Suspected Broken Oil control ring

[RLCarter]

Not a big fan of the ring flush, all the crap (carbon/coke) goes into the sump and not all of it comes out the drain. I understand MBs concern about pulling cylinders, but I believe too many believe it will be followed by a catastrophic failure…. A cylinder(s) installed CORRECTLY isn’t the issue, but he makes it sound like only overhaul shops or the factory can do it right. I really wish he would focus on the correct procedure rather than ones that failed due incorrect/incomplete procedures. Another area that isn’t mentioned when talking about oil consumption is the valve guides, particularly the intake guide…. My 4:30 am rant complete 

[Kelpro999]

D-Zolve 339 made by Solvent Kleene is my go to carbon removal Solvent. Beats every oil/fuel oil concoction I’ve ever tried. Judging by the amount of oil topside and still firing on that cylinder, stuck rings is a far stretch but worth a try.

Edited November 3, 2023 by Kelpro999

[Greg Ellis]

So, I was able to get with my mechanic.  We tried the ring flush and it seemed to pass by the piston and into the sump normally.  So we elected to pull the cylinder.  All rings including the oil control ring were fine.  Nothing broken.  The piston had an interesting mark which you can see in the photo.  The whole top of the piston was black with carbon except for this one spot that you see in the photo.  I have also attached a photo of the cylinder bore.  I have more if needed.  So we are sending the cylinder off for overhaul and we will see.

[PT20J]

Maybe the cylinder is just worn out. The piston looks like there has been a lot of blowby. I think the varnish on the skirt is caused by hot combustion gasses getting past the rings and oxidizing the oil. How many hours on it and can you make out any crosshatching or is the cylinder pretty smooth (it's hard to tell in the pictures)?

[Greg Ellis]

9 minutes ago, PT20J said:

Maybe the cylinder is just worn out. The piston looks like there has been a lot of blowby. I think the varnish on the skirt is caused by hot combustion gasses getting past the rings and oxidizing the oil. How many hours on it and can you make out any crosshatching or is the cylinder pretty smooth (it's hard to tell in the pictures)?

I cannot make out any cross hatching.  I would have to check the logs to get you info on time in service, etc…. I can check tomorrow.

[Pinecone]

So you did the ring flush, but did not see if it helped by flying it?

I can see cross hatching in the photo.

[skykrawler]

The rings probably aren't 'fine' - just not broken.   If that cylinder was IRAN'd within the last year it wasn't honed, piston cleaned and installed with new rings.  Why reinstall a cylinder without new rings?

Chances are other cylinders look the same.

 

[Kelpro999]

Knowing Cyl. Dia and ring gap will help diagnose.

[Greg Ellis]

An update on my cylinder.  I dropped it off at the overhaul shop this morning.  It is nice that they are only an hour away by car and I saved the shipping.  Anywho, while I was there the mechanic measured the cylinder bore and it was at its limits.  Also the rings were bad.  Visually they were okay.  But he took one and twisted it expecting it to break and it never did.  Just kept twisting on itself.  I was told that they eventually should snap but mine never did.  

So, they are going to have a cylinder ready for me next week.  Hopefully I can put this to rest and get back in the air just in time for my annual in January. 

[Fly Boomer]

1 hour ago, Greg Ellis said:

But he took one and twisted it expecting it to break and it never did.

Does that mean the ring has been overheated?

[Greg Ellis]

13 minutes ago, Fly Boomer said:

Does that mean the ring has been overheated?

That’s what I would have suspected but he didn’t say.  I should have asked but I was just kind of happy to possibly find a solutIon.  I’ll ask.  Though my EDM 900 never showed any issues of overheating or any other problems.

[PT20J]

Maybe the rings lost their seal due to the cylinder being worn out and the blowby is what overheated them causing them to lose their temper. 

[jetdriven]

Just be careful with this guys, I had a client whose oil ring broke and he swallowed up 7 quarts of oil in 40 minutes on one cylinder
 

[ragedracer1977]

Can someone explain what’s going on at the top of the cylinder? It looks like a big chunk corroded off above the intake valve and then it looks like a hole to the 7 o’clock of the exhaust valve. 
 

how did they replace the exhaust valve without pulling the cylinder?

[Kelpro999]

12 hours ago, ragedracer1977 said:

Can someone explain what’s going on at the top of the cylinder?

Looking at carbon and lead deposits flaking off 

[M20F]

On 11/10/2023 at 11:54 PM, PT20J said:

Maybe the rings lost their seal due to the cylinder being worn out and the blowby is what overheated them causing them to lose their temper. 

They didn’t lose their seal, they were making compression and no leaks noticed.  Personally I find the level of oil consumed beyond a ring issue (especially rings making compression).  Certainly something wrong with the cylinder but don’t think the rings were the main cause of consumption. 

[PT20J]

51 minutes ago, M20F said:

They didn’t lose their seal, they were making compression and no leaks noticed.  Personally I find the level of oil consumed beyond a ring issue (especially rings making compression).  Certainly something wrong with the cylinder but don’t think the rings were the main cause of consumption. 

Clearly the rings weren't sealing well but it may not be the ring's fault (at least before they lost their temper); it's probably that the barrel is just worn out and maybe out of round. The rings are at the top of the cylinder when you do the compression test, but most of the oil loss would be as the piston travels up and down the barrel. Also, an oily cylinder will often have great compression because the oil seals the ring barrel interface during the test. It's just another reason why compression tests are not a definitive indication of overall cylinder health.

[Bolter]

On 11/10/2023 at 11:14 AM, Greg Ellis said:

An update on my cylinder.  I dropped it off at the overhaul shop this morning.  It is nice that they are only an hour away by car and I saved the shipping.  Anywho, while I was there the mechanic measured the cylinder bore and it was at its limits.  Also the rings were bad.  Visually they were okay.  But he took one and twisted it expecting it to break and it never did.  Just kept twisting on itself.  I was told that they eventually should snap but mine never did.  

So, they are going to have a cylinder ready for me next week.  Hopefully I can put this to rest and get back in the air just in time for my annual in January. 

How did you establish which cylinder was consuming all the oil?  Or the reverse question, how do you know all the other cylinders are not part of the problem?  Did I miss that there was one cylinder with low compression or other outstanding measurement?

-dan

[Bryan G]

5 hours ago, Bolter said:

How did you establish which cylinder was consuming all the oil?  Or the reverse question, how do you know all the other cylinders are not part of the problem?  Did I miss that there was one cylinder with low compression or other outstanding measurement?

-dan

I had a high oil consumption all of the sudden, shop pulled the bottom plugs and my #4 was covered in oil. They also borescoped, but that’s how they knew which one. Stuck oil ring, repaired at LyCon and it’s running great again.

Of note, all my cylinders were 76+ compression. #4 was 78/80 with the stuck ring and high oil consumption.

[Greg Ellis]

11 hours ago, Bolter said:

How did you establish which cylinder was consuming all the oil?  Or the reverse question, how do you know all the other cylinders are not part of the problem?  Did I miss that there was one cylinder with low compression or other outstanding measurement?

-dan

What was missed is the fact that the number one cylinder was pooled with oil and both upper and lower spark plugs were wet.  I showed photos earlier.

[Greg Ellis]

11 hours ago, PT20J said:

Clearly the rings weren't sealing well but it may not be the ring's fault (at least before they lost their temper); it's probably that the barrel is just worn out and maybe out of round. The rings are at the top of the cylinder when you do the compression test, but most of the oil loss would be as the piston travels up and down the barrel. Also, an oily cylinder will often have great compression because the oil seals the ring barrel interface during the test. It's just another reason why compression tests are not a definitive indication of overall cylinder health.

When I took the cylinder back, the shop did a quick measurement and as I said earlier, the bore was at its maximum limit.  They called me later after actually doing close inspection and the bore was also out of round.

[Mooney-Shiner]

5 hours ago, Greg Ellis said:

When I took the cylinder back, the shop did a quick measurement and as I said earlier, the bore was at its maximum limit.  They called me later after actually doing close inspection and the bore was also out of round.

So the shop eventually determined that the cylinder was unairworthy (despite initial positive assessment)? What are you going to do with it? Re-plate with nickel or chrome and reinstall? Or replace with new?

Thank you for keeping us updated 

[Greg Ellis]

23 minutes ago, Mooney-Shiner said:

So the shop eventually determined that the cylinder was unairworthy (despite initial positive assessment)? What are you going to do with it? Re-plate with nickel or chrome and reinstall? Or replace with new?

Thank you for keeping us updated 

I am replacing it with a new cylinder.

[Mac80]

Thank you for posting this.