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Engine making metal...

AlexPeterson

AlexPeterson

Well Known Member
I was just thinking about the good luck I've had with my engine for almost 10 years, with no problems whatsoever save for a fuel pump needing replacement.

Well, I was finishing an oil change (1270 hours), and dutifully cut open the oil filter. It is quite startling to see little shiny flecks in there! I brought the fan-fold filter home for further analysis. I have a nice stereo microscope at home, which came in handy. What I found were little flakes, mostly iron, around .005" to .008" in size. I saw around 6 to 12 pieces per pleat. Their thickness is extremely thin, probably 50 - 250 millionths of an inch if I had to guess. There were a few I found that were in the .020" to .030" size range, and a few of the smaller ones were non-ferrous.

With only reading glasses in sunlight, I probably would have counted about 30 to 50 pieces. Microscopes must be used with caution...

I've spoken with one mechanic (before I knew if the pieces were magnetic, size, shape, etc.) who suggested cam if they were little thin pieces and ferrous.

The Lycoming Flyer Maintenance guide suggests some steps as well, such as running for a half hour and checking the filter again, followed by 2 hours' flight time, and again looking. However, I'm not too interested in flying it...

Next steps:

1. Pull screen to look for anything that might be larger than the holes in it.
2. Boroscope everywhere possible
3. Get some money
4. I regularly do oil analyses, and it will be interesting to see the results of this one.

All seasoned and reasoned suggestions welcomed! I'll keep progress posted.
 
Before you get that sick in the stomach feeling I had when I pulled my oil screen and had LOTS of metal, get advice from people smarter than me whether what you are seeing is abnormal or normal.

Your item #3 may not be needed except for your next trip.
 
Oil analysis

What has been the trend with your oil analysis? I use Blackstone labs and they are fantastic in their data and demonstrating trends.

I'd have the oil checked before panicking. Plenty of time for that:eek:
 
What you're describing is normal. If they didn't put a little bit of metal in the filter, they'd never wear out.
 
Check the sump screen just to be sure that no really big pieces are being generated... better safe than sorry here...
 
AlexPeterson said:
What I found were little flakes, mostly iron, around .005" to .008" in size. I saw around 6 to 12 pieces per pleat. Their thickness is extremely thin, probably 50 - 250 millionths of an inch if I had to guess. There were a few I found that were in the .020" to .030" size range, and a few of the smaller ones were non-ferrous.
Click to expand...

My compliments Alex....rarely do we read such an accurate description.

The Lycoming Flyer Maintenance guide suggests some steps....
Click to expand...

Most of us have read the Flyer, John Schwaner's work, some Kas Thomas, some others....but where is the really complete reference on cut filter examination?
 
Some pictures

The rod in one picture is .012" diameter, to set the scale. All the pieces are very thin flakes, for lack of a better word. The magnet holding the parts is .125" in diameter, and it is being held by a small screwdriver. This might represent 5% of what's in the filter?

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A couple replies to posts:

As I mentioned in the original post, I will be checking the screen. Also, if this metal is normal, I've not seen it in 1200+ hours in this motor. I'm told that my oil analyses typically show about half the metal contaminants that one would expect, and they have been stable over the last ten years. It will be interesting to see this one's results, although not particularly helpful (don't need it to know something's going on...)
 
AlexPeterson said:
3. Get some money

All seasoned and reasoned suggestions welcomed! I'll keep progress posted.
Click to expand...

I love this one. Simple, accurate and true. It was good to see you the other day Alex. Good luck with your engine. Its always better to discover these types of problems on the ground rather than in the air.
 
Alex,

All I can say is WOW!

The stuff has been confirmed to be of iron or steel so by deduction it is coming from iron or steel parts. Maybe valves, rings or crank shaft.

I'd be on the phone with Allen at BPA.

dd
 
I don't agree that this is normal. It's not. If that stuff is mostly ferrous I'm thinkin' cam/lifter. Valve tip shavings are usually larger. Bunches of aluminum flakes are often piston pin plugs going south. As an aside, I've seen where oil analysis showed fairly normal with lots of large metal visible in the filter. I think the mass-spec on analysis tends to miss large metal and only detects the fines. If I found that sort of stuff in a filter I'd clean out thoroughly, run some more (in pattern), and check again. Then I'd probably find more metal, rip a jug and start looking at lifter faces. My first boss (ex B-17 driver) once told me "engines don't heal themselves". I've never forgotten it. Of course, a former bandmates father also once told me "only retards smoke cigars". I can't forget that either.
 
If this is abnormal metal, why even run a few hours to check a new filter?

Start the physical checks.
 
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One cold start could produce this amount of metal in the filter. This isn't anything to cry wolf about or start opening up the motor over. I am an A&P and I've literally looked at hundreds of filters cut open over the past 20 years. I would check the oil filter again in 10 hours and go from there. And you should be checking the screen on every oil change.
 
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That much, though, Bob? Alex said what was on the magnet was maybe 5% of what he found in the filter. So the filter held 20x that amount. Just seems like a lot of metal. I can wrap my mind around the amount shown on the magnet being normal, but not 20 times that much. Then again I'm no A&P though.

Could is be lifter spalling, maybe?
 
Yes. I've seen much worse!

If it keeps on making more metal, then that's when you deduce there's a real problem. In other words, a trend is what matters.

In reality this is not much different than an engine with a low cylinder. You go and fly it, then check it again.

Some people believe in oil analysis. I certainly don't. I've overhauled engines that had major internal problems where the last oil analysis said things were rosy.

One other thing. I've seen a lot of people look at filters while there's oil dripping off of them. Please don't do that. Cut the filter element in two, wrap the element in a paper towel, and squeeze all of the oil out of the elements in a vise.
 
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Thanks, Bob. I've read so much about Lycoming lifter spalling that I'm probably a little over-paranoid about it. Probably because I deal with a lot of late 70's Skyhawks with the H series O-320's. Off topic, I know, but how bad can a lifter get before it starts to chew away at the cam?
 
Cam lobe wear - question for Rocket Bob

Bob -

Is there a pattern to cam lobe wear?

1. There are two lobes that operate two intake valves each. It seems like they might wear first.

However,

2. Exhaust valves have to open against cylinder pressure, so their contact loading must be higher.

3. How do you check potential lobe wear? Remove rocker covers and turn over engine? It seems like an automotive cranking type compression test might also work.

I had a 2025 hr. engine that had good leak-down, but was obviously power deficient. either that or the trees at the end of the runway were really growing rapidly ;-) conclusion was worn cam lobes. The replacement engine was a BIG improvement.

LarryT
 
To check for cam lobe wear you can pull the valve covers and put a 1" travel dial indicator on the rocker arms. Then slowly pull the prop. around to get a reading.

Steve
 
rocketbob said:
The only good way to check for cam and tappet body wear is to pull a cylinder and have a look.
Click to expand...

Checking with an indicator is only an initial test, easily done for a suspected problem before tearing in to the engine. Certainly a visual check of the cam would be next.

Steve
 
Zero4Zulu said:
Checking with an indicator is only an initial test, easily done for a suspected problem before tearing in to the engine. Certainly a visual check of the cam would be next.

Steve
Click to expand...

I think the point is: even if a dial indicator test doesn't show anything, you need to visually inspect the cam for damage. Roughness on a cam won't show up on a dial indicator. If a dial indicator shows worn lobes, they have been bad for a while and are on their last legs.
 
my guess.....

...is cam/lifter too. I also own and operate a Duke, which is famous for cam/lifter issues. those flakes look exactly what the lifters produce when they start wearing out.
 
john.schwaner said:
The picture shows particles from a camshaft follower. This is not a wear particle but produced by metal fatigue.
Click to expand...

John... that part is surface hardened isn't it?

If so, I would presume that a fatigue of the surface is the start of a rapid deterioration of the follower.

Is that correct?
 
lifter spalling

This is what a lifter looks like when the surface hardening has been compromised:

overhaul-6.jpg


And the rounded off cam lobe:

overhaul-13.jpg
 
surface hardened - yes, principle stress occurs just below the surface - same as a pothole in the road- crack starts just below the surface until a thin chip pops out. The chunks aren't detected by an oil analysis lab until late in the game as they are too large, get filtered out, settle to the bottom of the sump or sample jar.

Years ago one used to see a small hardness mark (quality-control test) on every tappet purchased - 100% hardness tested. I notice recently that I purchased some that did not have the hardness mark - I'm out of that business now so I might be mistaken but possibly some cost savings in the QC department.

One quick test if you have a cylinder removed from the engine is to reach in with your hand and drag your fingernail across the tappet face. If your fingernail "catches' then you have some tappet spalling.

Now what to do? Start the budget process.

As time goes on and the tappet and lobe surfaces get ground down the engine will produce less power - but remain smooth. Typically, an engine in this condition will sail right pass a pre-purchase or annual without detection. A static rpm check will be low.

Any bits that get past the oil filter (bypass mode activated on cold mornings with 100W oil) get filtered by the connecting rod bearings where they embed themselves into the babbitt and then scratch the crankshaft journal.

--but then again I could be wrong -- pictures are tough to analyze as nothing beats the real thing.
 
john.schwaner said:
The picture shows particles from a camshaft follower. This is not a wear particle but produced by metal fatigue.
Click to expand...

How do you know this? It could be from cylinder scoring or scuffing. Broken ring perhaps... I've seen a magneto bearing failure lead up to ferrous material in the filter.
 
Looks like

lifter and or cam material to me (the shiney flakes), but like Rocket said, you don't know until you really know. If the decision to moniter and continue to run, then please make shaking the prop forward and aft part of the preflight. If that clearance goes away, it is because it is filled with metal. That is a show stopper.
 
Update

First, thanks for all the feedback.

Second, some results so far:

Jugs #1 and #3 were removed to allow inspection of the cam and followers.

Some possible distress from contact pressure stress can be seen in these pictures. It wasn't as evident when looking live as it is now when looking at these pictures. I was not able to feel anything with a fingernail. An A&P friend of mine will look in the next day or two, and we'll make a decision. Clearly not bad, and it might go many hundreds of hours. But, it won't go away by itself.

P6183202%252520cropped.JPG


P6183203%252520cropped.JPG


Additionally, a wrist pin button show some excessive wear on #1:

N66AP%252520jug%2525201%252520plugs.JPG


The two cylinders removed show no wear whatsoever from the rings, with just a little scoring on the pistons in the thrust side. Exhaust valve looks uniformly brown.

More to follow in the next days.
 
Those are the old-style piston pin plugs. Newer ones are pressed on the wrist pin. Normally the pins will get locked into the pistons with carbon deposits, so the newer style pressed-on pin plugs don't float around and wear.

If you replace these pin plugs make sure they're of the same material as the originals so that you don't upset the balance of the engine.

Like I mentioned earlier I did not think disassembly was warranted based on the pictures you posted, but hopefully folks see this thread as a lesson learned on the fact that its OK to see a little bit of metal in the filter once in a while. A trend is what matters.
 
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Update

Sunday my favorite A&P stopped by to have a look. With better lighting and angles, we could see and easily feel pitting on several cam lobes. It looks like classic contact stress fatigue as outlined by another in an earlier post. The followers are indeed roughened up by the damage as well. He was surprised by the amount of glitter in the filter.

Could this engine have been safely run for a few hundred more hours? Probably, but no way to know for sure. That cam was not about to mend itself. Bob is right about establishing trends, but my trend was 1300 hours with no metal at all in the filter, then a bunch all at once. I have no interest in flying along, wondering what's going on up front for the next few hundred hours. Each will make their own decisions here, none are wrong.

We'll tear down and replace/recondition parts as necessary. It is interesting that almost all parts in the engine were new 10 years/1300 hours ago, except the cam! Don't ask, I don't know.

I'll write more once it is disassembled and inspected.
 
Alex, thanks for the update. When I first saw the photo's of the metal flakes, my first thought was cam or lifter spalling. Good catch, and I wholeheartedly agree with your decision to take care of the problem(s) now. That's what I'd do.

All my best, Joe.
 
Anyone seen something like this?

Tim disassembled the engine, and found some interesting things.

Cam - not too bad, but we'll replace
Followers - broadly pitted, and will be reman'd
Crankshaft gear - see pictures.

Picture%25252048.jpg


Picture%25252047.jpg


The pinion which is driven by this gear appears to be fine. One has to question the hardness of this gear. I plan to get a hardness measurement.

There would likely have been an unplanned landing at some point from this gear. What won't be known is over how long a period this wear was occurring. If it was the source of the metal in the oil filter, it happened only very recently.

Otherwise, the engine looks good for 1300 hours. We'll essentially do a lower end on the engine. Cylinders appear in great shape, and we haven't decided on what, if anything, we'll do on them at this point.
 
Wow, that's a new one for me too. That's a ton of wear. They usually last many thousands of hours. Does the finish also look funny to the rest of you guys?
 
That is the worst Lycoming crank gear I have ever seen. I have never seen wear like that...ever.... or anything close to that, in looking at thousands of gears in my lifetime.
Is there any identification as to source, manufacturers part number etc.? If so you might consider doing an M and D report to the FAA. That is really a total engine failure waiting to happen.
In the picture the finish on the gear almost looks like sintered iron. Doesn't look normal and the wear is beyond belief for a certified part with 1/2 life on it.
I would highly suspect a counterfeit or unapproved part.
Good Luck,
Mahlon
 
Bogus part crossed my mind too, but who would bother to make a bogus crank gear? Maybe someone put an old pair of oil pump gears on there (kidding).
 
hardness

I showed this to an engineering professor who teaches mechanics of materials. She suggested that the gear may have not been appropriately case-hardened during manufacture. The distorted/splintery areas at the edge of the indentations suggest ductility. The fact that the mating pinion gear is OK indicates that it is harder than the crankshaft gear.

Getting the hardness tested seems like a good idea.
 
Wow

Alex,
Good catch!!

I always open up my oil filter at every oil change. It's a messy job and once or twice I actually thought about not going to the trouble.

I'll never think about not checking it again!

Mark
 
Hey Alex, just for completeness, can you tell us the history on the engine? You said that almost all the parts were new (except the cam) 10 years/1300 hours ago - does that mean it was a kit engine, or did it come from a shop, or did you buy a field overhaul? Just curious about the background with those remarkable gear pictures!

Paul
 
I don't see how that much wear could have occurred on the crank gear and all of it in between one oil/filter change without completely filling the filter with metal shavings.

As I recall in the crankshaft bolt SB Lycoming says that carburized gears are to be discarded. So it would be interesting to see if this was one of these.
 
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Look to see when the oil pump AD was done........ They would have inspected this gear at the same time the accessory case was off.
 
rocketbob said:
I don't see how that much wear could have occurred on the crank gear and all of it in between one oil/filter change without completely filling the filter with metal shavings.
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I agree it seems hard to believe that this could have occurred in an oil change interval. I guess anything is possible but it sure sees unlikely. If the gear was soft it should have been wearing from the get go. If improperly hardened..not deep enough.... if that is possible.... then once you were past the hardness layer it would probably go pretty fast. My experience with things that were improperly hardened is they wear excessively immediately and make a lot of metal in very short order. So if it was that kind of issue, then maybe it could wear like that in such a short span if the metal was like butter under a very thin hardness layer.
He was also doing oil analysis.. There should have been significant evidence of this in prior filters and analysis if it was wearing all along. But, that wasn't the case.
Any way, very unusual and very dangerous! It would be interesting to know where that gear came from. If from a reputable source, it might be a sign of things to come as it is unusual to get one bad gear in a batch. Normally, the whole batch or even multiple batches are affected by a process failure.
Good Luck,
Mahlon
“The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information responsibly and at your own risk."
 
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Some answers:

1. Engine built by large shop commonly used by RV'ers. Mixed new/used parts. Casings used, new most everything else, recon cam.
2. Crank gear being traced now
3. Direct crank pickup dual Lightspeeds, although first 750 hours had Lasar Slicks.
4. I don't have the book in front of me, but all AD's prior to engine build done (1999 or so)
5. Oil analysis - normal and no trends of any sort, including this most recent one. (please start a new thread if you have comments about oil analyses)

I will do hardness test on the crummy gear, as well as the cam gear (which we will replace with integral type) for comparison. The cam gear looks normal. Recommendations on shops to do accessory case mod for integral gear welcomed.

We are doing a bottom end on it, and I haven't decided on what, if anything, to do with the jugs yet.

Thanks for all replies.
 
AlexPeterson said:
Some answers:
3. Direct crank pickup dual Lightspeeds, although first 750 hours had Lasar Slicks.
Click to expand...

I don't think the root cause is a gear manufacturing/hardness problem. Since you don't have mags installed the right mag idler gear could be ringing on every power pulse and beating the crankshaft gear to death. I would remove the idler gear on the right side since it no longer serves a purpose. The damage to the gear appears to be consistent with this sort of thing and maybe that's why there's no metal being shed by the gear. Essentially the crankshaft gear could be getting shot peened to death. Which would explain the lack of metal in the filter.

Gear ringing is a very real phenomena on the 540's, and this is why EI magneto hole pickups don't last on those engines since there has to be a 3:1 gear reduction to get back to 1:1 to the crankshaft rotation...the ringing beats the small gear reduction drive to death. This is why these engines have rubber couplings for the mags.
 
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Bob may be on to something, would also explain the amount of damage to the back side or the gear teeth.
 
rocketbob said:
I don't think the root cause is a gear manufacturing/hardness problem. Since you don't have mags installed the right mag idler gear could be ringing on every power pulse and beating the crankshaft gear to death. I would remove the idler gear on the right side since it no longer serves a purpose. The damage to the gear appears to be consistent with this sort of thing and maybe that's why there's no metal being shed by the gear. Essentially the crankshaft gear could be getting shot peened to death. Which would explain the lack of metal in the filter.

Gear ringing is a very real phenomena on the 540's, and this is why EI magneto hole pickups don't last on those engines since there has to be a 3:1 gear reduction to get back to 1:1 to the crankshaft rotation...the ringing beats the small gear reduction drive to death. This is why these engines have rubber couplings for the mags.
Click to expand...

Could certainly be, I wondered about the back side of the teeth also. In fact, I wondered about that pulsing/ringing/resonance problem when I spun a mag by hand. They must put a lot of torque pulses back into the gears.

Perhaps interestingly, I had two mechanical failures of the Lasar left mag, both in flight and both were some sort of internal shaft failure unique to the Lasar magneto. I learned that I was not alone in this. Perhaps the problem with my gear stems from some sort of torsional resonance that existed uniquely with the Lasar system. I had also heard that there was a redesign of the shaft underway (might have been about 5 years ago now).

If the problem is with the "unused" gear, there will be a lot of these showing up, as many RV's have nothing in the mag holes.
 
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