o-300 D making metal - but where?

[Kyle Wolfe]

Looking for your thoughts...

Some history:
Engine TT 2641
TSMOH 952

About 5 hours ago oil consumption quickly jumped (went from 1 qt. every 6-8 hours to one quart per hour).

Oil pressure has remained strong and steady.

Oil temp has remained steady.

No oil on belly. No oil leaks.

Sudden high oil usage bothered me.

Pulled the plugs and no visible difference.

Towed the plane over to my IA.

Did a compression check and with no finding of any weak cylinder(s).

Dropped the oil and found metal in the screen as well as in the case. Metal was aluminum.

Exhaust stack visual analysis appears to indicate oil burn on engine's pilot side (cyls 2-4-6).

Bore scope analysis done by my IA turned up nothing.

#6 cyl dome appears to be whiter than others.

Will begin pulling cylinders starting with #6.

I've done quite a bit of searching on our site and haven't found a lot other than possible piston pin plug issues.

We're a bit baffled at this point:
Why is compression still good?
Why didn't visual bore scope turn up something?
Are we missing something else to look at before pulling cylinders?

[bagarre]

What kind of metal? Aluminum, bronze, steel?

[Kyle Wolfe]

Aluminum.

[bagarre]

Re-read and somehow missed that you said it was aluminum.
Yeah, only thing that comes to mind is piston pin plugs. Others will know more tho.

[cessna170bdriver]

I second piston pin plug(s). I've had it happen, and when the offending cylinder was pulled, what came out of one side of the piston pin was a polished oblong chunk of aluminum that looked nothing like a piston pin plug.

[hilltop170]

Bummer, Kyle-
What I have seen with piston pin plug wear is that the chips look like finger nail clippings, small, thin crescent shaped chips.

If that is what is happening, and you will know when the offending cylinder/s come off, is how to purge the rest of the engine of remaining debris. I'm sure others have done this before but I have never heard anyone discuss it. Is a teardown required or can the engine be effectively flushed clean?

[blueldr]

You are getting metal? Is it flakes or is it nuggets? Flakes are not at all good, but nuggets are really bad! It's just the opposite of gold panning.

[Kyle Wolfe]

No screen collapse.

Am getting flakes - no nuggets!

After pulling the 6th cylinder we found the culprit. Pin plug as expected. Now time to decide what makes sense when having all 6 cylinders off.

Looks like some flakes stuck to the oil ring thereby causing the oil use. Nothing on compression rings which led to the good compression.

[blueldr]

Decarbonize it, deglaze the cylinders with a dingleberry hone, lap the valves, ring it, and put it back toghether with new wrist pin plugs as needed.

Might be a good idea to flush the galleys and change the oil too!

[bagarre]

Decarbonize it, deglaze the cylinders with a dingleberry hone, lap the valves, ring it, and put it back toghether with new wrist pin plugs as needed.

Might be a good idea to flush the galleys and change the oil too!

^ +1

[daedaluscan]

Decarbonize it, deglaze the cylinders with a dingleberry hone, lap the valves, ring it, and put it back toghether with new wrist pin plugs as needed.

Might be a good idea to flush the galleys and change the oil too!

I wonder if there will be anyone to say this kind of thing in 20 years? Simple, practical solution, for a simple practical engine. These things really were designed to be fixed, not replaced.

[ghostflyer]

After popping on the affected cylinder and checking the filters and before changing the oil , I would be undoing the engine mounts and lifting the engine up and pulling the sump off for a clean and inspection . You would be surprised to find what sits in the sump . I would be changing the oil again at 15 hours later also .

[GAHorn]

Five hours an a screen-sample would be a good idea.
Most things sitting in the bottom of sumps remain in the bottom of sumps. I wouldn't pull it unless subsequent samples cont'd to repeatedly show contaminants....after-all...THAT is what the screen is FOR, to collect the stuff out of the sump.

[MoonlightVFR]

I second the suggestion of not pulling the Oil Pan too soon.

a number of things could wrong.

Dr do no harm

[Kyle Wolfe]

The engine shop miked out the cyls and one other one was at max limit so decided to order 6 new Superior cyls. Decided it was the more prudent thing versus having them all inspected and gone through. Figured I had them all off so now is the time.

Also ordered a F&M filter adapter. Will flush the engine well before putting on the new cyls.

Will install new motor mount bushings too as long as the engine is light. Those were on my next annual list anyways.