Engine condition analysis

[Beech Bum]

I have justdone my first oilchange and plug change on my O-360 A4J. While the plugs were being cleaned I thought it prudent to do a blow-by measure. The cylinders tested 1-4 as follows 75;76;69;68. The engine has 528 h SMOH. Should all cylinders not be more or less the same? Interestingly the two rear cylinders 3 & 4 has a much lowerreading than the front two. Maybe a factorof running hotter at the back?maybe someone who knows more can advise me on this?

[SparkBerry]

Saw this post hasn't been replied to and thought someone needs to step up

Your cylinder readings do not seem abnormal at first glance and are probably perfectly fine, however there are many factors contributing to cylinder condition that need to be factored in. Yes the rear cylinders do run slightly hotter, but on a four cylinder Lycoming, when flown by the book, the difference is not massive at all.

The first point I'd like to highlight is that the differential pressure check should never be taken as a stand alone measurement of engine condition, as they can be misleading to those with little experience in maintaining aircraft piston engines. I have had my share of customers telling me " but my blowbyes are in the 70's" only for me to point out that their cylinders glazed so badly, that one could see their teeth in the reflection in that polished mirror finish. Oil soaked cylinders can seal rings as well as ones with low time and perfect hone marks (cross-hatching as we call it). No cross hatching gives the oil room to go where it pleases, and that's a bad thing. A sudden increase in oil consumption is a dead giveaway. Lycoming SI1427C prescribes oil consumption guidelines to that end.

Secondly, when it comes to checking the cylinder compression, always obey the manufacturer's recommendations (in this case Lycoming SI1191A) on how this procedure should be carried out. It goes without saying that the correct tools and calibrated gauges should always be used. A quick way to see if the gauges correspond correctly to each other is to dial them up against one other before plugging into the cylinder. If the gauges do not read the same then you have already started on the back foot ( Always remember to not have pressure in the line when plugging in or out of the cylinder).

Then comes the questions I have for you. Was the compression check done on a hot engine? This is an important aspect as you want the rings to be seated as closely as they can be to flight conditions. What did the plugs look like? Were they burned white, brown, sooty or oiled? Did you remove and cut the oil filter and check for metal?

Where did the compression go? When you remove the dipstick did you hear whistling out the filler neck? Or did you hear whistling out the exhaust? It is important to note that rings never seal perfectly, however if the sound coming out the filler neck is notably different between the cylinders then that should warrant further investigation or troubleshooting. Sometimes a hard flight will sort it out or an experienced hand on the prop can help seat the rings better, something I advise against if you are not familiar with the tricks, much like prop swinging, this can result in serious injury. Was there any noise out the exhaust? If so, I would advise that you try and remedy that immediately. Sometimes a piece of foreign matter, usually carbon, can cause the exhaust valve to not seat correctly, resulting in a distinct exhaust blow. A good smack to the exhaust rocker with a rubber mallet by an experienced hand can often remedy this, but often one needs to look into the cylinder with a borescope to see the source of the leak. A visual inspection can often reveal a hotspot on the valve which could in result in short term performance degradation and eventually substantial damage to the engine.

On the subject of a borescope, I'm a huge fan of doing borescope inspections along with compression test, because as I have previously stated, compression test don't always show the condition inside the cylinders. An aircraft that flies 500 hours a year will more often than not have cylinders that are in superior condition to engine that has done 100 hours in five years. Most Lycoming cylinders have either nitrided or plain steel barrels and these cylinders want to be flown. Letting them stand idle for extended periods, not flying them hard when new to break-in the rings, or improper inflight engine management can often result in poor cylinder condition. An engine that stands is an engine that doesn't last. These cylinders corroded easily if not looked after (let's not even mention Lycoming camshafts ). Pitting from corrosion on the cylinder barrels can often result in not just new rings, but new cylinders outright if they cannot be ground oversize. Fly the plane preferably for more than an hour at at a time regularly and do oil changes as prescribed by the manufacturer and the cylinders will likely last the full TBO. If you are a regular flyer, then oil analysis (which can be done locally) is also something I'd recommend and is not costly.

Bottom line is if you look after then engine and fly her regularly, do your oil changes manage the engine properly in flight, then your engine will last. They are designed to be reliable, but that is only true if the owner plays their part. If performance is matching the charts, if shes using oil within the limitations and the oil is not turning black soon after every oil change, and mag drops are few and far between, then your engine should be fine if you look after her.

I would recommend you download the O-360 Operator's Manual, which is freely available on the Lycoming website and use this as your go-to publication as the owner of that engine.

Hope this helps a little

[Rotor kop]

Nice post SB interesting to read. Your comment in hot/cold engine is so true. A blowby was done on my engine and looked lower than usual. Later in the day it was done again and was higher than usual

[Beech Bum]

Excellent advise, thank you. I have downloaded the 0360 manual and am studying it Intensely. I have send away oil sample to wearcheck and they have found very high fine metal content. After 10 hours changed oil and still unusually high. I have not cleaned strainer at oilchange and wonder if residual metal might have contaminated oil sample?
I also went through logbooks in detail and found that the engine was inoperative for biggest part of 4 years. The AMO has ground run the engine regularly and ensures me that this was done sufficiently. I doubt that as the owner has had the CofA also lapsed during this time. A yearly MPI was done and Oil changes but I think the metal content is due to fine rust. I will have the engine completely inspected at this MPI(Feb)

[Pete]

Great post Sparkberry

[Segg]

Excellent advise, thank you. I have downloaded the 0360 manual and am studying it Intensely. I have send away oil sample to wearcheck and they have found very high fine metal content. After 10 hours changed oil and still unusually high. I have not cleaned strainer at oilchange and wonder if residual metal might have contaminated oil sample?
I also went through logbooks in detail and found that the engine was inoperative for biggest part of 4 years. The AMO has ground run the engine regularly and ensures me that this was done sufficiently. I doubt that as the owner has had the CofA also lapsed during this time. A yearly MPI was done and Oil changes but I think the metal content is due to fine rust. I will have the engine completely inspected at this MPI(Feb)

If you can, get your AMO to check the cam shaft's lobes - don't know if there's another way apart from popping off a cylinder though...

Has wearcheck told you your levels are "very high" compared to similar engines or is it just their opinion?

From what I understand, ground running an engine is NOT a good thing to do, as it doesn't get up to a high enough temperature for a long enough period of time to get rid of any moisture

[Beech Bum]

Let me give some more information regarding Wearcheck reports: Report one was on oilchange of 50 hours. I did not know that with a strainer I need to change every 25 hours. The iron content was 365 parts per million with other metals and silicon negligable. After fifteen hours the Fe content was 118 ppm. It still is very high and the reports refer to the metal particles as due to rubbing - very fine particles.your thoughts on this?

[SparkBerry]

Excellent advise, thank you. I have downloaded the 0360 manual and am studying it Intensely. I have send away oil sample to wearcheck and they have found very high fine metal content. After 10 hours changed oil and still unusually high. I have not cleaned strainer at oilchange and wonder if residual metal might have contaminated oil sample?
I also went through logbooks in detail and found that the engine was inoperative for biggest part of 4 years. The AMO has ground run the engine regularly and ensures me that this was done sufficiently. I doubt that as the owner has had the CofA also lapsed during this time. A yearly MPI was done and Oil changes but I think the metal content is due to fine rust. I will have the engine completely inspected at this MPI(Feb)

If you can, get your AMO to check the cam shaft's lobes - don't know if there's another way apart from popping off a cylinder though...

Has wearcheck told you your levels are "very high" compared to similar engines or is it just their opinion?

From what I understand, ground running an engine is NOT a good thing to do, as it doesn't get up to a high enough temperature for a long enough period of time to get rid of any moisture

Hi Segg

After weeks of research into Lycoming camshaft wear I can advise this:

There are two main reasons why Lycoming camshafts wear badly. First one is low idle. They require splash oil for lubrication and idling on the ground at 700 rpm isnt ideal. The second one, and it's particularly bad on flat tappet engines, is this: the nitrided cams sit on top of the engine and nitrided surfaces are hard but corroded easily. The top of the Lycoming crankcase is were all the condensation forms. The math is simple. The rusted surface turns the camshaft and followers into a scotchbrite on scotchbrite situation, rapidly wearing down the lobes. This I believe is the primary reason why the new engines all come with roller followers now and not flat followers. Oil also plays a crucial role. Lycoming flat tappet engines must use the anti-scuff additive oils such as W100 Plus after engine run in.

The easiest way to check cam wear is to remove the rocker box covers and measure the depression of the valve spring when there is no clearance. All the valve springs must depress the same. I usually use the rocker face as the flat surface for reference and measure with a vernier. If any of the valve springs do not depress the same when turning over the engine, then it's almost certain that that camlobe is worn, and if that lobe drives a valve on the opposite side of the engine and that valve measures the same, then the lobe is worn.

I developed this method after alot if research and it has never failed me. Every single time I make the measurement and the valve depression are different, we pull the cylinder and find a worn lobe. This is the simplist non-invasive procedure to determine cam wear.

[Segg]

Excellent advise, thank you. I have downloaded the 0360 manual and am studying it Intensely. I have send away oil sample to wearcheck and they have found very high fine metal content. After 10 hours changed oil and still unusually high. I have not cleaned strainer at oilchange and wonder if residual metal might have contaminated oil sample?
I also went through logbooks in detail and found that the engine was inoperative for biggest part of 4 years. The AMO has ground run the engine regularly and ensures me that this was done sufficiently. I doubt that as the owner has had the CofA also lapsed during this time. A yearly MPI was done and Oil changes but I think the metal content is due to fine rust. I will have the engine completely inspected at this MPI(Feb)

If you can, get your AMO to check the cam shaft's lobes - don't know if there's another way apart from popping off a cylinder though...

Has wearcheck told you your levels are "very high" compared to similar engines or is it just their opinion?

From what I understand, ground running an engine is NOT a good thing to do, as it doesn't get up to a high enough temperature for a long enough period of time to get rid of any moisture

Hi Segg

After weeks of research into Lycoming camshaft wear I can advise this:

There are two main reasons why Lycoming camshafts wear badly. First one is low idle. They require splash oil for lubrication and idling on the ground at 700 rpm isnt ideal. The second one, and it's particularly bad on flat tappet engines, is this: the nitrided cams sit on top of the engine and nitrided surfaces are hard but corroded easily. The top of the Lycoming crankcase is were all the condensation forms. The math is simple. The rusted surface turns the camshaft and followers into a scotchbrite on scotchbrite situation, rapidly wearing down the lobes. This I believe is the primary reason why the new engines all come with roller followers now and not flat followers. Oil also plays a crucial role. Lycoming flat tappet engines must use the anti-scuff additive oils such as W100 Plus after engine run in.

The easiest way to check cam wear is to remove the rocker box covers and measure the depression of the valve spring when there is no clearance. All the valve springs must depress the same. I usually use the rocker face as the flat surface for reference and measure with a vernier. If any of the valve springs do not depress the same when turning over the engine, then it's almost certain that that camlobe is worn, and if that lobe drives a valve on the opposite side of the engine and that valve measures the same, then the lobe is worn.

I developed this method after alot if research and it has never failed me. Every single time I make the measurement and the valve depression are different, we pull the cylinder and find a worn lobe. This is the simplist non-invasive procedure to determine cam wear.

That sound much better than pulling cylinders - to what degree can you measure the wear? Can you identify the early stages?

[SparkBerry]

Excellent advise, thank you. I have downloaded the 0360 manual and am studying it Intensely. I have send away oil sample to wearcheck and they have found very high fine metal content. After 10 hours changed oil and still unusually high. I have not cleaned strainer at oilchange and wonder if residual metal might have contaminated oil sample?
I also went through logbooks in detail and found that the engine was inoperative for biggest part of 4 years. The AMO has ground run the engine regularly and ensures me that this was done sufficiently. I doubt that as the owner has had the CofA also lapsed during this time. A yearly MPI was done and Oil changes but I think the metal content is due to fine rust. I will have the engine completely inspected at this MPI(Feb)

The suction filter on the sump is what we AME's often refer to as the "rock/cow catcher" because that's all they're really good at filtering. If your engine has a proper full flow pressure element, then that is the best place to look for proper metal filings. That ideally should be cut and inspected every oil change. Squeezing the excess oil out of the filament in a vice help will push out oil that could mask the metal. Then unravel that element and let it tell the story. That's where you'll usually find filings and they can be identified with a magnet. I have had it in the past where that is not always the case because the metal is so fine not even the magnet will pick it up. A some small filings is no need for panic, especially on a new engine, but if it's a regular occurrence then start asking questions. Also high time engine, or engine that are chewing oil ( in other words, chewing rings), will normally have an excessive build up of carbon in both filters.

The wear normally gets really bad really quickly when an aircraft has been standing and is then thrust into regular usage in say, a flight school. Don't forget what I said about the borescope in the cylinders. Don't go straight for the bottom of the sleeve, rather look at the ceiling, because that's where the condensation occurs. If you see it's pitted badly, expect regular mag drops ahead, and then a top overhaul in time to come.Oil consumption increases tell the story of whats going on in the cylinders. That's for the cylinders, however if you do find metal in the filter, it's most likely from the cam given this aircraft's history, but again I'm no witch doctor and not all aircraft behave badly in the same way. The rust you speak of is likely cylinders barrel material, as this is often fine enough to evade detection in the oil filter cutting.

As for the regular ground running, that's never good enough. As weird as it may seem, oil can actually hold water in an emulsified state or in the form of acids mixed in the oil. This isn't odd, as the combustion process in the cylinders produce water and carbon as a byproduct. Carbon and acid in the oil will attracts more water, and a snowball effect on a microscopic level occurs. This is this, along with the degradation of the lubricating properties of oil and the build up of contaminants is why we do oil changes. You can however get rid of that water by allowing the the oil to heat up by running the engine to the point where the water will boil away, and that implies you need to get the oil above 180 degrees Fahrenheit, with 210 degrees being the boiling point of water at sea level. When is the last time you saw these temperatures on a normal quick ground run? You need to fly her to give the oil the opportunity to get rid of the water and acids.

[Beech Bum]

Hi SparkBerry
Thank you for the wealth of information and for taking the time to assist. The MPI is due in two weeks. I am certainly going to investigate all your suggestions thoroughly and post results here.
Best Regards
BB

[SparkBerry]

If you can, get your AMO to check the cam shaft's lobes - don't know if there's another way apart from popping off a cylinder though...

Has wearcheck told you your levels are "very high" compared to similar engines or is it just their opinion?

From what I understand, ground running an engine is NOT a good thing to do, as it doesn't get up to a high enough temperature for a long enough period of time to get rid of any moisture

Hi Segg

After weeks of research into Lycoming camshaft wear I can advise this:

There are two main reasons why Lycoming camshafts wear badly. First one is low idle. They require splash oil for lubrication and idling on the ground at 700 rpm isnt ideal. The second one, and it's particularly bad on flat tappet engines, is this: the nitrided cams sit on top of the engine and nitrided surfaces are hard but corroded easily. The top of the Lycoming crankcase is were all the condensation forms. The math is simple. The rusted surface turns the camshaft and followers into a scotchbrite on scotchbrite situation, rapidly wearing down the lobes. This I believe is the primary reason why the new engines all come with roller followers now and not flat followers. Oil also plays a crucial role. Lycoming flat tappet engines must use the anti-scuff additive oils such as W100 Plus after engine run in.

The easiest way to check cam wear is to remove the rocker box covers and measure the depression of the valve spring when there is no clearance. All the valve springs must depress the same. I usually use the rocker face as the flat surface for reference and measure with a vernier. If any of the valve springs do not depress the same when turning over the engine, then it's almost certain that that camlobe is worn, and if that lobe drives a valve on the opposite side of the engine and that valve measures the same, then the lobe is worn.

I developed this method after alot if research and it has never failed me. Every single time I make the measurement and the valve depression are different, we pull the cylinder and find a worn lobe. This is the simplist non-invasive procedure to determine cam wear.

That sound much better than pulling cylinders - to what degree can you measure the wear? Can you identify the early stages?

See my reply to Beech Bum about checking for metal in the oil filter. The Wear Check SOAP sampling also helps a great deal but must be used as trend monitoring procedure and not just a once of check as so often happens.

When the cam lobes wear they decrease valve lift. The effect is a decrease in volumetric efficiency of the of the engine, which means a decrease in overall engine power. As cam wear is something that doesn't just happen overnight, you may not notice the decrease in performance immediately, until you take off from a Highveld airfield on a hot day and suddenly those trees on the end of the runway seem to be climbing up to meet you An issue like this is what lead me down the road of studying what can cause poor performance when the answer isn't obvious.

I must stress that there are many things that can cause an engine to under perform, however the rest of the troubles are often much easier to find, such as carbs or mags et al. Before devising procedure, I calculated an 8% difference in power between two identical engine with identical components and propellers, and after lengthy troubleshooting, I speculated there must have been a volumetric deficiency at play, and engine valves were the prime suspect. I took measurements and found a millimeter difference in valve spring depression on two valves running from the same lobe, from the other six in the engine. A millimeter is all it took. We pulled a pot and my theory was proven correct. I have since pulled several engines using the same technique and it has never been wrong. Pulling a pot validates the test every time.

[KEO]

Thanks for this post and the answers. I have learned a lot.

[Jayson v Schalkwyk]

Hello all,

My IO-540W1A5D is being overhauled at the moment (timex). I bought the aircraft with only 170 odd hours to go so it was inevitable. Now that the engine will be new, I want to give it the best chance I can.

I realise that Wearcheck is a trend analysis not a once off. Can some one give me more insight in to the actual procedures. Do I need an agreement in place with Wearcheck? Oil change every 50hrs? Do they send you the necessary "sampling kit" and you then just send it back to them?

Many thanks.

[KEO]

Jason I bought a box of ten samples. They send you the sample bottles which you return to them with all the data. Run your engine, take a sample and ship it off with the paperwork. It is an invaluable tool. See the links below for more info.

https://www.lycoming.com/content/why-oi ... -important

https://www.lycoming.com/sites/default/ ... 261971.pdf