the fifteen million cycle problem (cam failure)

[jetdriven]

I sit here still wondering about causes of camshaft and tappet failure. It occurred to me that our camshaft has turned 15 million cycles since we bought it.  (2500 RPM x 200 hours)  I understand disuse and corrosion can wreak havoc on an engine, but this is the equivalent of 14,000 vehicle miles before the failure manifests itself.  Let your car sit, drive it a whole year, then the cam fails.  It takes that long to finally go bad? I have a hard time believing that.

 

Other airplanes sit for years or are underflown for years. I have a friend with a S35 Bonanza flew 10 hours in the ladt 5 years. Sat most of it. Another friend with a T-6 Texan (last overhaul, 1952) and a luscombe (last overhaul never, new since 1946).   This is uniquely a Lycoming 4-cylinder problem.

There has to be more to it than this.

[M016576]

Quote: jetdriven

I sit here still wondering about causes of camshaft and tappet failure. It occurred to me that our camshaft has turned 15 million cycles since we bought it.  (2500 RPM x 200 hours)  I understand disuse and corrosion can wreak havoc on an engine, but this is the equivalent of 14,000 vehicle miles before the failure manifests itself.  Let your car sit, drive it a whole year, then the cam fails.  It takes that long to finally go bad? I have a hard time believing that.

 

Other airplanes sit for years or are underflown for years. I have a friend with a S35 Bonanza flew 10 hours in the ladt 5 years. Sat most of it. Another friend with a T-6 Texan (last overhaul, 1952) and a luscombe (last overhaul never, new since 1946).   This is uniquely a Lycoming 4-cylinder problem.

There has to be more to it than this.

[201er]

+1

[johnggreen]

Byron,

I find the subject of your post interesting because of my years in the construction business and EXTENSIVE experience owning equipment of all kinds.  I saw both; from buying a lowboy truck out of the weeds and successfully running it for ten years, to taking a newly rebuilt Murphy diesel out of a Northwest crane (that had sat for ten years) and having it completely fail in the first four hours of running.  I recently bought two military surplus 5 ton dump trucks from the marshalling yard of the Marine base for use at the ranch.  They have 250 Cummins diesels, built in 1987, less than ten thousand miles on the trucks.  Sat at the marshalling yard waiting for sale for four years-the military doesn't move fast.  Changed the filters, put on new batteries, aired up the tires, and we run them almost everyday !  I have a friend (yes, I have friends) that a few years ago bought an old tractor.  The engine was frozen up.  He pulled the heads, poured Coca Cola into the frozen cylinders and the next day could turn the engine over.  Replaced the heads, fired it up, and started breaking up his garden.

Go figure.

As for the Lyc IO-360, I would first wonder if it's rate of cam failure is any different than the 540 or 720.  Same design, just more of essentially the same cylinders. Sitting here, thinking about the issue and what's different, I wonder if Aviation oil perhaps has different properties that allows the oil to drain off sooner?

Fact is, I don't know but will follow your thoughts.

Jgreen

[PTK]

I don't think it's an issue of number of run cycles necessarily. I think its an issue of accumulated time of activity vs inactivity. Lycoming SL L180B sets down definitions of an active and inactive engine along with specific preservation methods for each. Very few people follow these guidlines because it is a little inconvenient. This is why its more advantageous to buy a runout engine aircraft priced accordingly, put an engine in from the start and fly it. Just my opinion.

[Becca]

Quote: allsmiles

I don't think it's an issue of number of run cycles necessarily. I think its an issue of accumulated time of activity vs inactivity. Lycoming SL L180B sets down definitions of an active and inactive engine along with specific preservation methods for each. Very few people follow these guidlines because it is a little inconvenient. This is why its more advantageous to buy a runout engine aircraft priced accordingly, put an engine in from the start and fly it. Just my opinion.

[Piloto]

Another factor that causes these inactivity failures is where the plane is stored. A plane that is tiedown is exposed to continuos sun heat causes the oil to gradually evaporate from the cam and other engine parts leaving them exposed to the environment which is more corrosive than in a hangar. A hangared plane is much less prone to these problem.

José 

[jetdriven]

FWIW our plane sat, at the most, 5 days since we bought it.  Put 220 hours on it in ~16 months. Aeroshell W100 and Camguard since the first day.  I bought into the idea we were protected.  The evidence suggests something else.

[AndyFromCB]

My engine has eaten 3 camshafts in 3500 hours according to logbooks, first on at 1600 hours (Matituck overhauled), another one at 2400 hours and then again (Leavens overhaul) and then another at 3500 hours (Central Cylinder). It wasn't from lack of usage. Engine is 20 years old, flown on average 175 hours per year. Camguard always used as well.

I posted the pictures of the camshaft in the Bravo Forum section.

Byron, consider yourself lucky. My removal/reinstall bill is closer to 20K with the various bits and pieces that Bravo uses. Almost 12K in parts alone.

[aviatoreb]

Quote: jetdriven

Other airplanes sit for years or are underflown for years. I have a friend with a S35 Bonanza flew 10 hours in the ladt 5 years. Sat most of it. Another friend with a T-6 Texan (last overhaul, 1952) and a luscombe (last overhaul never, new since 1946).   This is uniquely a Lycoming 4-cylinder problem.

There has to be more to it than this.

[jetdriven]

Quote: Becca

This is a little divergant from the main topic, but I used to think the same way about buying a plane with a run out engine.  But now that we're in the process of putting in an engine, I don't think airplane values appropriately reflect teh cost of replacing a run out motor.  The standard "valuation" for a plane with a run out engine is $20-25k less than a new engine (variable based on the quality of the engine - e.g. factory reman vs. shop overhaul and everything in between).  We're getting what I would call one of the higher quality overhauls (e.g. factory overhaul) and its going to end up costing us all and all, about $35k and this is minimizing the labor cost by doing a great deal of the work ourselves - if we weren't doing this, my rough estimate would be a price closer to $40k.  So let's follow this thought to the logicial conclusion - say there are two identical M20J's on the market, one $70k with a run out engine and one $90k with a brand new engine, I think the brand new would be better value even though you are rolling the dice.

Two years ago we were making the same trade ourselves, and went for the midtime engine.

Anyway..

[PTK]

Also while on the subject things to consider are the habits of the pilot in the operation of the engine through the years:

were they mindful of RPM at engine start up or were they sloppy allowing a cool engine to race, did they allow time necessary for proper warm up of the engine, oil and CHT before application of full power and did they allow proper time for cool down before shut down. 

Habits are very important because their effects on the engine are cummulative.

 

 

[AndyFromCB]

Quote: aviatoreb

I hear you on that.  I am bewildered how some airplanes seemingly go for decades of disuse and keeping turning on when you kick it over and nothing bad seems to outcome.  My AP was telling me recently about a Cessna 170 from the 1960s that flies maybe 5 or 10 hrs a year that sits at a nearby grass strip airport for 9 months of the year in a roof-only hangar. Snow piles up all around it.  I don't understand why that motor hasn't just disappeared in corrosion by now.

[jetdriven]

OK, it seems there is commonality with engines overhauled around 2001 or newer, and the failures occur around 1000-1300 hours.  I will post detailed specs of ours if enough interest is given.

[201er]

RIP A3B6d 1998-2012, Overhauled by Performance Aero Engines, 1400SMOH. Ferrous metal in oil (likely cam).

[KSMooniac]

Quote: jetdriven

FWIW our plane sat, at the most, 5 days since we bought it.  Put 220 hours on it in ~16 months. Aeroshell W100 and Camguard since the first day.  I bought into the idea we were protected.  The evidence suggests something else.

[danb35]

Quote: allsmiles

did they allow proper time for cool down before shut down. 

[KSMooniac]

For the record, I'm still flying behind a 1991 factory overhaul. although I freshened the cylinders at 1650 SMOH/18 years.  ~2000 SMOH currently with no plans to tear into it.  /knocking on wood

[PTK]

Quote: danb35

There is absolutely zero reason (and not even a reasonable argument) to "cool down" on a normally-aspirated engine, and even on a turbo the idea has been pretty thoroughly debunked--the turbo is as cool as it's going to get when you touch down, and taxiing or idling just heats it back up.

[jetdriven]

Quote: KSMooniac

Unfortunately your care, operation, and use cannot undo what was done prior to your purchase.  You already posted how little it flew in the years before you bought it, and I suspect it was already going down the road of premature failure when you got it, and there was no way to back up and take a different turn...

[jetdriven]

Quote: allsmiles

There is absolutely zero reason (and not even a reasonable argument) to "cool down" on a normally-aspirated engine, and even on a turbo the idea has been pretty thoroughly debunked--the turbo is as cool as it's going to get when you touch down, and taxiing or idling just heats it back up.

[PTK]

Yes it did Byron. The consensus from everyone I've spoken with is to allow the engine to cool down at 1000 RPM for about 5 min prior to shut down. There are good reasons for this recommendation.

[Bolter]

Quote: jetdriven

Can we agree to diagree? Because we certainly disagree!

[John Pleisse]

Disuse...sunbelt humidity.

[jlunseth]

There is a company in CO, Firewall Forward, that has a camshaft STC for Lycomings, and I am pretty confident it covers J's.  They presented at the Mooney PPP in CO last year.  They provide a hollow cam with lube holes in each lobe and at the bearings, so that the camshaft is fully lubed, particularly at start up as soon as the oil pump begins to work.  Supposed to be pretty good, don't know myself I have a Cont.