gonna be OK. Assume that it will fail, and be comfortable at your offer price with spending an extra $45k in the first year on overhaul.
What kind of aircraft you buying?
Canadian47@reddit
I would start by doing a borescope of the cylinders/valves and then get a good look (however you can) at the camshaft and lifters.
jacenborne@reddit
There's no way to see the camshaft and lifters on an IO-360 without removing a cylinder unfortunately.
Canadian47@reddit
I wasn't sure but I was thinking that as well, you may be correct.
The seller may not be comfortable with someone pulling a cylinder. If I remember correctly on an IO-540 one of the middle cams does double duty and in that case as a buyer I would probably insist to check that one.
7w4773r@reddit
Roughly half the cam lobes on any flat lyc do double duty. Opposing pairs of intake valves line up and they use a single intake cam lobe for both sides.
Brotein40@reddit
Isn’t this something they’d catch on pre buy? Genuine question
x4457@reddit
Depends entirely on how thorough of a pre-buy you negotiate and pay for.
Brotein40@reddit
Damn there are different levels to pre buy? What is this do I also need to buy premium battle pass season pass ?
FridayMcNight@reddit
There aren't any levels to pre-buy. There's no well known inspection list. It's whatever you tell the A&P to look at. And if you don't tell them anything specific, it's whatever they think you would have told them.
x4457@reddit
A pre buy is whatever you want it to be and whatever you're willing to pay for. There is no "standard" and there's no universal guide.
FridayMcNight@reddit
Not really. The big corrosion concern is cam & lifters, and you'd need to pull a cylinder to visually inspect the cam/lifters on an IO-360. Most sellers would not want some random A&P doing that.
FlyRvR@reddit (OP)
You would hope. I ordered a pre-buy on a plane a few weeks ago. It was annualed and worked on by a place that has a national reputation for THE place to go—two hours into the pre-buy we called it off because they already found at least four items under the cowl that were unapproved maintenance. Even parts being made from recycled, non aviation, materials. This was all stuff that even I would have picked up on, yet the famous shop sold it to the owner without mentioning any of that.
So a pre-buy is important.
FridayMcNight@reddit
Price it like there is cam/lifter spalling. >90% chance there will be. Upside: you'll know the condition of the engine after it's overhauled.
Mountain-Captain-396@reddit
Lot of people don't know that the TBO for an IO-360 is 2000 hours OR 12 Years. Your engine is well past TBO, so keep that in mind when negotiating the price. Whether or not its servicable is a question for someone more experienced than myself.
FlyRvR@reddit (OP)
Right -- i'm approaching this as if it is out of time, and the inspections and negotiations will follow. It's otherwise one of the cleanest, well-sorted airframes, panels, cabins I've seen in my budget. (You can always spend more to add more glass, but this one is updated just enough.) So the price is not "bad" but it needs to be adjusted according to the engine.
friedrice33@reddit
It doesn’t matter if it’s hangared the elements will still affect it. If the engine has not been properly preserved (doubt it was) corrosion is going to be a huge issue. Also, lycoming suggests engine overhaul after 12 years due to seals starting to break down. You can get an A&P to pop a jug off and inspect the cam for corrosion and wear. There is a way to do it with a boroscope through the oil filler tube, but it’s quite tricky and can require an expensive borescope to do it.
aftcg@reddit
Contemp prior to investigation. Borescopes are cheap af. Check Amazon. TBO is a myth, has to do with seals and more to do with lawyers. Popping a jug off just to look for corrosion is massively invasive for a prebuy. An oil analysis after a few hours of flying will be much more revealing
friedrice33@reddit
To perform the cam inspection through the oil filler tube you need a 4 way articulating narrow borescope which can be expensive.
aftcg@reddit
I guess "expensive" is subjective. $350 on a 4 way teslong 720 isn't expensive compared to my 3/8 snap on set lol.
dopexile@reddit
Gravity removed all of the oil from the cylinders and camshaft, allowing them to be exposed to corrosion. Borescope and inspection is probably your safest bet
flyingron@reddit
All the rubber on the engine is likely shiat at this point as well. Fuel lines, gascolator gaskets, etc...
aftcg@reddit
It's Lycoming in the desert. I'd probably not care if the price is right. Fly it for a few hours for the owner so you can get a a good oil sample
RecheckFeePlease@reddit
I believe Lycoming recommends IO-360 engine overhauls every 2000 hrs (2200 if factory) OR every 12 years. Not an A&P so I'd defer to one's judgement. I would definitely have someone look at it
aftcg@reddit
TBO is a myth
Antique-Kitchen-1896@reddit
The 20 hours in the last 6 years. How many hours were ground runs after annual?
Some people have this idea if they run the engine on the ground it’ll keep it good. Often what they actually did was introduce moisture from combustion and left the engine too cold to evaporate it off.
The oil analysis idea isn’t bad from point of view of seeing the water content in that oil. Will be one indicator of if there are increased risk of corrosion. You might want to take two samples one from before running it and one after. To get and idea how much metal got into the oil from the run. However, it is still guess work. Actually a large part of ownership is guess work on how good your engine is. Kinda disconcerting on and single engine aircraft but it is part of the experience lol. I mean in a car oil leak is immediately indicative of work needed, on a Lycoming they say L stands for leak. I have seen a 172 front wheel pants covered in oil. And it’s still on condition but the owner is replacing the old conti 6 cylinder with a O-360 soon.
With an engine history like that I would ask about pulling a cylinder to check inside. You might get a firm no on that idea as it can been seen as risky. This is the only way you can be sure the cams and lifters are good. Also check the dry tappet clearance while you are at it, not often checked and could be off resulting in subtle issues or serious vibrations.
When you borescope the cylinders check for the amount of honing marks still visible. Look it up for what it should look like. The cross hashing scratches should be present and mostly intact. The hash marks being worn out indication of problems or old cylinders. Without the marks the walls can’t hold oil for lubrication and you’ll need to replace the cylinder soon. Also check for valve burn marks. Ideally the pattern on the valves should look circular. Non symmetrical burn marks can indicate valve problems.
Check the papers to see if the engine has the harder valve guides. Older soft valve guides have a 400 hours wobble test recommended. If so see when it was or if it was done.
Beyond the engine if it sat for such a long time you’ll need it to be throughly inspected for other issues. What airframe is it? There are lots of model specific things you need to be looking out for.
ChestertonsFence1929@reddit
Regardless of hours or storage considerations, Lycoming recommends an overhaul every 12 years. I’d treat this as if the plane had 2000 hours on the engine.
Antique-Kitchen-1896@reddit
Only from the negotiating point of view. Practically the engine could be operated under on condition for years to come.
FlyRvR@reddit (OP)
By the way, I should say that the aircraft has been hangared like this for many, many years, and it has been consistently annualed. It is in annual now.
Worldx22@reddit
30 year old overhaul = time on engine doesn't matter. Price it as a run out engine. Whatever life you can get from it is free flight time.
SimilarTranslator264@reddit
Yea calendar time is way worse than flying time.
shrunkenhead041@reddit
How old is it, age wise?
It's in the desert now, but was it always in the desert?
Unless the let you pull a jug for a lifter and camshaft inspection, I'd be pricing it as nearly run out.
FlyRvR@reddit (OP)
Been there since 1977. Flown consistently, but very little. The engine tach is from the late ‘90s.
rFlyingTower@reddit
This is a copy of the original post body for posterity:
Only 20 in the last six years, hangared, kept clean in a desert environment.
How worried should one be about cylinder/crank corrosion?
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