Strange stuff.

[flyguy]

One lower plug went sour on my -85 and when I pulled them to check I found this little metal ball about the size of small birdshot wedged between the top of the center insulator and the inside wall. Wasn't what was killing the plug, but it is rather curious. It is black and hard, not like lead deposit, somewhat porus, a lot like the balls that form from welding splatter. Not magnetic.

I have used some automotive anti-seize that I think is aluminium paste, but I used it pretty sparringly.

Anyone see anything like this before?

DC

[d.grimm]

Re: Strange stuff.

Sounds like lead to me. Look at the plugs on a Lycoming 0-235-L2C (C-152)
sometime. I've had good luck with TCP in the gas.
Dave
P.S. Are you sure that wasn't your plug problem? It usually grounds them out.

[Guest]

Re: Strange stuff.

Do you use auto fuel or avgas?

Ditto on the lead comment above.

Dave (the other Dave)

[Doc]

Re: Strange stuff.

Agree with lead fouling...I used to have that problem on my Lyc O-360 with my Mooney M20C...cleared with TCP and leaning. Clean, gap, and test... or replace. I assume you have looked at the other 7 plugs. Doc

[flyguy]

Re: Strange stuff.

Big negative on the lead guys, as I said before. Yes, there are lead oxide deposits in the engine, and I clean them out of the plugs regular. BUT they are pinkish and look like cat litter. They are also somewhat soft and brittle. This thing is HARD, and a bit shiny when you scratch it.

My best guess it is aluminium, if so I hope it is from the anti-seize that I used, and not from the piston (yikes.) I can see no damage to the piston surface and was ok when we used borescope before.

The center electrode was being shorted by a sliver of other non-descript material that was stuck in the gap. Dark like carbon maybe.

The bottom plugs get cleaned pretty regular and there were lead deposits down in the bottom of one other bottom plug, but they looked like, well, lead deposits, you know.

DC

[VictorBravo]

Re: Strange stuff.

I will guess it's metal from something in the engine, that got sucked into the combustion chamber, liquefied in the heat, and deposited in the plug during the compression stroke. Think of all the aluminum upstream of your combustion chamber and downstream of the air filter...

Carburetor body
Intake spider burrs, shavings,etc.
Intake elbow at cylinder burrs, shavings, etc.

Now think of all the aluminum in the upper cylinder:

Cylinder head / combustion chamber
Piston lands

I'd be going in there real soon with a borescpoe, looking at the tops of the pistons at the outer edges, to see if you chipped off a piece of a piston land/groove. THAT would eventually crack and shatter a piston in flight, guaranteed to be 500 feet over a forest or a swamp.

Bill

[d.grimm]

Re: Strange stuff.

I was flying a C-152 that broke a piston and it just seemed like a leaded up plug. Pulled the plug and it was PACKED FULL of aluminum. Might try a compression check while you are at it. Good luck, these usually are not happy outcomes.
Dave

[flyguy]

Re: Strange stuff.

Bill, Dave, That is what I have been thinking about. Some oil has been showing up on that bottom plug and I just checked the log and #2 is the same one that was down on compression. Was coming back thru the intake a bit so we thought it was the valve sticking. Probably more than that.

Think you guys are right. Borescope and/or time to pull cylinder, yuk. Engine still running strong, but that is too many signs, I'm not taking any more chances.

Thanks,
Darryl

[VictorBravo]

Re: Strange stuff.

Use of Borescope on loan from some FBO at the airport... $5.00 and a six-pack

Bandages and First-Aid spray for skinned knuckles on edges of engine while removing cylinder... $3.29

NOT having a forced landing that requires two days of hard work to retrieve the wreckage, six months of aircraft restoration, and $7,500 in materials... PRICELESS !

[gfortin]

Re: Strange stuff.

I would check that out with a borescope very carefully. I blew a hole in piston in a 0200 taking off from Plymouth MA. I was only 100' and I was lucky to be able to maintain 1300 rpms and was able to land back on the runway. If you have that experience, it will pucker your sphincter. Good luck I hope you find the source.

[flyguy]

Re: Strange stuff.

Bill, that is almost too scary to be funny. And on the off-field, been there, done that, not fun either.

I think that cylinder is coming off. Likely will not even bore-scope it. Looked in there with LED light today. Too much oil getting in. Something isn't right.

Thanks all,
Darryl

[crispy critter]

Re: Strange stuff.

Bill, that is almost too scary to be funny. And on the off-field, been there, done that, not fun either.

I think that cylinder is coming off. Likely will not even bore-scope it. Looked in there with LED light today. Too much oil getting in. Something isn't right.

Thanks all,
Darryl

Better safe then sorry.