Normal or not??

Darren S · #1 10-03-2012, 06:57 AM

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

aerhed · #2 10-03-2012, 08:16 AM

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.

Darren S · #3 10-03-2012, 08:44 AM

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

DanBaier · #4 10-03-2012, 09:14 AM

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

SMO · #5 10-03-2012, 09:21 AM

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.

erich weaver · #6 10-03-2012, 09:54 AM

Quote:

Originally Posted by DanBaier

First thing I'd do is to check the resistance of the plug.

Yup. Champion plugs are notorius for internal failures resulting in high resistance. Check out the Mike Busch/EAA webinar on spark plugs.

erich

aerhed · #7 10-03-2012, 12:26 PM

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.

Neal@F14 · #8 10-03-2012, 01:41 PM

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.

Darren S · #9 10-03-2012, 04:19 PM

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

Ron Lee · #10 10-03-2012, 04:46 PM

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).