Do I need to be concerned about? Cylinder wall deposits/glazing?

[swisseagle]

Hello

Found this during a borescopie on a buddys engine:
- RV-7
- TMX-IO-320
- Built in 2010
- First run 2015
- 140h since new
- AVGAS only
- Cruise 50-55%
- Sensenich metal FP prop
- Recently 10-15h formation flying with slow partner, 28-32% power
- Compression is 77-78 @80psi
- CHT during the first 10 flight up to 425°F, then going down to below 400°F and now around 385-395°F @ TO and climb.
- Lycoming cylinder, light blue marked, seams to be Nitride-hardened cylinder barrels
Interestingly, when engine is cold, prop turned by hand, I can feel different compression strokes.
Two where strong, one a bit less, and one feels a bit weak. When engine is hot, this "differences" go away.

All the deposits are in the lower end, about 25% away from BDC.

Cyl 1:


Piston pin marks visible.

Cyl 2:


Cyl 3:



Cyl 4:


From where does this come from?

What to do?
- Continue flying the plane without risking something bad? All is fine?
- Fly max. one season and then take off jugs, hone and build up again?
- Stop flying immediately and take off jugs, hone and build up again?

Thanks alot!

Dominik

[jliltd]

If they are nickle cylinders it looks like the nickle is coming off. If they are Titan cylinders from that era be very careful and consider replacing them. Check ADs on Titans. If they are hardened steel it looks like general wear. Ask the owner if he has had an instance of very high CHTs in the past (like steep climbs, very lean mixture or combo thereof).

I just went through something similar on a 200hr first run 360 and based on my experience I would be tempted to pull and inspect the affected cylinders immediately. It's a bit costly now but much cheaper than a full TDI or worse later.

[swisseagle]

Added more info about CHT and cylinder type in the first post.

[TShort]

Originally Posted by RV8JD

The pics for Cyl #1 don't show, due to Google oddities.

I can see them all .... for now.

[bret]

One thought, compression is good, is oil consumption reasonable? I say run it, on the other side, those cylinders should not look like that with 140 hours. Have you done an oil analysis? that will show what is going on with those cylinders.

[F1R]

Send Dr. Mahlon R your photos in a PM.

If you are trying to find him he is post #7 in the "find this weird vibration thread "
http://www.vansairforce.com/communit...d.php?t=170636

[swisseagle]

Hello

The oil consumption is really low, less than one quart per 25 hours.

Two oil analysis done, all good, a bit of metals, but reducing. Lab say all normal for a young engine. Another sample on the way to the lab.

Savvy say all is fine, done the test flight they asked for.

[rocketbob]

Leave it alone!!

Definitely glazed but not very bad.

Keep an eye on piston pin plug wear.

[mahlon_r]

Looks like surface rust to me. If compression and oil consumption is good ,keep running it. Hopefully, you will wear the rust off before wearing the rings out. That is the most likely scenario. Keep an eye on the screen and filter every oil change for piston pin plug material. From the pictures, I don't think it is bad enough to cause any significant issues but checking the filter and screen carefully should prove out that theory.
Their appearance in not that abnormal for nitride cylinders that may have sat, not being used for a while. Nitride cylinders get surface rust pretty easily. Try to get an hour a week on the engine and it shouldn't get any worse.
Good Luck,
Mahlon

[swisseagle]

Hello all together

Thank you for the answers.

We will continue to use it as often as possible!

About the piston pin wear ... is it correct, that we can not do anything against it? I've made a few borescope sessions, and a few have piston pin marks and others not!?