How will It end? (old engines)

Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
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Dave Taylor
So more and more people are running engines past TBO it seems; I wanted to poll the experiences of the group to find out what the most likely symptom was, of a failing engine.
Especially with regards to bottom end failure - not cylinders, as they are to me not really a sign of engine end-of-life.

We've all heard of lot of predictions and suppositions about what a person might expect, "making metal", "high oil consumption", "not making power", "internal component failure", etc etc (add yours supposition here if you must)

But if we were to accumulate data it would be actual experiences, not predictions.

Have you had an engine (or been closely involved with an engine) which ran past TBO and then failed, or was removed from service because of end-of-life symptoms? What was/were the symptom(s)?

Not saying we don't want to hear your hypotheticals and other thoughts on the topic, but I was truly looking for first- or maybe second-hand experiences with the above paragraph.

I'd like to list these actual, real-life observed symptoms for failing old engines in a list:
ie (this is merely an example of what I think a final list would look like)

1-45% most likely is spun or seized a main bearing, eng would not start or run properly
2-20% second most likely is could not maintain oil pressure
3-10% third by likelihood was case crack noted
4th-5% metal in filter
5th 5% loss of prop control due to metal in gov screen
6th 5%cam lobe failure, cylinder would not fire
7th 2% no symptoms but multiple accessory/cylinder failures forced the issue

Maybe we don't have access to enough data, but I thought I'd try.

Sort of like the medics do with older people! We like to know how we are going to 'go'!
 
:popcorn:
 
Actually that's me training to live on a popcorn diet, as I watch my mechanic transfer my entire net worth to his account keeping the Aztec flying. When the engines are done, I'll probably be done. :(

But I still want to know how they are most likely to fail, so appreciate you for starting this thread. :cool:
 
I bought my Cherokee with 2000 hours on both the airframe and engine. Some people like to refurb old muscle cars. For me I prefer airplanes, so I found a good low time airframe, that had not been abused by students and renters, that I could start with. I knew I would eventually have to overhaul the engine. It turned out that I was able to refurb the entire airplane (except paint job) before touchng the engine. I had 2308 on the tach when we pulled the engine. I was starting to have low compression issues in two of the cylinders. I bought four new Lycoming cylinder kits and sent the new cylinders and engine to Triad in Burlington NC for a major overhaul. I saved the paint job to last to ensure the paint would not be damaged while performing the other refurb work. I now have 137 hours on the new engine.
http://www.hhtriad.com/engine/
 

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Lemme go out on a limb.....the first signs that warrant an overhaul are low oil pressure and or high metals in the oil analysis....and maybe a leaky/cracked crank case.

Low compressions can be fixed with new or OH'd cylinders. crank shafts can go multiple OHs, cams can go an OH or two,....and most of the OH is an "inspection" process not a parts replacement regiment.
 
MickYoumans said:
I bought my Cherokee with 2000 hours on both the airframe and engine. Some people like to refurb old muscle cars. For me I prefer airplanes, so I found a good low time airframe, that had not been abused by students and renters, that I could start with. I knew I would eventually have to overhaul the engine. It turned out that I was able to refurb the entire airplane (except paint job) before touchng the engine. I had 2308 on the tach when we pulled the engine. I was starting to have low compression issues in two of the cylinders. I bought four new Lycoming cylinder kits and sent the new cylinders and engine to Triad in Burlington NC for a major overhaul. I saved the paint job to last to ensure the paint would not be damaged while performing the other refurb work. I now have 137 hours on the new engine.
http://www.hhtriad.com/engine/
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So no information that fits my request? Rats. Will keep looking. Thank you.
 
Checkout_my_Six said:
Lemme go out on a limb.....the first signs that warrant an overhaul are low oil pressure and or high metals in the oil analysis....and maybe a leaky/cracked crank case.

Low compressions can be fixed with new or OH'd cylinders. crank shafts can go multiple OHs, cams can go an OH or two,....and most of the OH is an "inspection" process not a parts replacement regiment.
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So no actual experience with this question, from which I could make a data point? Thank you.
 
Let'sgoflying! said:
Not saying we don't want to hear your hypotheticals and other thoughts on the topic, but I was truly looking for first- or maybe second-hand experiences with the above paragraph.
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The above is what I am after. I realize the post is kinda long to read in entirety so I will repost the important part. Thanks all.
 
Let'sgoflying! said:
So no information that fits my request? Rats. Will keep looking. Thank you.
Click to expand...
My information did address your request. Maybe it was not the response you were wanting, but I did tell you my first indication of problems. My first indication was low compressions. Does it make any sense to perform just a top overhaul on a 2300 hour engine? I sure didn't think so. Once Triad got into the engine they found additional parts that had to be replaced including either the cam or crank shaft that had worn beyond the allowable specifications. I can't remember which one it was now. The bearings were replaced along with worn gears among other things. There is a reason there is a 2000 hour TBO. Stuff wears out. Does that mean you can't get some life beyond 2000 hrs? Of course not, but at the first sign of problems after 2000 hrs, even if it is just compressions, I think you would be wise to overhaul that baby.
 
Start burning oil past the rings, exhaust seals going, all evidenced by lower compression and oil burn

Bearings starting to go out, as seen in the oil filter.

Normally it's not a 0-60 thing.

This pilot will end up overhauling @ TBO, mostly because I can't leave things alone, and it's a good excuse to 550 my 520 lol, that's said I got a looooong time before I hit TBO with my yearly hours put on my personal plane.
 
Many times the owner is talked into overhauling by the mechanic that warns of loosing parts that would be rare to find. Such as the 0-300-A crank shafts, if you run to failure and ruin the crank. you are going to be required to up-grade the engine. Many of the 0-300 cranks are already at minimum size, If you know that your's is, then there is no risk in loosing it, and you should run it until it has a problem.
Our Warner engine operators are now disassembling their Warners inspecting them and cleaning the old parts re-fitting as required simply to prevent a failure that will ruin parts that can't be found anywhere.
 
GlennAB1 said:
Increased oil temperature a short while before something bad happens.
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Wouldn't you also see a increase in average CHTs, different mixture setting to EGTs, different average oil pressure, too?

One of the reasons "in the green" drives me up the wall, even if something is in the green, if it's not where it normally is, not in that instruments normal "happy place", it's basically out of the green as far as I am normally concerned, atleast until it's looked at and I know why it is reading different compared to how it normally reads.
 
I'm at 600 hours over and running strong. Good thread. I'm looking at oil pressure and metal in the oil, but I really have no idea when I'm going to do it.
 
I would guess increased oil consumption should be on your list. If bearings are going, you're going to burn more oil.
 
Salty said:
I would guess increased oil consumption should be on your list. If bearings are going, you're going to burn more oil.
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I guess I need to understand this....how is crank bearing wear affecting oil consumption?
 
Salty said:
I would guess increased oil consumption should be on your list. If bearings are going, you're going to burn more oil.
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I think I'm wrong. It's just going to be lower oil pressure.
 
I had cam spalling on an io360, first symptom was cyl not firing when on short final, and then not firing after engine warmed up.

Lyc crankshaft ad was due soon so I got lots of parts cheap and an economical overhaul.


Sent from my iPhone using Tapatalk
 
1,999.6 SMOH, found low cranking compression on cyl #2. Pulled the valve covers and found very low valve lift. Differential compression numbers were fine, still made full static RPM, only a tiny bit of metal (5-6 flakes) in the filter. #2 Cam lobe was completely rounded off, lifters all spalled. The cam was on it's second run, total 4000 hrs in service.

p8x12.jpg
 
Let'sgoflying! said:
So more and more people are running engines past TBO it seems
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What do you consider running past TBO? Past by engine hours or by calendar time?

Nearly every engine I work on is past TBO by calendar time but not over by engine hours. I can count on one hand the number of engines I've overhauled so far that have made it to or past the recommended TBO hours. Most of those engines that didn't make it were Lycomings too, which everyone seems to believe are a more rugged engine than a Continental. My experience leads me to believe the opposite is more true.

The reasons for my overhauls have mainly been making metal due to either bearing or cam failure, but there have been a couple of cracked cases and one or two engines that were just old and leaking or burning a lot of oil.

In my opinion, do not delude yourself by thinking that every engine will make TBO or go beyond it. Some will and some won't. Overhaul on condition, whether that engine has 50 hours, 500 hours, or 5000 hours. You or your mechanic will know when it is time to overhaul, engines generally give plenty of warning signs before they give up completely.
 
Checkout_my_Six said:
I guess I need to understand this....how is crank bearing wear affecting oil consumption?
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They will place more oil on the cylinder walls than the rings are capable of removing.
 
I watched an IO520 disassembled for overhaul; it looked pretty much new inside, and when the A&P (at owner's request) measured the tolerances. It measured, in every value, to new-engine tolerances. The A&P (a very high-profile and well-respected one) said that, if it had been a prop strike inspection, he'd have said, "put it together and fly another thousand hours."

It had 2,880 hours on the bottom end.
 
slacktide said:
1,999.6 SMOH, found low cranking compression on cyl #2. Pulled the valve covers and found very low valve lift. Differential compression numbers were fine, still made full static RPM, only a tiny bit of metal (5-6 flakes) in the filter. #2 Cam lobe was completely rounded off, lifters all spalled. The cam was on it's second run, total 4000 hrs in service.
Click to expand...

Could you let us know engine model please? And when it was torn down where did they find the rest of the metal lodged?
 
My O-300D started losing power intermittently. During cruise it would sometimes drop about 100 rpm for no good reason. Eventually it got to the point that I was afraid to carry passengers on warm days due to anemic climb rate. Measurement of cam lift at the push rods showed two with about 1/4" and all the others about 3/8". Upon teardown the cam was found to have one badly worn lobe (shared between #5EX and #6IN IIRC) plus two lifters were severely spalled. About 3600hrs TT and 1800hrs since previous OH on an 1800hr TBO engine. Cam was original per the logs, and a few lifters had been replaced in the previous OH. New cam and all new lifters and she's been OK since.
 
Although not strictly answering your question, Mike Busch looked at this a number of years ago. Although the NTSB data base at that time included few failures past TBO (likely because few were pushing past TBO then), half of those no cause could be determined; but (and here' s the interesting part) of those where the cause could be determined a great majority were maintenance induced failures - due to something someone had recently done to the engine. Refer you to Mike Busch's book Manifesto for details and discussion.
 
GRG55 said:
Could you let us know engine model please? And when it was torn down where did they find the rest of the metal lodged?
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O-360-A4K, but this type of failure can affect all Lycoming horizontally opposed engines. Google for "Lycoming lifter spalling". Shipped the engine off to Ly-Con for the OH, no further info on the teardown.
 
Let'sgoflying! said:
You have seen an engine fail by popcorn contamination. Thanks for that data point, I will add it.
Click to expand...

Another data point to add, I saw an engine that quit running due to peanut contamination.

Rebuilt carburetor installed, engine quit a couple minutes after startup and would not start again.

A deep and lengthy 5 minute visual investigation of the carburetor show a number of packing "peanuts" in the throat of the carb. A quick clean out and the engine runs again...:D

A mechanic oversight, I know. It was at an airplane mechanic school, so everyone learned to look for peanuts....o_O
 
I have a couple of experiences:

#1: Lycoming O-320-D2J (Cessna 172P) at the Osan Aero Club, ROK: ~1200SMOH (New Limits) by signature engines, burned piston ring, subsequent piston failure caused metal contamination thru entire engine. (Lycoming granted NO core credit)
#2: Lycoming O-320-D2J (Cessna 172P- different aircraft) at the Osan Aero Club, ROK: ~800SMOH (New Limits) by signature engines, rings & piston failure, metal contamination thru entire engine. I was flying it when it failed, evidenced by rapidly climbing oil temperature. (Lycoming granted NO core credit)
1237061_597372053639048_1385257039_n.jpg

#3: Lycoming O-320 D2J (Cessna 172P- different aircraft) at the Osan Aero Club, ROK: ~UNK SMOH (New Limits) by signature engines, cam/lifter spalled & failure, metal contamination thru entire engine. Wouldn't meet minimum static RPM limits (Lycoming granted NO core credit)

#4: Continental O-300-D, (1700hrs since new) #5 Exhaust valve burned, gradually degraded differential pressure checks over a period of 5 years. Lapped valve on two separate occasions during those five years. Eventually removed from service during the 5th annual due to Zero compression on differential pressure test. Replaced with overhauled cylinder--engine inspected and returned to service. (Flew for 4 hours a couple days before the issue, with no defects noted)

Here is a pic of that overhauled cyl:
11057256_878060275570223_3910769108280091518_n.jpg


#5: Continental O-300-D, (1770hrs since new) #4 Exhaust valve stuck, low EGT during preflight runup (flight aborted). Discovered cracked rocker boss upon inspection. Removed cylinder from service, also removed #2 cylinder from service for unrelated minor issues. Inspected engine internals (cam lobes, etc). Replaced #2 and #4 cylinders with factory new Millennium cyls, using all new hardware and new wrist pins, removed & cleaned all remaining cyl exhaust valves, honed guides, installed new springs & keepers. Engine returned to service.
12002768_971674392875477_1618327860781145728_n.jpg


That was a couple years ago, and it still runs great! Incidentally, I flew the plane 12.2 hrs the day prior to the issue (Boston to Springfield, SD), and it flew beautifully!

YMMV!
-Dana
 
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Sort of like the medics do with older people! We like to know how we are going to 'go'![/QUOTE]
Let'sgoflying! said:
So more and more people are running engines past TBO it seems; I wanted to poll the experiences of the group to find out what the most likely symptom was, of a failing engine.
Especially with regards to bottom end failure - not cylinders, as they are to me not really a sign of engine end-of-life.

We've all heard of lot of predictions and suppositions about what a person might expect, "making metal", "high oil consumption", "not making power", "internal component failure", etc etc (add yours supposition here if you must)

But if we were to accumulate data it would be actual experiences, not predictions.

Have you had an engine (or been closely involved with an engine) which ran past TBO and then failed, or was removed from service because of end-of-life symptoms? What was/were the symptom.

Let'sgoflying! said:
So more and more people are running engines past TBO it seems; I wanted to poll the experiences of the group to find out what the most likely symptom was, of a failing engine.
Especially with regards to bottom end failure - not cylinders, as they are to me not really a sign of engine end-of-life.

We've all heard of lot of predictions and suppositions about what a person might expect, "making metal", "high oil consumption", "not making power", "internal component failure", etc etc (add yours supposition here if you must)

But if we were to accumulate data it would be actual experiences, not predictions.

Have you had an engine (or been closely involved with an engine) which ran past TBO and then failed, or was removed from service because of end-of-life symptoms? What was/were the symptom(s)?

Not saying we don't want to hear your hypotheticals and other thoughts on the topic, but I was truly looking for first- or maybe second-hand experiences with the above paragraph.

I'd like to list these actual, real-life observed symptoms for failing old engines in a list:
ie (this is merely an example of what I think a final list would look like)

I do not have real numbers here but in my 44 years in the engine business the last 24 years of which I was manager or owner of major engine shops I have seen a LOT in the give or take 9,000 engines IRAN'd or overhauled. I am assuming you are targeting engines that failed to run as well as those that were overhauled or IRAN'd.

1-45% most likely is spun or seized a main bearing, eng would not start or run properly.
Call this 1% as I have seen this maybe 100 times for the reasons you state!

2-20% second most likely is could not maintain oil pressure.
Less than 500 for 5%

3-10% third by likelihood was case crack noted.
This one would run in excess of 10% for maybe 1,000

4th-5% metal in filter.
This could exceed 15%!

5th 5% loss of prop control due to metal in gov screen.
Negligible. Maybe 5 or less for this specific reason. Loss of prop control due to failure of the oil transfer system ( collar or main bearing) might be 75

6th 5%cam lobe failure, cylinder would not fire.

Have only seen a cam so bad cylinder(s) would not fire only a couple of times. Cam or tappet failures found as a result of metal or loss of performance would likely be close to a thousand or so with another 1000 or so failed cams that were found upon teardown for things not related to cam function.

7th 2% no symptoms but multiple accessory/cylinder failures forced the issue.
A significant number of engines ended up as unplanned overhaul due to economic practicality. If you replace a bunch of accessories and all the cylinders you can spend half the cost of an overhaul. There are a lot of factors involved in this type of decision such as resale and length of intended ownership. Cost is of course a major factor.

I have seen many relatively low time engines that needed overhaul and others way over TBO that really did not need overhaul. A few years ago Zephyr overhauled a 4400 hour Lycoming IO-360-L2A that had over 4000 hours on the lower end. Cylinders were replaced at 2000. The cam was just starting to go and would have run hundreds more hours. At G & N we got an O-320-H2AD back as a core that had 3976 hours on it and never had a cylinder off. Prinair in San Juan ran their Continental IO-520-E engines to 4500 with tops at 1500 and 3000.


Charlie Melot Sales/Production manager Mattituck, General manager G & N, Managing partner Penn Yan Aero and finishing with 25 years ownership of Zephyr
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