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Cylinder replacement...... DANGER! DANGER!

M

MoJo

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I just read a popular aviation magazine article about replacing a cylinder/cylinders without a major or being on a stand, and it says that it is almost never done correctly, and it is mostly luck that a replaced cylinder doesn’t fail.

Big question... Do you torque cylinder studs wet or dry?

One thing the article didn’t cover is the percentage of failed replaced cylinders vs not replaced.
 
The torque is done wet or dry as spelled out in the maintenance manual.

I think the author needs to come up here for a season or two and try to explain these claims. Apparently we are extremely lucky. Replacing a cylinder is just a maintenance item.

Web
 
MoJo said:
I just read a popular aviation magazine article about replacing a cylinder/cylinders without a major or being on a stand, and it says that it is almost never done correctly, and it is mostly luck that a replaced cylinder doesn’t fail.

Big question... Do you torque cylinder studs wet or dry?

One thing the article didn’t cover is the percentage of failed replaced cylinders vs not replaced.
Click to expand...
Can you post a link this BS.
 
It is Mike Busch. He’s been preaching this for years. He may have a point when it comes to the big Continental motors. It my short time in the Bonanza world there seem to be enough engine failures within 200 hours of cylinder replacement to get one thinking. I witnessed my ex partner top the engine in what’s now his Bonanza. He did it by the book and explained what mistakes are easy to make if someone is not educated or willing to learn.

As far as small Continentals and all Lycomings , my opinion is Mr. Busch is over concerned.
 
Sadly big Continentals have been plagued with bad cylinders for a long time so changing them and having subsequent failures may be attributed to bad cylinders. Once you get them fixed right they seem to work fine.
 
The failures Mike Busch worries about are rods coming through the case due to improper torque and reuse of through stud nuts or even wrong nuts or one I personally saw, the special nuts installed upside down. That failure killed two people in a 210. Improper procedures can end up with a bearing spinning during or shortly after installation.

I think when a competent mechanic does a top using proper new or serviceable parts and following the proper procedure, that would be a safe engine to fly.
 
This article is a load of crap. He says not to blame the mechanic for cylinder failure then lists all the stuff the mechanic does/doesn't do that causes the failure. The long and short of this is that cylinder replacement is an unfortunate maintenance item. When the cylinder is determined to have 'failed', there are manufacturer's instructions on how to remove and then replace it. There are also manufacturer's instructions on how to determine if a replacement cylinder is serviceable (whether new or overhauled).

If a cylinder fails due to engineering or metalurgical issues, this is not the fault of the mechanic or operator. If the cylinder fails due to not following the instructions in the manual, THAT is the fault of the mechanic. Items such as improper torque procedures or not replacing any mandatory replacement items is squarely the fault of the mechanic.

Any one of us authorized to do maintenance (even you pilots are authorized certain maintenance items) take on the responsibility of performing all such operations correctly. We are even bound by regulation to use the correct manuals/information that is available. While we may raise issue with what may seem to be improper maintenance instructions, we must rely on the proper manuals to perform all maintenance.

To sum it up, 'do the job'. If you replace a cylinder, do it per the appropriate instructions. EACH and EVERY instruction. If you do that, the cylinder will be just fine.

Web
 
Yeah, Mike Busch, the self proclaimed "expert on aircraft maintenance" who has very little actual maintenance experience.....?

He reads a lot, then writes and presents.....

I've posted this before, but on the large Continentals we ran in Cessnas, specifically on floats, which is not kind to engines, when our maintenance folks started using only new cylinders, most of our cylinder "failures" went away. Buy junk cylinders that've gone through ten or fifteen runs and you may be buying someone else's mistakes.

But, failures due to mechanics not installing "right".....seriously?

MTV
 
Rich, Nobody touches rod nuts during a top. I don't get that one. But I don't get most of what that article says.
 
Stewart,
I wasn’t referring to rod nuts. Sorry I see that I wasn’t being clear. Some failures I’m familiar with, two actually, were determined to be rod failures due to bearings spinning and then those bearings not being lubricated properly. The primary cause was determined to be improper cylinder replacement allowing the case halves to shift subsequent to the work. Generally goes back to improper torque and/or procedure.
I am not an A&P but spent a lot of time with my ex partner who is and also an IA and DAR discussing these issues before he topped our IO-520.
I totally agree with Web. A competent mechanic using proper tools, parts and manuals would not scare me. The guy who changes one cylinder on his IO-520 and fails to torque the through stud nuts from both sides with two torque wrenches is asking for a catastrophic engine failure down the line. For example.

Rich
 
Well, I've read enough of Mike's stuff, and talked to him enough, to only take his articles with the appropriate grain of salt. He makes some good points sometimes, but my own experience has led me to not always agree with his conclusions. His main mission is selling his services, so like any salesman's claims, one must trust but verify.
 
just because you buy a factory engine don't mean crap....

seen one continental with a through bolt laying in cowling after flight from anchorage area to naknek.. with maybe 3 or 4 hours on it....
 
Cylinder replacement—and especially
replacement of multiple cylinders at once— is a procedure that needs to be executed perfectly.
Click to expand...

pretty much anything we do needs to be done perfectly......

crazy article....
 
wireweinie said:
The torque is done wet or dry as spelled out in the maintenance manual.

I think the author needs to come up here for a season or two and try to explain these claims. Apparently we are extremely lucky. Replacing a cylinder is just a maintenance item.

Web
Click to expand...
Good answer, and what I always thought, but I’m not an A&P, and this article left me wondering if I would ever want a cylinder pulled for a pre-buy for instance.
 
It's a miracle airplanes were able to stay in the air before Mike Busch and Tempest spark plugs came along.
 
I wondered what kind of response this one would get. I only do small Continentals, and most of those on Cubs do not have through bolts. We have a 90 going together next week - I will suggest the double torque wrench idea.

I often fix exhaust valves without honing - only thing I do is check valve lash, if it is a different cylinder. Never a problem.
 
Mike Busch has signed one log book in his life, his own. He started touting his stuff on Facebook a few years ago. He doesn't do as well in an open forum with a lot of mechanics with years of real world experience. Now all he posts are funny mems and links to his old articles. Like Joe posted, he is a salesman selling his service of over seeing the maintenance of your aircraft.
 
we got that in the ag world also, all the grain experts have never sat in a combine or know which end the grain goes in. or a nickels worth of anything depends on there expertise. this spark plug deal makes me think about beef, we have to take all these beef quality assurance and packer assurance tests here in the u. s. and all these experts write articles on how this works, yet they import hundreds of thousands of lbs from 3rd world countrys were most dont even know how to use a pencil. moral of the story, its just the way news is today, use to get opinons on both sides of a story, now its just one side and you have to decide if you want to believe it or not. no big shake.
 
one thing ive done right or wrong is retorque the cylinder nuts after 50-100 hrs when it works out, if this is right or wrong i dont know but i do it on the very few times ive messed with cylinders. just to check. is this a good thing?
 
So What is his recommendation on big bore Continentals, factory reman when the first cylinder is due... got to wonder just how marketable a 800-900 hour TBO engine will be?
 
Last edited:
tempdoug said:
one thing ive done right or wrong is retorque the cylinder nuts after 50-100 hrs when it works out, if this is right or wrong i dont know but i do it on the very few times ive messed with cylinders. just to check. is this a good thing?
Click to expand...

I’m not an A&P, but I have wondered if there would be anything wrong with that?

I noticed that all my cylinder studs have a red mark to ensure no loosening has occurred.
 
tempdoug said:
one thing ive done right or wrong is retorque the cylinder nuts after 50-100 hrs when it works out, if this is right or wrong i dont know but i do it on the very few times ive messed with cylinders. just to check. is this a good thing?
Click to expand...
I personally see nothing wrong with doing that.
It is not uncommon for a stud or long bolt to have some twist develop in them during the torquing process. Kind of why Lycoming calls for torquing both ends of a through stud.
Before the advent of modern stretch to yield fasteners in more modern industries which might get discovered in the airplane industry in a few decades it was a common practice to come back and give one more pull to check that the torque has not backed off on bolts or studs.

One thing to consider is after, say 100hrs is there is no longer and lubricant on the threads. I would go back to the fasteners much earlier, like the next few days being before the engine goes back in service.
I will add that if 50hrs later you go for a check and find a fastener that needed a turn, I would try to find out why as well as to be grateful you found it.
 
MoJo said:
I noticed that all my cylinder studs have a red mark to ensure no loosening has occurred.
Click to expand...
Common misconception. That is NOT what that torque seal lacquer is for. That putty is to be referenced only during installation so the assembler can keep track of what items have been torqued, and which have not. Once the engine is returned to service the paint marks are irrelevant and should not be relied upon for operational inspections.

I have seen many newbies and homebuilders use inspection putty like drunken sailors for what could only be cosmetic reasons. They interpret these lacquer dots as a professional look rather than the place mark tools they are designed to be.
 
Last edited:
tempdoug said:
one thing ive done right or wrong is retorque the cylinder nuts after 50-100 hrs when it works out, if this is right or wrong i dont know but i do it on the very few times ive messed with cylinders. just to check. is this a good thing?
Click to expand...

The proper way is to retorque about 24 hours after the initial torque. This is clock time, not engine operation! Torque it today, and then retorque tomorrow! It is surprising how much the case and studs relieve overnight and the nuts loosen.


Sent from my iPhone using Tapatalk
 
Is that general practice? There's nothing in my Lycoming overhaul/maintenance manual that says to re-torque after initial assembly.
 
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