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  #11  
Old 10-03-2012, 07:31 PM
Darren S Darren S is offline
 
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Can a piston ring be broken and not cause any scoring of the cylinder walls?
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  #12  
Old 10-03-2012, 08:59 PM
aerhed aerhed is offline
 
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Yes it can. If you are still at a quart in 20-25 though I think a busted ring is unlikely. What kind of cylinders? Chrome, steel, nickel?
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  #13  
Old 10-04-2012, 10:01 AM
Darren S Darren S is offline
 
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Well, from further research it seems like the oil ring maybe broken. How bad, who knows ?

I am still doing my San Francisco trip tomorrow which will be a 14 hour round trip. With the oil consumption at a minimum, the cylinder walls not scored up, compression normal, performance the same, recent oil change.....I have no reason to ground the plane.

I will pull an oil sample again when I get back and continue to monitor the bottom oily plug.

Will it go away, probably not. From what I've been told, pulling a jug and changing rings isn't too hard or $$.

I'll keep the forum update as to my findings. thanks to all for the help.

Darren
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  #14  
Old 10-06-2012, 08:51 AM
Darren S Darren S is offline
 
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Location: Canada
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Default Further findings

Ok I'm not done with this post yet. I flew down from Calgary to San Francisco yesterday. From all indications the engine ran fine.

I did in flight mag checks and all was fine, even at 25 degrees LOP.

I had a long taxi and wait in Spokane for departure and my #4 bottom plug started to foul. I know this because during my wait I did another mag check and the EGT started to drop not rise, telling me the plug ain't firing.

I said screw it and took off. In flight again mag checks were fine. After 7 hours and engine cool down the oil is clean an down about 1/3rd of a quart. Importantly it's clean and not black.

The new stuff: I looked under the plane and the belly is a bit oily from the breather tube (normal), but on the pilot side of the belly there are oil streaks coming from under the cowl. The engine is spitting oil onto the firewall and it's leaking down under the cowl. This is the same side as #4 cylinder.

I cleaned the belly before leaving home.

So here's my question:

What will cause a spike in Chromium and iron on an oil analysis, foul a bottom plug yet not affect compression, not show up on horoscope, not cause oil consumption or rapidly darkening oil and cause the firewall to get splattered with oil?

Maybe only God knows. Anyways whatever opinions are out there I'd love to hear them. I'm off to Alcartaz with my daughter(faithful co-pilot)

Darren
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  #15  
Old 11-03-2012, 07:16 PM
Darren S Darren S is offline
 
Join Date: Apr 2009
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Default Follow up

I've read lots and lots of threads and there are times when a thread contains the same issue I'm dealing with. I read and read only to find there was no conclusion to the saga, or none posted. So since I started this thread and another similar one, I will give the conclusion to the saga in the hopes that it will help someone....someday.

To backtrack. My original issue is this. Engine is an IO-360, Superior, 750 hours, regular use. It was oil fouling the bottom plug of #4 cylinder. Not huge amounts but more than the other bottom plugs. I did a mag check one day and the plug wasn't firing. I pulled it and it was oil fouled. Then my most recent oil analysis report came back and it showed 12 times higher Chromium (normally 5 ppm and it was something like 70 ppm) and elevated Iron (normally 25 ppm and it was 62 ppm).

I freaked out and started reading and posting questions. The plane ran fine, compression was fine, started fine, no metal in the filter, no excessive oil burn (burns about a quart in 30 hours).

I came back from my San Fran trip and pulled another oil sample. Still elevated Chromium and Iron after 16 hours.

I decided to pull jug #4. Not a simple task !!! The baffles have to come off, a bunch of stuff to disconnect and special wrenches required to pull the base nuts at the bottom of the jug. Much easier said than done !! Also, we had to get the piston off by pushing the piston plug out. EASIER SAID THAN DONE. I'll spare you the gory details of how we did this, but suffice to say we damaged the piston and the copper bushing on the connecting rod. Those had to be replaced.

I was looking for a broken ring, scored cylinder something. Nothing was obvious. There was some wear at the top of the jug where the top compression ring stops and changes direction, and a little wear from the piston skirt touching (perhaps from a cold start). But no smoking gun.

I was disappointed and glad at the same time. They honed the cylinder, put new rings, new piston, new bushing on the connecting rod, checked the valves and gave it back to me.

I hired and AME to help me put the jug back on. I wrecked enough stuff taking it off and didn't want anything to go wrong with the re-install. He brought by his fancy tools and his digital torque wrench and helped me. Then I spent the next two days putting the baffles back together and cleaning up stuff under the cowl.

So....... was it worth it?? NO!!! or at least I don't think so. I did learn how to take a jug off and put it back on, I did see the guts of my engine, learn how to use some new tools. I got to see what my finger looks like with safety wire run right through it !! and how to make a bandaid out of blue shop cloth and masking tape

Here's what I should have done. Not panic first of all. With elevated numbers in the oil analysis, watch the trend. The trend can only be developed with more time and oil samples. With good compression (all cylinders were 76/80 and above), no metal in the oil, no excessive oil burn.......leave it and fly the darn thing.

Sample every 25 hours if need be. Oil is cheap compared to what I did. If the numbers rise and then stay the same for several hundred more hours.....so be it. As long as the compression is good, no metal in the filter etc.... just go fly.

These are parts per million we are talking about, don't freak out.

If however the trend is that the a particular wear metal goes from 5 ppm to 70 ppm to 250 ppm to 600 ppm in subsequent 25 hour oil changes, well then you need to start checking into what the cause is.

Finally, possible causes. From what I can gather. The rings are suppose to turn through out their life. Sometimes they can align. This could cause oil to escape and foul a plug, this could also cause some extra wear if they get stuck. The solution, you guessed it, keep flying, observe and see if the problem resolves itself. The rings may "unstick" themselves.

I have only flown 3 hours since the new jug was put on. I was told to run regular oil and fly WOT for 5 hours. I take off and keep the power at 80%. I burn more gas but it's fun flying fast

Hope this helps someone someday.

Darren

Last edited by Darren S : 11-03-2012 at 09:11 PM.
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  #16  
Old 11-03-2012, 07:29 PM
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Vlad Vlad is offline
 
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Good info thanks for sharing Darren.


I am sure this was a slip of keyboard
or it really burns that?

Quote:
.... no excessive oil burn (burns about a gallon in 30 hours).
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  #17  
Old 11-03-2012, 08:48 PM
gongreg gongreg is offline
 
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Location: S?o Paulo Brasil
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Default A quarter?

I think he meant a quarter every 30 hours.
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  #18  
Old 11-03-2012, 09:18 PM
Darren S Darren S is offline
 
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Funny Ok, I fixed the typo.
Yea, it's suppose to be a quart in 30 hours. Although a gallon in 30 hours works out to be about a quart in 7 hours which is kind of high I guess, but still lower than Lycomings cut off of a quart per hour
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