Borescope shows corrosion

[Justin Schmidt]

53 minutes ago, PT20J said:

Lycoming brought cylinder head machining in house just before Covid and was working through start up issues when the factory shut down for Covid. Then, during Covid owners decided it was a good time to overhaul and homebuilders decided it was a good time to order engines (Lycoming told me that Van’s is by far their largest customer now). Orders spiked and production was halted. They are still trying to catch up although they have 6 automated head machining lines running 24/7. Lead time was a year when I visited the factory last fall. Not sure what it is now. 

Skip

 

Going through an OH now, new Lycoming Cylinders were around 2 years (April 2023).

[rotorman]

4 hours ago, Pinecone said:

It seems like the best move would be to order cylinders, but keep flying.  With some luck, you won't need the cylinders until after they are delivered.

AFAIK you cannot rebuild chromed cylinders.

How about some speculation about why rust accumulates on cylinders that are only 3 years old and have been broken in properly and run nearly weekly for a total of 120 hours. and don't live in a particularly wet part of the US.  Or is it just that few engines that fit this profile have been borescoped and so they remain unknown.

[PT20J]

Hard to tell without earlier borescope pictures. 

[A64Pilot]

31 minutes ago, rotorman said:

How about some speculation about why rust accumulates on cylinders that are only 3 years old and have been broken in properly and run nearly weekly for a total of 120 hours. and don't live in a particularly wet part of the US.  Or is it just that few engines that fit this profile have been borescoped and so they remain unknown.

My swag is there was the beginnings of corrosion on the cylinders when they were plated, otherwise we have to assume the person who put them on was blind, or the boss said use them anyway. The rust has to occur under the chrome doesn’t it? Does chrome rust? 

Chrome is very rust resistant, any environment that could rust chrome would eat plain cylinders, so that’s why I’m putting the fault on the chromer whoever that was. That was their primary selling point, chrome can sit without rusting, plain steel bores can’t.

I’m speculating that they could have looked OK on a visual inspection.

Edited July 13, 2023 by A64Pilot

[A64Pilot]

Not that I like that Cylinders are back ordered two years, but hearing that Lycoming has such a good book of business I think bodes well for their continued survival.

[Ragsf15e]

52 minutes ago, A64Pilot said:

My swag is there was the beginnings of corrosion on the cylinders when they were plated, otherwise we have to assume the person who put them on was blind, or the boss said use them anyway. The rust has to occur under the chrome doesn’t it? Does chrome rust? 

Chrome is very rust resistant, any environment that could rust chrome would eat plain cylinders, so that’s why I’m putting the fault on the chromer whoever that was. That was their primary selling point, chrome can sit without rusting, plain steel bores can’t.

I’m speculating that they could have looked OK on a visual inspection.

I don’t think he said he has chrome cylinders.  He said chrome plated rings which is consistent with steel cylinders, no?

[PT20J]

The chrome comes from the rings being abraded by the rough cylinder walls. Those cylinders are steel as evidenced by the cross hatch honing pattern. 

[Pinecone]

OP stated the chrome and nickel are high in oil analysis, but staying steady.

Leaning more to run them and monitor.   Since they are not chromed bore, they can be overhauled.

 

[PT20J]

The purpose of the oil analysis is to alert you to something out of the ordinary so you can further investigate. In this case, borescope inspection found the problem causing the high chrome. The engine is running fine and this is not something that should cause sudden catastrophic failure, so if it were mine, I would keep running it while planning for an eventual top overhaul. With two year lead times, I would probably order new cylinders now.

The nickel might indicate an exhaust valve guide issue. This could be checked with a wobble test. The biggest risk here would likely be a stuck valve and I'd be on the lookout for any morning sickness symptoms. If a valve gets tight due to deposits, you can always do the rope trick and ream it.

Skip

[rotorman]

They are not chrome cylinders. 

Thanks everyone for your inputs. I'm awaiting Western Sky's opinion after they review the photo's and will report back.

[EricJ]

5 hours ago, Pinecone said:

OP stated the chrome and nickel are high in oil analysis, but staying steady.

Leaning more to run them and monitor.   Since they are not chromed bore, they can be overhauled.

 

Depending on how much pitting there is, they may not be candidates for honing.   It'd be hard to say whether they're reusable until they're off.

[Utah20Gflyer]

4 hours ago, rotorman said:

They are not chrome cylinders. 

Thanks everyone for your inputs. I'm awaiting Western Sky's opinion after they review the photo's and will report back.

When you say the engine has been run weekly does that mean it has flown every week or would that include ground runs?   A lot of ground running can be the cause of severe corrosion as it creates a build up of water in the engine.

[A64Pilot]

8 hours ago, EricJ said:

Depending on how much pitting there is, they may not be candidates for honing.   It'd be hard to say whether they're reusable until they're off.

I thought chrome.

But yes I believe .010 is all you can oversize, and if these weren’t new it may be that’s where they are now.

If they are steel, I’d just run it, it will get slightly better over time if you don’t let it sit.

As hard as cylinders are to get I’m not sure he has much option anyway.

[Old Chub]

Is everyone sure this is corrosion ?   

Not sure from the photos but almost appears to by some type of staining.   Like when you acid etch a metallurgical sample for examination. 

 

 

[1980Mooney]

19 hours ago, PT20J said:

The purpose of the oil analysis is to alert you to something out of the ordinary so you can further investigate. In this case, borescope inspection found the problem causing the high chrome. The engine is running fine and this is not something that should cause sudden catastrophic failure, so if it were mine, I would keep running it while planning for an eventual top overhaul. With two year lead times, I would probably order new cylinders now.

The nickel might indicate an exhaust valve guide issue. This could be checked with a wobble test. The biggest risk here would likely be a stuck valve and I'd be on the lookout for any morning sickness symptoms. If a valve gets tight due to deposits, you can always do the rope trick and ream it.

Agree - and over the next two years monitor it. - at the rate the OP has been flying it, it will only have about 200 hours.  If it stabilizes without increased oil consumption or loss in compression, I would just keep flying - just my 2 cents.

The thought of a "precautionary" top overhaul at only 200 hours makes me ill.  But @rotorman if, out of an abundance of information (too much?) and caution, that is what you want to do, then do it.

[A64Pilot]

Thing is, excessive blow-by is damaging, it quickly contaminates oil with abrasive carbon and acids and some believe a Lycomings cam as it’s directly in line with the cylinders is blasted if you will with blow by and that may be one cause of cam / lifter failure.

If I were to continue to fly an engine with excessive blow by, I’d shorten my oil change interval

It will almost certainly stabilize and is likely to even get better

Edited July 14, 2023 by A64Pilot

[PT20J]

Didn’t the OP say he was getting 9 hrs/qt? Doesn’t sound bad. 

[larrynimmo]

On my 650 hour Lycomming IO360 that I aggressively broke in I always had considerable oil consumption…typically 1 quart 5-8 hours but oil stays clean and I change it every 25 hours.  Since I only add 6 quarts at oil change, I keep my oil at 6 and add when it goes below…by the time I do my 25 hour oil change , I drain back out 5.5quarts and had used 3 quarts.

summary 9 quarts lasts me 25 hours.

I wish I had lower consumption, but it is what it is and it is stable…never metal in filter or screen…cylinders look good with nice cross hone except there is some scaping wear above spot on cylinders where the rings are at top dead center

my engine also leaks at the main shaft seal for the propellor…but doesn’t leak much…mechanic said it’s not worth the effort to change it

[A64Pilot]

We get spoiled by our automobiles with their water cooled engines, small cylinders and extremely tight tolerances that water cooling allows and their near zero oil consumption and we of course think that’s how it should be.

Aircraft engines have huge cylinders, 90 cu in per cylinder and as they are air cooled temps vary widely and add in that no matter how they are run they must never be allowed to seize and you end up with sloppy clearances, so when they are in perfect condition they burn oil, they are supposed to, heck even the oil is formulated so that when it burns it doesn’t leave much deposits. Low or no oil consumption is not desirable.

So what it boils down to is as long as we aren’t fouling plugs excessively, the thing starts well, isn’t blowing smoke when running and it makes good power as long as consumption isn’t more than 6 quarts every 10 hours, there is nothing that needs fixing, it’s airworthy. Compression of course must meet spec too.

Before I overhauled my IO-540 it burned a quart every 4 or 5 hours, it was close to TBO. I bought new cylinders, set the ring gap at min tolerance, built the engine as perfect as I could, broke it in correctly and was looking forward to 1 qt every 10 or more hours.

Nope, it burned 1 gt every 4 or 5 hours, same consumption it had before overhaul. Some engines for reasons that I don’t know why just consume more oil than others, it really to some extent isn’t a metric on how healthy an engine is.

I’m not saying pitted cylinders are fine, they aren’t. he has excessive wear as evidenced by oil analysis, his rings won’t live as long as they would without the pits, but that’s not to say that there isn’t say at least 1,000 hours in them. I think over time the edges of the pits that are causing wear will wear it and wear rate will come down some.

Except for higher than average metals he would never have known

[rotorman]

2 hours ago, A64Pilot said:

We get spoiled by our automobiles with their water cooled engines, small cylinders and extremely tight tolerances that water cooling allows and their near zero oil consumption and we of course think that’s how it should be.

Aircraft engines have huge cylinders, 90 cu in per cylinder and as they are air cooled temps vary widely and add in that no matter how they are run they must never be allowed to seize and you end up with sloppy clearances, so when they are in perfect condition they burn oil, they are supposed to, heck even the oil is formulated so that when it burns it doesn’t leave much deposits. Low or no oil consumption is not desirable.

So what it boils down to is as long as we aren’t fouling plugs excessively, the thing starts well, isn’t blowing smoke when running and it makes good power as long as consumption isn’t more than 6 quarts every 10 hours, there is nothing that needs fixing, it’s airworthy. Compression of course must meet spec too.

Before I overhauled my IO-540 it burned a quart every 4 or 5 hours, it was close to TBO. I bought new cylinders, set the ring gap at min tolerance, built the engine as perfect as I could, broke it in correctly and was looking forward to 1 qt every 10 or more hours.

Nope, it burned 1 gt every 4 or 5 hours, same consumption it had before overhaul. Some engines for reasons that I don’t know why just consume more oil than others, it really to some extent isn’t a metric on how healthy an engine is.

I’m not saying pitted cylinders are fine, they aren’t. he has excessive wear as evidenced by oil analysis, his rings won’t live as long as they would without the pits, but that’s not to say that there isn’t say at least 1,000 hours in them. I think over time the edges of the pits that are causing wear will wear it and wear rate will come down some.

Except for higher than average metals he would never have known

The last statement here is not exactly correct. The local shop did the borescope and generated a log book entry that all cylinders show corrosion. Even if a dishonest person didn't put the entry in his logbook, a pre-buy inspection, if performed by the same shop would probably bring it to light. So if I were planning to sell this airplane, who would be willing to buy it with corroded cylinders? How much would it knock of the value of the airplane if a buyer could be found willing to buy it in this condition?

[A64Pilot]

What’s incorrect about it?

He had it borescoped only because of the high metals, and as far as the logbook entry if he’s a Savvy follower he doesn’t allow any logbook entries, only stickies he keeps in a shoe box, that allows him to dispose of any entries that don’t enhance sales value after one year.

Sure a borescope would find it as does a compression test usually, and only a fool would buy an airplane without scoping it, but what does that have to do with this case where the engine is operating fine, without excess oil consumption and the only indicator was high chrome? Most don’t scope unless there is a problem, just like this time.

Without the high chrome he wouldn’t have scoped and if he didn’t scope he wouldn’t have known, until or unless there were symptoms.

I bet that corrosion pitted cylinders aren’t uncommon at all.

I’m not saying they don’t decrease the value of the aircraft, I think they do, but if it were me, I’m not so sure that I would replace them now for that reason.

Its sort of like a gear up, yes it decreases the value of the aircraft, but in truth the aircraft is often in better condition after one.

Which is sort of a moot point, because Lycoming cylinders aren’t available for two years, and I don’t know if I would put ECI ones on myself with the current ones working fine, just because Lycoming cylinders are I believe the gold standard, ECI maybe not.

But I think I would get a set of Lycoming cylinders on order because if nothing else I don’t think they would be hard to sell when you get them two years from now.

I wonder if these cylinders could be nickel plated? They seem to work much better than chrome? By nickel I mean nickel / ceramic by whatever name it’s given

[A64Pilot]

This link says Cermanil works in everything except Mooney’s.

What’s different with Mooney’s?

https://www.aviationconsumer.com/maintenance/cerminil-or-not/