Engine Trouble

[Nev]

John Bickham Regarding the oil leak from my Prop Governor, there was a bulletin about it from 2016. I had it serviced in July, and knowing what I know now I think that problem has been fixed. However the oil leak from the cylinder flange fitted neatly time-wise with the governor leak, so I attributed it to the governor not being repaired properly and didn't search further at that time.

We didn't find any evidence of paint or contamination between the cylinder flange and the crankcase. That area appears to be clean. Because of this we don't plan to remove other cylinders unnecessarily.

We did find very visible evidence on the outside face of the cylinder flange, and under the hold-down plates. It appears that this is probably the cause of the problem. Fortunately, thats easier to access and doesn't require the removal of the cylinder in order to check it. It does require the baffles to be removed, and the cylinder nuts to be removed so that the hold-down plate can be removed. So while it's still a PITA, it's a much preferable alternative to not checking it until the studs shear off. Not only does that make your day overly exciting, it can actually ruin your whole afternoon.

Regarding the through bolts (studs) - (and noting that I'm not an aircraft engineer) - they do go through the case, and hold opposing cylinders onto the case. So some of the cylinder studs are shorter and seat into the crankcase, and the through-studs are longer and screw in from one side. Once seated, each end is threaded and holds opposite cylinders in place. My understanding is that there is a concern because it may also affect the crankcase integrity. On mine, the side of the through bolt that sheared off was also the side that is threaded into the crankcase, so theoretically it shouldn't have affected the opposite side, but I'm well aware that I might be taking an optimistic view here too. We are currently in the process of ordering new studs for the whole #4 cylinder. We will also be removing and cleaning all of the other cylinder flanges.

[svyolo]

I have a similar engine from the same source, except I ordered rebuilt cylinders. Those cylinders came with a nice paint job, including the external flange. I see no sealant weeping out, but I also see no evidence of that cylinder paint being removed from under the plates. And the outside of the double plates also appears to have a thin coat of paint. According to that reference you posted, paint on the external cylinder flange probably isn't a good thing.

This is not an official source, nor do I endorse it. But I asked:

":When installing cylinders on a narrow deck Lycoming engine, it is advisable to remove the paint from the external cylinder flange before installing the doubler plate (also known as "banana plates" or hold-down plates). This practice ensures a proper fit and torque, as paint can interfere with the seating of the doubler plate and potentially lead to under-torquing or loosening of the nuts over time. According to discussions on aviation maintenance forums, the presence of paint on the flange can lead to issues with torque application and maintenance of the engine's structural integrity. Removing the paint helps ensure that the nuts can be properly tightened to the specified torque, maintaining the engine's reliability and performance."

[John Bickham]

Thanks for the update Nev. The report of no evidence of paint or contamination found between the cylinder flange and crankcase is a huge relief. I'm stepping back from the edge of the "cylinder pulling cliff". My cylinders don't have the hold down plates. I'm going seek some help and expertise on "checking torque on cylinder base bolts". I am a Mike Busch fan too. I think I will start another thread on addressing oil leaks in the maintenance section. I know it has been a challenging time for you.Thanks again.

[gregc]

Personally if I suspected an issue with cylinder hold down fasteners I would get help from someone with a lot of Lycoming overhaul experience. I lean to the Mike Busch school of thought on this subject. This is an area where the chances of making it worse are significant.

https://www.savvyaviation.com/wp-content/uploads/articles_eaa/EAA_2014-06_cylinder-work-be-afraid.pdf

I don't know of a foolproof method to check the torque on a previously fastened nut. I have read about different approaches (on-torque, off-torque, marked fastener) but they all depend on assuming the previous coefficient of friction hasn't changed as well as good tool access, a recently calibrated torque wrench etc.

The Lycoming procedure for tightening cylinder fasteners is quite specific in both process and sequence. To me, this feels like something that requires some experience, I certainly wouldn't trust my first attempt!

[Nev]

Thanks Greg. I'm with you on the Mike Busch school of thought - I had hoped to make it through at least a couple of thousand hours without pulling cylinders. In order to inspect the remaining hold down plates we won't actually be removing those cylinders, just the plates themselves, (although that point might be somewhat academic). Fortunately we've got some very experienced Lycoming aircraft engineers (I think in North America you would call them mechanics) here to advise us, and also to do the work.

[Battson]

Excellent comments Greg

[John Bickham]

Since Mike Busch was mentioned. This is the point that Whee was making. Continental engine but same concern.

EAA_2013-04_a-little-dab-ll-do-ya-in.pdf

[Nev]

Since Mike Busch was mentioned. This is the point that Whee was making. Continental engine but same concern.

[ATTACH]n93189[/ATTACH]

That's a very sobering read and makes it clear that the use of paint or sealants when mounting the cylinders is a known issue and not permitted. The last paragraph sums it up with the clear warning :


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[TJ_Slice]

This whole thread really has me contemplating my engine choice. While I know any engine can fail, but I like the peace of mind of having a new engine.

Something like this would surely have an impact on my wife, and I doubt if she would ever feel comfortable flying with the same engine or airplane again.

I would say I am leaning toward going new, and just biting the bullet on cost and acquisition time.

I could divert some of the money planned for an IFR panel, and build a VFR only airplane. I may also be able to absorb the cost over the build time and still get an IFR plane. I would likely plan and wire for the panel I eventually want, and not what I start with, so that would make upgrading sometime in the future much easier.

The big question is whether the peace of mind is worth it? I think I am there.

[Battson]

To be fair, experimental aircraft are not losing cylinders left right and centre. There's probably 10,000 of these engines running globally, year in and out, without cylinder stud issues. The chances of this happening must be rather remote.

Even the biggest names in the business have "Friday afternoon" jobs where things go wrong. It's just a lower probability, but hard to say how much lower... Is that unquantified benefit worth paying between 2x and 4x the price, well that's a personal decision.

Ultimately you have to trust an experienced professional, to do a good job.
The more engines they do, the more confident you can be, but the reliability rates of certified engines aren't that much better than experimental engines, when you considering that the experimental stats includes all comers.

[gregc]

It's a personal call and peace of mind is obviously worth a lot but - are new engines safer/more reliable? Maybe, probably, I don't know. Unfortunately I have never been able to find data that demonstrates unequivocally that a new engine is 'better' than a rebuilt engine. Or that a rebuild is better than an overhaul. Or that a certified engine is more reliable than an experimental. It seems that this kind of data is simply not collected or is never published. My take-away from this thread is that it is a reminder to take every opportunity to look over and listen to the engine you are flying behind. They often give us clues about their overall health and rarely fail without any warning whatsoever. Even Nev's major problem gave him time to safely land the plane. My second take-away would be to strive to do as well as he did managing a major failure. That's something I can control and surely could get better at.

[Steve W]

35+ years ago I had experience with a Saratoga going down in the bush outside Gander NL when I was working in the province. Not me flyin and fortunately no injuries. Was at night though and there is a reason they call the island of Newfoundland the “Rock”. Amazing job by the pilot who was delivering the plane from the factory to Europe. The new engine had a large hole in the side of the crank case.
I have heard similar stories on both sides of the fence with buying new or used. Personally, if all of the reciprocating parts are NDT’d, new cylinders installed, and put together by a reputable shop, I have no hesitation to sit behind a rebuilt engine. They are made, assembled and operated by humans so……. new is no guarantee. Just sayin

[TJ_Slice]

In my heart, I know that to be true, but my head is getting in the way.

[John Bickham]

I'll just add one more YouTube video by Mike Busch. Ran across this one. So much to learn!

[Nev]

What an excellent video. Would be well worth the time to watch for anyone who has a rebuilt engine and is concerned about RTV / Paint being used on the cylinder flanges or crankcase halves.

[rkennell]

A friend and mentor, who scratch built a Mustang II and is now building a WagAreo clipped wing Cub, and I have had numerous discussion because of this thread and what Nev has experienced. In our last visit he related to me that his son, who is an A&P and AI with extensive experience with PW radials to turbines and most GA engines, was experiencing an increasing vibration in the Mustang over the last number of flights. The son suspected the prop and went through the prop balancing procedure and found the prop balance good. On further inspection of the Lycoming O-320 narrow-deck, he discovered one internal wrench nut missing and the other nuts loose on one cylinder. He then checked the nuts on all the cylinders and every one of them took torque to come up to specification. The son visited with another engine builder on the field who stated that he has seen the same thing on other narrow deck Lycoming engines that use internal wrench nuts on the cylinders. RTV/paint was not the issue in this O-320 or the other incidences that the engine builder has seen and it seems that the issue is limited to Lycoming narrow-deck engines that use internal wrench nut on the cylinders. The engine builder nor the son have seen cylinder nuts loosen on on the wide-deck Lycomings that use hex nuts when Lycoming procedures and torques were used. In our discussion we speculated that the hex nut may have more gripping surface then the internal wrench nut and the spacer plate on the narrow deck engines may contribute to the issue. I must emphasize, that is a speculative observation. After torquing the cylinders the engine ran very smoothly.

These are the takeaways for me from the son's discovery:

1: We all need to take notice of unusual vibration, oil leaks and investigate the cause. The son stated that it was less than 10 hours of flight between the start of the vibration and the discovered loose nuts.
2: The torques on cylinder nuts should be part of the condition inspection that we preform on our aircraft each year or at least every 100 hr.
3: It would be an interesting data point if forum users reported back to the forum what they find after checking torques. The reports should include the type engine (wide or narrow deck), type of cylinder nuts (hex or internal wrench) and the hours on the engine when checked.

I want to express my gratitude to Nev and others who take the time to share there experiences and knowledge on this forum. I have learned so much about building and flying. I have been a pilot for over 50 years and still find so much that I don't know. Thanks to you all.

[Nev]

The past 5 days myself and my mechanic Kevin have stripped the engine back and completed work required as a result of finding sheared cylinder studs and discovering paint on the cylinder hold down plates as per the Original Post. The first job after removing cowls, baffles, oil lines, air intake tubes, wiring etc, was to remove the #4 and #5 cylinders again, and replace the remaining studs on the #4. Two of the crankcase through studs also serve the #5 cylinder, hence requiring its removal too.

The next job was to systematically remove the hold-down plates of each other cylinder, clean them, and replace and torque them to Lycoming specifications. We pulled the oil filter again and were pleased to see it was free of any metal. I also removed the sump screen. It was free of metal, but did contain a small slither of red RTV - Kev tells me that using RTV to seal the crank case halves is not acceptable in NZ.

I also took this opportunity to replace the metal oil line clips with hose clamps (thanks Battson !) to hopefully eliminate small oil leaks in that area.

Finally, after a lot of work and down-time I hope that we've put these issues behind us and can go flying with the confidence in my engine that we need.

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[rkennell]

Nev, Thanks for the update. I was wondering how the repair was progressing.

[svyolo]

That pic looks like the banana plates themselves were painted. Is that the case? I bought rebuilt cylinders, and my cylinders are definitely painted, with no evidence the paint was removed under the plates. I don't see any evidence on mine of sealant or anything else creeping out from under the base of the cylinder/.case. Only at 40 hours.

[Nev]

Yes it is the hold-down (banana) plates that are painted unfortunately. It should be a metal on metal contact.

[Bissetg]

To my unqualified mind red RTV in the sump is concerning. I know when it was found in my sump it caused a high level of excitement and anxiety with my mechanics who were concerned about it blocking oil galleries.

As it turned out my engine didn’t last long enough for me to have to worry about it.

That you have RTV turning up in the sump after 400 odd hours is a concern I would think.

[Nev]

Yep I'm surprised that it's allowed in other countries.

[Bcone1381]

Photo Data below shows my cylinder hold down plates were painted on at least three faces. An IA looked at it, and called out the paint between the cylinder hold down plate and the cylinder nut as unsatisfactory. The paint will wear away over time and reduce bolt preload. My baffling and exhaust was removed yesterday with help and guidance from others more experienced than I yesterday. Waiting for the cylinder wrenches to arrive now.

The Sky Ranch Engine Manual is an outstanding book on Lycoming engines. It blends science and physics with airplane engines. Ch7 is titled Fasteners and Failures. It has a section on p.185 called Paint and Broken Cylinder Studs. The graphic below gives explanation of Batson's post #18 about bolt stretch, preload, and fatigue.

Nev & Grant, thanks for ratcheting up the safety of our hobby. It's not easy. You guys set a high standard....Industry best standard...for us. It's safer and I'm safer due to you guys reporting this.


Screenshot 2025-02-03 at 6.17.07 AM.png Screenshot 2025-01-31 at 3.11.54 PM.png

[Bissetg]

On the positive side.

What we/I have learnt from this thread is valuable.

1 contamination between metal surfaces that are torqued to a specific value is a no no unless an approved product and process is applied.

2 Torques should always be to specs.

3 any oil leaks/weeps or seeps should be investigated including checking TQ of associated fasteners.

4 Any under TQ sets up a fatigue cycle that will cause failure.

5 dealing with these things by preemptively checking is way safer, cheaper, and less stressful than dealing with the consequences of a failure. Read that again.

[Bcone1381]

On the positive side.

What we/I have learnt from this thread is valuable.

1 contamination between metal surfaces that are torqued to a specific value is a no no unless an approved product and process is applied.

2 Torques should always be to specs.

3 any oil leaks/weeps or seeps should be investigated including checking TQ of associated fasteners.

4 Any under TQ sets up a fatigue cycle that will cause failure.

5 dealing with these things by preemptively checking is way safer, cheaper, and less stressful than dealing with the consequences of a failure. Read that again.

The hold down plate clean-up procedure is completed. Data I gathered during the clean-up was.
-The plate face that marries with the cylinder had no paint on it.
-Bench inspection of nuts and plates showed that paint evidence (under magnification) under both bolt heads and outer faces of plates. So two layers of paint existed per bolt/stud joint.
-The following is not data, its feeling and unscientific logic. The feel of torque required for initial Nut removal indicated to me some preload was loss on some bolts. The shorter the stud the more clear it seemed. Not all, but not one or two. I believe all nuts were properly torqued when it was assembled. Then paint coating failed sometime after the torquing.

I built alone in my workshop for 7 years. Now I'm at an airport and have good relatioships with good people.

Ya know, I placed barriers for myself to perform this procedure, and good people came together in an interesting way to encourage hold off on beginning my test flying phase. Nev and Bissetg past experiences raised concern. I didn't test fly it due to the FAA safety inspector having issues with my airworthiness application. Then Nev Bailey's Post #54 had me investigate if paint existed on the hold down plates. A friend who is an IA looked at what I found the post #57 data point and did not agree with me that it was prudent to still do the test flying. Arborite here on this forum (LSA builder) and another GA hobbiest A&P offered there labor and collaboration to do the repair. They are giving up there time, a heated hangar and more. I tend to take a rosey viewpoint of things. "It will be okay" so I needed more data and know where to look for the data to make to tear it apart. People just lined up to help me.

Humanity and life is really quite fun when we collaborate like this. Its safer. Learning, growing, navigating risk together is pretty cool to experience. We can do more in life together. So maybe this post is here help repay a bit of the debt I owe to those who are helping me navigate the system.

[DBeaulieu]

Well said Brooks! My time within the EAB world over the past years has been similiarly remarkable in the same context of good people, assisting, advising, collaborating and making my experience so far a marvelous and interesting adventure.

[rodsmith]

That sounds like it was a good decision Brooks. I had the advantage of participating in my engine overhaul and remember my mechanic pointing out that there was and never should be any paint on those surfaces. I'm curious, what was the FAA inspector unhappy about with your application?

[Bcone1381]

The FAA...I made a data entry in the Engine Make and Modle data that autofilled onto the airworthiness application. I said "Reciprocating - Barrows" The inspector needed them to be Lycoming and IO-360 series. I did not make up reciprocating but I like that answer. I think the EAA instructions led me to say Reciprocating. I made up Barrows because at some point in the data entry process I could not get a model type that it accepted along side Reciprocating. I seem to recall I tried several versions of Not Applicable, but it took Barrows. I looked at it and thought "they might not like that but they'll see it and tell me what they need." and moved on with the data entry. I'm not too skilled with electronic computer stuff.