0-360 engine question

[keb0]

Looking at a potential AC located in Ak to purchase; a 2000 model with 800 TTSN on the 0-360 and airframe. No known or documented damage history. Floats and wheels seasonally. One owner since new, a very conservative pilot owner. Lifelong hangar queen, appears very well maintained. Inspection and borescope scheduled. Question is, would the low frequency usage on the 23 year old engine make it likely it will not make TBO or beyond? These hours averages out to 2.9 hrs per month over the life of the engine. This was typically one flight roundtrip per month. Would you anticipate corrosion issues or significant oil leaks in near future? My last bird (0-320) made it to 2400 hrs under close scrutiny before cam wear required a rebuild, but was flown much more frequently. I plan to fly a little more than average but not prolonged hard use; 25-40 hrs per month in the summer months, little less each winter. Comments, experiences? Thanks

 

[Salty]

My Mooney's O-360 went 52 years and 2680 hours between overhauls. Was still running fine when I did the overhaul. No oil leaks.

 

[jbarrass]

How many hours in the last year?

Are there any oil samples?

 

[Dan Thomas]

Has the airplane been on saltwater? The whole airframe might have corrosion problems.

 

[brcase]

Do be careful that all AD's are properly documented. We had to do a teardown just to find out that a crankshaft AD had been complied with, it just hadn't been documented properly in the logbooks.
An expensive missing entry in the logbook.

Ours only gets flown about 30-50hrs per year between March and September, for the past 20 years we have owned it. Crank and cam were still going strong when we had it tore down about 2 years ago.

Brian

 

[keb0]

How many hours in the last year?

Are there any oil samples?

Will find out Saturday, thanks.

 

[keb0]

Do be careful that all AD's are properly documented. We had to do a teardown just to find out that a crankshaft AD had been complied with, it just hadn't been documented properly in the logbooks.
An expensive missing entry in the logbook.

Ours only gets flown about 30-50hrs per year between March and September, for the past 20 years we have owned it. Crank and cam were still going strong when we had it tore down about 2 years ago.

Brian

Good advice, thanks. I have a good IA scheduled to do the prebuy.

 

[keb0]

Has the airplane been on saltwater? The whole airframe might have corrosion problems.

Owner states absolutely no salt. Will definitely inspect for corrosion. Thanks.

 

[Hang 4]

Two things I'd look at. The duration of the flights, looking for at least 45 min or more. The second would be to ask if it was ground run between flights, if yes then a hard no. What you don't want is it to be run enough to produce water in the oil and then not enough heat to force back out.

 

[Ed Haywood]

TBO is 2000 hours or 12 years, so on paper you are already past. Nobody in GA adheres to that rule so it's a bit pedantic, but worth making the point. No matter how well the engine is treated, seals and gaskets dry out over time.

IMO life expectancy depends on how regularly it was operated. If it was actually operated 2.9 hours per month, every month, then it could be in decent shape. Conventional wisdom on PoA says aircraft needs to be flown at least 30 minutes every 30 days to boil contaminants out of the oil. That is consistent with Lycoming guidance to preserve engines that will not fly for 30 days.

Lycoming cams are not immersed in oil; they sit in open space inside the case. After each operation, the oil coating on the cam gradually runs off and dries, exposing the lobes to corrosion. If the aircraft was periodically allowed to sit for longer periods of time, say 3-6 months, or if it was regularly ground run in lieu of flight, then the cam lobes and tappets probably have corrosion. Once that process starts, the hardened surface erodes over a period of several hundred hours. Telltale sign for that is increasing quantities of ferrous dust in the oil filter. Once it breaks through to the softer metal underneath, you get flakes and chunks instead of dust, and overhaul is imminent.

Borescoping cannot reliably detect this process. The only thing that can is detailed knowledge of history such as a flight log, or inspecting the filter at oil change intervals.

If the aircraft is otherwise well cared for, then it's probably a good deal regardless. Price the engine as if it had 1500 hours, and you have a good chance of meeting expectations, and a decent chance to exceed them.

 

[Grum.Man]

The reality is, you just don't know. If the cylinders are original you can bore scope them and get a good feeling of how corrosive it's environment has been. All you can do is compare it to similar planes for sale and determine if it's a good enough value for you. If spending 30k after 100 hours sends you the creditors then I'd advise saving up a bit more money before purchasing an airplane. The engine is double it's recommended overhaul on calendar time which is no different than if it had exceeded it's tach time recommendation. No reason to pull it and have it rebuilt but certainly worth bringing up in negotiations.

 

[Flyhound]

The O-360 in my Maule only got 1,000 hours before needing a top job because the previous owner wasn't flying it enough. After replacing the cam, the bearings (yes, the case had to be split) and other parts in the engine, I only got another 1200 hours on it before finding metal in the oil filter again. I was flying 120-130 hours per year, so the plane was active. I live in the Seattle area, so lots of humidity and probably a lot of chloride ions in the air from all the salt water around here. I'd definitely want to see the engine run hard and long, followed by an oil change with the filter cut open to see if any metal was being captured. If the plane was inactive near salt water for long periods of time, I'd bet dollars to donuts that you'll find ferrous metal in the oil filter. Here's the amount of metal I found at my last oil change. I'm waiting for a rebuilt engine from LyCon and I'll be using a dehumidifier on the plane in the hangar as well as getting the tappets DLC coated, and the camshaft cryogenically treated.

 

[Dan Thomas]

Lycoming cams are not immersed in oil; they sit in open space inside the case. After each operation, the oil coating on the cam gradually runs off and dries, exposing the lobes to corrosion. If the aircraft was periodically allowed to sit for longer periods of time, say 3-6 months, or if it was regularly ground run in lieu of flight, then the cam lobes and tappets probably have corrosion. Once that process starts, the hardened surface erodes over a period of several hundred hours.

Continental cams aren't immersed in oil either. The oil level is well below it. It's just low enough to clear the con rods. The one disadvantage Lyc has over the Continental is that high placement near the top of the case, which is the coolest spot when an oil sump heater is installed and operating. Moisture in the sump evaporates and recondenses on that camshaft.

If the cylinders are original you can bore scope them and get a good feeling of how corrosive it's environment has been.

The environment is nothing compared to the water vapor blown into the case during ground-running. It condenses in there, mixes with the oil, and in the presence of catalyzing metals it forms three different acids that eat the engine. Ground-run engines have short lives. Period. I've seen too many of them. My A-65, on the other hand, sat on an airplane in a swampy area for ten years and had no corrosion when I opened it up.

 

[Ed Haywood]

Here's a really good article on camshaft and lifter corrosion and spalling, with lots of photos:

Cessna Flyer Association - Camshaft & Lifter Wear

Corrosion attacks camshafts and lifters before most other bottom-end engine parts, especially when an aircraft doesn’t fly frequently. Learn how to prevent, identify and treat common camshaft and lifter problems before they cost you! Many folks think of engine wear and tear and overall condition...

www.cessnaflyer.org

Again, not a reason to avoid buying. Just for awareness that "low time" is not preferable to "regularly flown."

 

[bnt83]

Worst lifter in a 55 year old 2000 hr engine O320E2D

 

[Dan Thomas]

I live in the Seattle area, so lots of humidity and probably a lot of chloride ions in the air from all the salt water around here.

Chlorine also comes from the oil itself. So do sulfur and nitrogen. So we get hydrochloric, sulfuric and nitric acids when moisture from ground-running mixes with that oil.

From:
https://www.azom.com/article.aspx?ArticleID=16622

Combustion By-Products​

Exhaust gases - or blowby gases - that leak past the valve guides, piston rings, and turbocharger seals into the crankcase contain particles of acids, carbon, partially burned fuels, water, lacquers, and varnish that contaminate the oil. Sulfur oxides (SOx) are common gases with sulfurous fuels (liquid fuel distillates, diesel, heavy fuel oil). Nitrous oxides (NOx) are more pronounced with natural gas (LNG, CNG, propane) fueled engines. Hydrocarbon oxidation (HCOx) will exist in differing amounts.

Acids, Varnish, and Sludge​

When the lubricating oil comes into contact with hot engine components, or if heated oil contacts the entrapped air, oxidation and decomposition take place, forming contaminants such as acids, sludge and varnish.

Air-cooled aircraft engines suffer more blowby when they're not at operating temps, and ground-running is the classic situation there.

Lycoming has this, in
https://www.lycoming.com/content/frequency-flight-and-its-affect-engine

Some operators are running the engines on the ground in an attempt to prevent rust between infrequent flights. This may harm rather than help the engine if the oil temperature is not brought up to approximately 165˚ F because water and acids from combustion will accumulate in the engine oil. The one best way to get oil temperature to 165˚ F is to fly the aircraft. During the flight, the oil normally gets hot enough to vaporize the water and most acids and eliminate them from the oil. If the engine is merely ground run, the water accumulated in the oil will gradually turn to acid, which is also undesirable. Prolonged ground running in an attempt to bring oil temperature up is not recommended because of inadequate cooling that may result in hot spots in the cylinders, baked and deteriorated ignition harness and brittle oil seals which cause oil leaks.

 

[keb0]

Thanks everyone, there's a lot of good information being passed around. I appreciate it. Have a competent IA scheduled to check out the plane so it will be well scrutinized. Hopefully, he can get a good look at least some of the cam lobes. Cheers!

 

[keb0]

How many hours in the last year?

Are there any oil samples?

Around 50, don't know yet, inspection has not been completed yet. Good question. Thanks

 

[keb0]

Chlorine also comes from the oil itself. So do sulfur and nitrogen. So we get hydrochloric, sulfuric and nitric acids when moisture from ground-running mixes with that oil.

From:
https://www.azom.com/article.aspx?ArticleID=16622

Combustion By-Products​

Exhaust gases - or blowby gases - that leak past the valve guides, piston rings, and turbocharger seals into the crankcase contain particles of acids, carbon, partially burned fuels, water, lacquers, and varnish that contaminate the oil. Sulfur oxides (SOx) are common gases with sulfurous fuels (liquid fuel distillates, diesel, heavy fuel oil). Nitrous oxides (NOx) are more pronounced with natural gas (LNG, CNG, propane) fueled engines. Hydrocarbon oxidation (HCOx) will exist in differing amounts.

Acids, Varnish, and Sludge​

When the lubricating oil comes into contact with hot engine components, or if heated oil contacts the entrapped air, oxidation and decomposition take place, forming contaminants such as acids, sludge and varnish.

Air-cooled aircraft engines suffer more blowby when they're not at operating temps, and ground-running is the classic situation there.

Lycoming has this, in
https://www.lycoming.com/content/frequency-flight-and-its-affect-engine

Some operators are running the engines on the ground in an attempt to prevent rust between infrequent flights. This may harm rather than help the engine if the oil temperature is not brought up to approximately 165˚ F because water and acids from combustion will accumulate in the engine oil. The one best way to get oil temperature to 165˚ F is to fly the aircraft. During the flight, the oil normally gets hot enough to vaporize the water and most acids and eliminate them from the oil. If the engine is merely ground run, the water accumulated in the oil will gradually turn to acid, which is also undesirable. Prolonged ground running in an attempt to bring oil temperature up is not recommended because of inadequate cooling that may result in hot spots in the cylinders, baked and deteriorated ignition harness and brittle oil seals which cause oil leaks.

Good info. Have heard this basic info in various circles over the past 40 yrs or so, but see a few tidbits in there I don't remember. Thanks.

 

[keb0]

Worst lifter in a 55 year old 2000 hr engine O320E2D

View attachment 124515

That's a success story! I did quite a bit of flying down your neck of the woods back in the 80's-90's. CFI at the flight school at Millard Field, Omaha, then cable patrol, VFR 135, IFR Multi 135 and moved over to Eppley for Corporate, 135, Air Ambulance, and Express Mail feeder for the USPS in Aero Commanders. The Airline industry was saturated with Military Pilots getting out of the service positions, so times were tough for young pilots. Went North to Alaska in 93. It's been an adventure, and more to come. Thanks for the info. Cornhusker.

 

[murphey]

My Mooney's O-360 went 52 years and 2680 hours between overhauls. Was still running fine when I did the overhaul. No oil leaks.

Mine went 50 years, 3200 hrs and only did the overhaul due to a prop strike. Crankshaft was still good, too. Got all new cylinders, hoses and the oil cooler.

And a prop.

 

[bnt83]

That's a success story! I did quite a bit of flying down your neck of the woods back in the 80's-90's. CFI at the flight school at Millard Field, Omaha, then cable patrol, VFR 135, IFR Multi 135 and moved over to Eppley for Corporate, 135, Air Ambulance, and Express Mail feeder for the USPS in Aero Commanders. The Airline industry was saturated with Military Pilots getting out of the service positions, so times were tough for young pilots. Went North to Alaska in 93. It's been an adventure, and more to come. Thanks for the info. Cornhusker.

I'm from South Dakota but have been a transplant coming up on 20 years. I really enjoy flying out of Lincoln. It's just big enough to be neat and sometimes its busy enough to make it really fun. Had around twelve V22 Osprey landing once when I was doing touch & goes.

A local older guy says it's the angle valve engines that really eat camshafts and lifters. Mine would prob have lasted another 5 - 10 years IMHO.

That being said none of them are immune, it's just luck IMHO. But the engine that lifter came out of was 2000 total time since new and about 55 years old. The crankcase and crankshaft passed inspection/repaired and are going back in with new camshaft kit and all new cylinder kits (on a Cessna 177). No special engine preservation action taken, and no cam guard used. Just plain old Phillips 20w-50 X-Country oil changes about every 35 hours for the last 20 years.

 

[Stewartb]

Anchorage area? What type is the plane?

Hangars don't help with occasional use corrosion but it's a total crapshoot why some engines rust and some don't. You'll need to accept that there's always a risk when buying a plane. Roll the dice or don't. There's no sure answer. I bought an 0-320 from a friend at Birchwood who removed it to upgrade to an 0-360. His plane was familiar to me and it ran fine, and was hangared. When I pulled a cylinder out of curiosity it was obvious that the cam was total junk. I had to do a major overhaul with lots of new parts. You just never know.

 

[keb0]

The reality is, you just don't know. If the cylinders are original you can bore scope them and get a good feeling of how corrosive it's environment has been. All you can do is compare it to similar planes for sale and determine if it's a good enough value for you. If spending 30k after 100 hours sends you the creditors then I'd advise saving up a bit more money before purchasing an airplane. The engine is double it's recommended overhaul on calendar time which is no different than if it had exceeded it's tach time recommendation. No reason to pull it and have it rebuilt but certainly worth bringing up in negotiations.

Agree with you on these points, thanks.

 

[keb0]

Anchorage area? What type is the plane?

Hangars don't help with occasional use corrosion but it's a total crapshoot why some engines rust and some don't. You'll need to accept that there's always a risk when buying a plane. Roll the dice or don't. There's no sure answer. I bought an 0-320 from a friend at Birchwood who removed it to upgrade to an 0-360. His plane was familiar to me and it ran fine, and was hangared. When I pulled a cylinder out of curiosity it was obvious that the cam was total junk. I had to do a major overhaul with lots of new parts. You just never know.

Yes Sir, Anc area. Agree that it's all really just a crapshoot, and after a thorough inspection, you make an educated choice to roll the dice or not. Most things in life involve the element of risk, keeps it interesting I reckon. Thanks for the comments.

 

[keb0]

Made it through the Pre buy, the I.A. did a great job, and identified a couple failed components. The owner has been fantastic and it appears this will result in a satisfactory purchase. Pretty stoked. Thanks again for all the help guys.

 

[keb0]

 

[fabricgator]

Nice!