Engine problem

[Rich]

Well, during annual this year iron was detected in my oil filter. In Lycomings this usually means valve tappet/cam lobe spalling and wear. Sure enough, with about 1150/1450 hours I had to have the engine popped open and it's in for repair now.

Damage to 3 tappets and 2 cam lobes, plus some collateral damage to a couple of other things.

Some pictures:

[rwtucker]

Rich,

Bad news! Do you think the high relative humidity in your area played any part?

[Rich]

Rich,

Bad news! Do you think the high relative humidity in your area played any part?

That'd be a guess, when coupled with occasional periods of inactivity (though not a factor this last year, particularly). This is known to be a problem with Lycomings, as the camshaft sits high inside the engine and the tappets and cams are the first components to have lubrication leave the interfacing surfaces. There's also a suspicion lurking out there that inadvertent high-RPM cold startups could contribute to this problem. Since I have not been the sole user of my plane, I can't say that hasn't happened.

There's another possible factor at work here. I'm reluctant to start a pointless discussion on lubricants, but for 11 years I used Shell 15W-50. Then 2 years ago I switched to the Phillips X-C. No particular reason. But I forgot that the Shell has the LW 16702 additive included in its formulation, which the Phillips does not. This additive was first developed by Lycoming in the '70's to combat - you guessed it - tappet/cam wear. Especially in certain engine variants of theirs. Correlation meaning causation? Maybe. Anyway, I'll be going back to the Aeroshell.

Here's food for thought: The camshaft has only 6 lobes. There's a separate one for every exhaust valve, but the 4 intake valves are served by 2 lobes (Cylinders 1-2 share a lobe, as do 3-4). An intake lobe and an adjoining exhaust lobe are the ones damaged.

FWIW, I estimate that each of the 2 intake lobes in my engine has performed about 190 million valve cycles, while each of the exhaust lobes would be half (~85 million) that number.

[rwtucker]

Interesting thoughts. I worry about the moisture not because of high RH but because I flew so many hours with 170 degree oil before I taped my oil cooler.

The real facts on oil are a mystery to me. For no particular reason either, I switched to Exxon Elite from Shell 15W-50 and I'm adding about 1/3 bottle of CamGuard to each change (about 5 qts.). I can't prove it but the Exon "seems" to leave more of a residue after several days. I say this only from playing around dipping a screwdriver into the oil bottle and letting it drip off. There is probably an experiment in there someplace but I did not control for temperature, etc.

Not necessarily related but my Turbo Dakota spent much of its life in Houston with nothing but Shell with no additives. The earlier engine (before the F-REMAN) had corrosion problems and its oil runs hot enough. I'm still running Shell in it but I haven't seen the cam. I'm not sure I want to.

I've only had one high RPM cold start but the cause was a stupid owner/pilot trick Hopefully that was not enough to break the cam surface.

[Rich]

I do have chronic low oil temperature problems (rarely reaches 170), and that could be a piece of it, also. But it's been this way since day 1. Since the plane is going to be moved to a dryer and warmer-summer climate as soon as I get it back, I'll be revisiting the oil temperature issue also.

[Steve]

Rich:

Sorry to hear about your engine troubles. Have you been performing oil analysis? If so, did it show anything prior to the oil filter metal appeared? I have done oil analysis at each oil change for the past 14 years, and my numbers have always been very good, but I wonder a lot about my cam lobes and lifters, since I have had periods of inactivity. I've used Exxon Elite since break in.

Steve

[Chris B]

Hi Rich -

I am sorry to hear about your engine issues. Those are some expensive photos.

The shot with an apparently pristine lifter directly adjacent to a badly spalled lifter is shocking. But it would seem to add credence to the theory that once corrosion gets started it tends to progress inexorably.

What was the longest gap in activity? Also, any color on the iron quantity in the filter? IOW, was it subtle or pretty obvious?

Chris

[Rich]

The longest period of inactivity would have been the fall of 2009, when the plane sat, parked for 100 days due to the saga of my MT prop. It was hangared at the time, though unheated and it got damp in that hangar when it got damp outside.

But every once in awhile various circumstances (weather, scheduling conflicts, etc.) would have it sit a month or so. It's been tied down outside for about 4-1/2 years now.

I had oil analysis done from time to time. The last was a year ago. Always showed within norms. This all happened within about 40 hours of tach time.

The metal flakes in the filter were shiny and clearly visible, once the oil was squeezed out of the filter element. Passing a magnet showed they were all iron-based.

Because of the engine design you really can't examine the surfaces of the tappets or cam lobes without pulling cylinders. The damage was fairly confined, but a few flakes of the stuff got into one of the cylinders and scuffed up the surface and the piston. And scuffed up one of the valve seats. It's worth noting that the damaged cylinder didn't show any compression-check problems - this time around. But using a "poor-man's-borescope" did show the cylinder-wall damage.

[Lance Murray]

Rich, I had this same repair on my 2002 and my 2007. Both were being flown regularly in a flight school. One in California where it is dry and the other was in florida. This was a Lycoming issue. The 2007 was repaired under warranty at around the same hourly time. When the 2007 was repaired they changed it to roller tappet at no additional charge. I believe they had a problem with metallurgy that they never owned up to and the roller tappet was lycoming's attempt at fixing this.

[rwtucker]

I believe they had a problem with metallurgy that they never owned up to and the roller tappet was Lycoming's attempt at fixing this.

Bad news! Any idea what serial number marked the transition or did it work that way?