How to R&R cylinder on Lycoming

[Dan Thomas]

Not quite sure whats going on in the 3rd pic towards the base of the cylinder.

That's the bottom of the ring travels. You can see where each ring stops. The most wear is where all the rings travel, the least is where only the top or bottom rings travel, at the top and bottom of the travel range.

During ground-running moisture can build up between the piston and cylinder walls. After shutdown, this moisture causes corrosion of the cylinder wall, pitting it and reducing the ring contact area. The rings then eat away at the cylinder wall, and leave a sharp ridge at the bottom of the ring travel. That ridge chips away at the aluminum piston pin plugs that are designed to center the pin by running on the cylinder wall. You start finding aluminum ships in the filter. Just one more way of shortening the life of an engine.

Some old engines had five rings: three above the pin, two more beneath it. This moved any ridging below the pin button travels and avoided chipping the buttons.

The piston pins in both 1 & 2 were about the same. Perhaps slightly more pressure was required to start movement on #1. This is the first time I have removed a piston pin so I don't have a point of reference.

Those pins float in both the rod and piston. They aren't pressed into the rod as was common with auto engines. Only if there's serious varnish buildup on the short sections of pin between the rod's bushing and piston bosses will you have some shoving to do.

 

[FORANE]

That's the bottom of the ring travels. You can see where each ring stops.

I was referring to the seemingly random scuffs just outward of the ring travel limit.

Any idea what they used on the pins? There was an off white milky substance on the pins.
The assembly manual advises STP and 50w oil mix if I am not reading it incorrectly.

 

[Dan Thomas]

I was referring to the seemingly random scuffs just outward of the ring travel limit.

Those nice straight wide lines are from the piston pin buttons. Other scuffs are probably from carbon loosened from the ring grooves, marking the cylinder walls as you worked the piston out of the cylinder. Carbon is hard stuff.

Any idea what they used on the pins? There was an off white milky substance on the pins.
The assembly manual advises STP and 50w oil mix if I am not reading it incorrectly.

That would work fine.

 

[Gary Ward]

I stopped using STP in the 80s. Nasty to use while building an engine.
Reg motor oil on the wrist pins.
ONE drop of oil on the piston skirts and no oil on the rings or cylinder walls.
WD40 on the piston rings and cylinder walls and not much of it.
I have rebuilt a few hundred blown hemis and many other street, work engines and my own 0-320 with only WD 40 on the rings and cylinders. I didn’t leave the engine sit around for months.

Defiantly don't use motor oil on the rings. All that does is create carbon and burnt oil on your new rings and dirties up the ring grooves on your new engine. More importantly it pro longs how long it takes for your rings to seal up. They may not seal up at all with motor oil. With STP mixed in you are making it even harder for the rings to seat right away on start up.
I shipped out that wire UPS on Weds this past week.

 

[Magman]

To my knowledge no one has mentioned “ Choke” or “ Straight Bore”.

This is important when checking ring gaps.

There is no ALWAYS. Or NEVER with aircraft engines.

Don’t rely on the “ Big Guys” to necessarily do this correctly.

This is what Service data is for and is the responsibility of the

Installing Agency to verify.

Not a big deal; just very important.

 

[FORANE]

Oops, put the cylinders on today. Went by the manual. STP and 50w oil mix used on rings, cylinder walls and pins.

Checked ring gap at a piston depth into the cylinder as per a mostly cfi / licensed a&p but doesn't do a lot of maintenance. He works at our airport, attends our families church and graciously offered to assist us.

 

[FORANE]

Update on my mechanic. He's still missing, but they caught the other SOB last night.

 

[Gary Ward]

Any updates on your missing mechanic?

How did your cylinder swap go?
Did the rings seat and what is your oil consumption rate?

 

[Ed Haywood]

Not a happy ending. Hopefully TN gets their death penalty sorted out.

Deputies: Missing man was murdered by escaped inmate caught in Upstate

Deputies said an inmate who escaped custody in June has now been charged in connection with the homicide of a missing man.

www.foxcarolina.com

 

[FORANE]

Any updates on your missing mechanic?

How did your cylinder swap go?
Did the rings seat and what is your oil consumption rate?

Hey Gary. Cylinder swap went well. It wasn't as challenging as I suspected having never done it before. I think the rings have seated. CHT's have come down from an initial high of 420 immediately after takeoff and 405 in cruise to 405-410 after takeoff in climb and 385 in cruise. I have noticed the new cylinders are running much higher EGT's then the older #3&4 cylinders. Also noticed the new cylinders run CHT's around 360 in cruise full rich at 9000 or so. I suspect I have an induction leak in the new cylinders.

The intake tubes have the http://www.sdsefi.com/sdsaero.htm intake flanges. I didn't change the viton intake gasket o-rings. Perhaps I caused a leak there. Planning on replacing with new and seeing if that makes a difference.


Oil consumption is down to about a quart every 5-6 hours now.

Regarding my mechanic, Victor Birchfield, sadly as reported above we hear he was murdered. I don't believe it has been published yet but I hear the body they found was his. I heard the inmate stabbed him for his vehicle and dumped the body near Butler TN. Apparently before the body was found and recovered the bears found him. Victor was a good guy. He will be missed by many.

 

[Domenick]

Not a happy ending. Hopefully TN gets their death penalty sorted out.

Ghastly. Sorry for his, the family's, and your loss.

Birchfield was reported missing on June 21, the day after Fletcher walked off work detail at the Carter County Detention Center in Tennessee.

I wonder what Birchfield was in jail for that he was allowed on a work detail.

 

[Gary Ward]

Hey Gary. Cylinder swap went well. It wasn't as challenging as I suspected having never done it before. I think the rings have seated. CHT's have come down from an initial high of 420 immediately after takeoff and 405 in cruise to 405-410 after takeoff in climb and 385 in cruise. I have noticed the new cylinders are running much higher EGT's then the older #3&4 cylinders. Also noticed the new cylinders run CHT's around 360 in cruise full rich at 9000 or so. I suspect I have an induction leak in the new cylinders.

The intake tubes have the http://www.sdsefi.com/sdsaero.htm intake flanges. I didn't change the viton intake gasket o-rings. Perhaps I caused a leak there. Planning on replacing with new and seeing if that makes a difference.
View attachment 132120

Oil consumption is down to about a quart every 5-6 hours now.

Regarding my mechanic, Victor Birchfield, sadly as reported above we hear he was murdered. I don't believe it has been published yet but I hear the body they found was his. I heard the inmate stabbed him for his vehicle and dumped the body near Butler TN. Apparently before the body was found and recovered the bears found him. Victor was a good guy. He will be missed by many.

So sorry for your loss and for his family. That is terrible and tragic.
Yes always new gaskets and o rings whenever you take anything apart and put it back together.

 

[FORANE]

Update on my engine since replacing cylinders this year...

This summer I replaced cylinders #1 & #2 on my Titan x-340 due to low compression. I installed new Lycoming 05K21423-A cylinders. We've probably put over 50 hour on it now. CHT's initially peaked at 420 but relatively quickly came down and are now peaking below 400; cruise CHT's are running 365 or so on the new cylinders now.

On the last couple flights I have suddenly had significant oil on the belly even extending up the rudder. I rotated the prop through and could hear some air escaping the oil fill tube. So, I thought it developed blow by. I checked compression; all cylinders are high 70's / 80. I tried running a tube from the oil fill tube into a water jug while pressurizing the cylinders with 80 psi; no bubbles came out of the tube. I borescoped the cylinders and all looked good.

I cleaned the engine with degreaser and found the leak.

Look at the oil coming from between the banana plate and cylinder base.
What would cause a leak at the cylinder base as seen in this pic? That oil formed in just 2 minutes running the motor; it's losing 1 qt/4 hrs.
I checked torque on those nuts. They all were tight; re-torquing didn't seem to move the nuts much if at all. The 3/8 were torqued to 300 in lbs. The 1/2 nuts were torqued to 600 in lbs.

I'm presuming that cylinder has to come off and a new o-ring placed. Do the studs have to be changed? Why did this occur and what can be done to prevent it from happening with the new o-ring?

 

[Dan Thomas]

It might be a cylinder base seal, but there are some other things, too. The Lyc direct-drive overhaul manual has this to say on page 6-21:


Those shims keep the plates from resting in the radius between the cylinder barrel and base. If in the radius, they would work their way away from barrel, and the hardware would loosen.

Also on 6-21:

And on 6-22:




If the hardware is not properly tightened, the crankcase halves can move apart at the bearing saddles and let oil into the through-stud bores, and it trickles out as you see there. In some engines there are seals around those studs at the crankcase parting faces. Pages 7-14 and 7-15:



I would start with making sure those plates are properly located, and retorquing everything as per the manual.
https://www.expaircraft.com/PDF/Lycoming-OH-Manual.pdf

You might want to see the parts drawings for your X-340, and the assembly manual, if there is one.

 

[FORANE]

It might be a cylinder base seal, but there are some other things, too. The Lyc direct-drive overhaul manual has this to say on page 6-21:
View attachment 135350

Those shims keep the plates from resting in the radius between the cylinder barrel and base. If in the radius, they would work their way away from barrel, and the hardware would loosen.

Also on 6-21:
View attachment 135351
And on 6-22:

View attachment 135352

View attachment 135356
If the hardware is not properly tightened, the crankcase halves can move apart at the bearing saddles and let oil into the through-stud bores, and it trickles out as you see there. In some engines there are seals around those studs at the crankcase parting faces. Pages 7-14 and 7-15:
View attachment 135354
View attachment 135355

I would start with making sure those plates are properly located, and retorquing everything as per the manual.
https://www.expaircraft.com/PDF/Lycoming-OH-Manual.pdf

You might want to see the parts drawings for your X-340, and the assembly manual, if there is one.

Thank you for your feedback Dan. I appreciate it.
This does appear to be a cylinder through stud leak.

Continental service bulletins:
https://continental.aero/pma-service-bulletins/
SIL007
https://continental.aero/service-bulletins/pma/sil007.pdf
VII. CYLINDER REMOVAL AND INSTALLATION
Reference the latest revision of the OEM’s ICAs (see Table 2).



60294-7 (like you posted) says on page page 140/146 (which we followed):


I didn't know about those shims. We missed that.

I did do a wet torque and in the order like you posted above.

A web search reveals others with the same issue:

Oil leak on Cylinder through stud. - The International Cessna 170 Association

and an unapproved fix: Or, you can simply remove the nut, clean the stud with electronics cleaner, put a tight-fitting O-ring on the stud, apply a bead of Permatex gasket sealer (Non Hardening is best) and torque the nut back down. I've seen several successfully sealed with this technique.

It doesn't appear the stud o-ring is replaceable without major surgery.

 

[Dan Thomas]

...and an unapproved fix: Or, you can simply remove the nut, clean the stud with electronics cleaner, put a tight-fitting O-ring on the stud, apply a bead of Permatex gasket sealer (Non Hardening is best) and torque the nut back down. I've seen several successfully sealed with this technique.

Got to watch that. Anything that introduces any chance of movement between that cylinder base and the case is a recipe for stud failure. Guys have used RTV on the base, and blown cylinders off. In your case, there could be movement between the base and the nut, equally bad.

 

[FORANE]

Got to watch that. Anything that introduces any chance of movement between that cylinder base and the case is a recipe for stud failure. Guys have used RTV on the base, and blown cylinders off. In your case, there could be movement between the base and the nut, equally bad.

Yes, I have read this is a concern; thanks for pointing it out.

Lycoming service instructon 1290f addresses the exact issue I think I'm having of through stud oil leaking. It's on VAF available for download. Only problem with that service instructon is it applies to wide deck Lycoming; mine is a narrow deck.

I want to do the right repair and not just throw a bandaid at it. Just not sure what the right thing is yet...

 

[Bell206]

I want to do the right repair and not just throw a bandaid at it. Just not sure what the right thing is yet...

Do you know if your x340 has free thru bolts with internal orings or without?

One thing you may also want to check for is cracks at the thru bolt area. Its something I've always done when there was a leak in that area. Curious, did you retorque the other 2 cylinders after you replaced 1 and 2?

For more input, perhaps contact Titan support at TCM?

 

[Chip Sylverne]

It's CYL !

Sorry, being a writer, I can't help myself. Otherwise great posts as usual.

AKA a jug. And autocorrect won't eff with it.

 

[FORANE]

Do you know if your x340 has free thru bolts with internal orings or without?

One thing you may also want to check for is cracks at the thru bolt area. Its something I've always done when there was a leak in that area. Curious, did you retorque the other 2 cylinders after you replaced 1 and 2?

For more input, perhaps contact Titan support at TCM?

Don't know if through bolts.
I did think of cracking and looked as much as I could without cylinder removed...
Did not retourque cylinder 3/4.
I am planning on contacting James Ball with Continental this evening.
I'm assuming at least that cylinder will need to come off again.
I'll ask James Ball if they are thru studs and about possible stud replacement with oversized studs as well as any thread sealant.

Is there a recommended stud removal tool for Lycoming cylinder studs?

 

[Gary Ward]

Don't know if through bolts.
I did think of cracking and looked as much as I could without cylinder removed...
Did not retourque cylinder 3/4.
I am planning on contacting James Ball with Continental this evening.
I'm assuming at least that cylinder will need to come off again.
I'll ask James Ball if they are thru studs and about possible stud replacement with oversized studs as well as any thread sealant.

Is there a recommended stud removal tool for Lycoming cylinder studs?

This is the stud tool that I would recommend, but I have never messed with any aircraft engine studs. Our racing engines everything was held together with studs.

 

[hindsight2020]

ah yes, studs. When mine failed inflight, no options were afforded to me to replace without opening the case, heck nobody would even entertain an IRAN job (low margin work). Since I didn't have the tools, time, rented willing signatory (was a certified) or workspace to tackle the job a la @Jim K , stage right for me.

You being EAB, you could probably tackle the job and save some money to stay in the game, recognizing it's that cylinder replacement torque unload/perturbation that probably loosened the whole thing in the first place.

The irony being, technically these loosening affairs are maintenance induced failures. Gotta break it to fix it, fantastic engineering... for when coke/sodas only cost a nickel and working people could afford housing. Aaaand digressing.

I wish you luck and low costs on this quest. I'm rooting for ya!

 

[Bell206]

Is there a recommended stud removal tool for Lycoming cylinder studs?

I'm sure there is but never saw one. I'd start with your call to Jim Ball first (I thought he had retired) and give him the 411.

But just to throw out there, if this were me, I'd pull both cylinders you installed and check everything very close with a bright light and mag glass. Then come up with a plan based on what Ball says and what you find. If there is a separate OH manual for Titan X340s like the CC340s, you may want to invest in that as well. Hard to make any recommendations based on what you've seen. And if any of this is a bit outside your comfort zone definitely see if you can get some assistance. Good luck.