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Normal or not??

D

Darren S

Well Known Member
My Superior IO-360 has 775 hours on it. It has performed well and I do my best to take care of it by changing the oil regularly and leaning it out.

My #4 bottom plug, and only this one, gets a little oily a few hours after cleaning and gapping. I use Champion REM 40E plugs. Recently, after about 30 hours, this plug oil fouled bad enough that it didn't fire and the EGT went to zero on my pre-takeoff mag check. I put in a new one and all was well.

I assumed that the plug was bad, hence the wet look when I pulled it.

The other bottom plugs stay dry. A little carbon dust on them, but dry.

I had the compression checked and the cylinder boroscoped. Compressions were all 75-77 and all cylinders showed no scratch marks or grooves indicating a broken ring.

The engine runs fine, starts fine, no concerns other than this.

So, is this normal to see as the engine wears?

If there is blowby from the oil ring on the piston, why isn't the top plug oily also?

Thanks for any help on this issue.

Darren
 
Excess oil in the jug gets squegeed right onto the lower plug. Do you have steel barrels? If so, I would pull the cylinder and do a re-ring & hone. Good opportunity to spiff up the valves while you're at it. An oily cylinder always shows better compression than it should. You can often hold your compression check air on the jug a few minutes and after it blows out some oil your reading will drop a few pounds.
 
Would you consider this a flight safety issue ?

I'm leaning towards flying the thing for more hours, monitoring the situation, rotating the plugs every 25 hours instead of 50 hours, checking compression more than just at annuals.

Your thoughts about this approach?

Thanks for your help

Darren
 
I wouldn't be pulling a cylinder just yet

First thing I'd do is to check the resistance of the plug. Should be about 5K. If the resistance is way over that (and it wouldn't be so unusual if it were) the plug is not firing well (and there is the potential for damage to the mag).

Even if the resistance is okay, I might still replace the spark plug just to see what happens. I'm not sure which flavor of IO-360 you have, but I might be more inclined to use a UREM37BY instead of a REM40E. (Check http://www.proaeroengines.com/docs/4DEE02A5FFDBEB4C.pdf)

If all checks out there, check the ignition lead for that plug.

As for continued flying, if you haven't done the Lycoming "wobble test," you should. Also, although intended for brand "C", there's a lot of good useful info at http://www.tcmlink.com/pdf2/sb03-3.pdf for when it comes time to do compression & cylinder testing.

Dan
 
Similar problem

Darren, I had a similar problem in my -4. Compression remained good, but a plug would get fouled. It got worse, oil consumption also climbed. I got to the point where the last 2 - 3 flights on the engine I was going through a quart of oil per hour, and the plug would be fouled after every flight. We pulled the cylinder but didn't find anything amiss (maybe I needed a better mechanic). In my case we also found the cam had pitting on the lobes so I decided to scrap the engine and put in a new one from Aerosport Power.
 
OP says he put in a new plug and ignition is fine. Recheck the plug in awhile and if it is burning clean, it was a bad plug & you're okay. Otherwise its in the jug. If you can get an oil change between plug cleanings, I wouldn't call it a safety issue.....probably. If it fouls in just a few hours you need to do something. A BY plug may increase your cleaning interval, but doesn't solve anything. How's oil consumption? Does it go black quick? Do you get belly oil? Jugs come off an RV pretty easy because there's almost nothing in the way.
 
Might try some UREM37BY spark plugs (formerly Unison, now Tempest) in the lower holes. They resist fouling a little bit better, and often can still fire even when loaded up with gunk. I run them in the bottom holes of my RV-6 and used to run the entire set of them in my old Cherokee.
 
Guys,

Thanks for the great info. I will consider trying different plugs on the bottom. I was unaware that certain plugs resist fouling better than others.

So far the oil consumption is fine. About a quart in 25-30 hours. I run 5 quarts because any more than that and it comes out on the belly during light acro.

I will be monitoring this more closely however. I had the compression checked yesterday and all cylinders were 75-77.

I also had a boroscope check done. Again all looks good. No scoring or grooves.

There was more Chromium and Iron in the last oil analysis so there is something going on I'm afraid but it's not clear yet.

All indications are to keep flying and monitor. I will get another oil analysis done in 25 hours, rotate the bottom plugs more frequently and only take drastic action when I'm convinced it's needed.

Sound like a plan?

Darren
 
My situation may be completely different but I had similar symptoms. Then I noticed increased oil consumption. When it got to three quarts in 1.5 hours I was on a trip and grounded the plane.

Checked compression on cylinder #4 and it was in the low 50s. The oil ring was broken.

I think that I have Superior cylinders and the excessive choke may have been a factor (opinion).
 
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?
 
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
 
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
 
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:
Good info thanks for sharing Darren.


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

.... no excessive oil burn (burns about a gallon in 30 hours).
Click to expand...
 
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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