Making a Little Bit of Metal

MartinPred · #1 03-01-2016, 09:41 PM

So over the past two years, the iron in my oil samples has been slowly creeping up. But the filter was always clean so I just kept an eye on it.

On my last oil change however, I was able to tease a little bit of ferrous particles out of the filter with a magnet.

The engine is a Lycoming O-360-A1D with Bendix mags, about 600 hours since factory re-man.

Here's the oil data:

Filter at first glance looks pretty clean:

But with a magnet, I'm able to pull out tiny ferrous particles:

The engine has been running great. And I watch my CHTs like a hawk. Here's a recent flight:

Blackstone still thinks it's not urgent, and recommends checking back in 30 hours. But I did find something that was worrisome--a possible crack in the engine mount:

Hard to tell if the crack goes through the paint or not. But the fact that it runs along the tube has me worried. Could vibration also cause some wear inside the engine?

At this point, I'm inclined to take Blackstone's advice. But I'd love to hear the thoughts of the engine guys out there.

-Matt
N402BD

airguy · #2 03-01-2016, 10:03 PM

Could be the picture, but that looks more like a rub mark from something than a crack on the engine mount. In any case, a crack is much more likely to occur at a weld, and be circumferential, than lengthwise.

A problem with the engine mount also will not be connected to a rise in ferrous metals in the oil analysis. You are chasing two different problems, unrelated, and one of which may not be a problem at all.

MartinPred · #3 03-01-2016, 10:13 PM

Greg,

In the picture, the cracks on the mount are the things that look like scratches. Very fine, but definitely cracks in the paint. Just not sure if the tube underneath is also cracked. Seems like a strange place for that to happen. I'll keep an eye on it.

As for the metal, Blackstone suggested that it might just be "the new normal" for my engine. And I'd hate to start tearing it apart if that's the case.

I'll probably fly another 20 hours or so, change the oil, and see how it looks.

-Matt
N402BD

Michael Burbidge · #4 03-01-2016, 10:21 PM

Mike Busch wrote a very good article about how much metal is too much. That sort of thing. Look it up in the EAA archives.

MartinPred · #5 03-01-2016, 10:47 PM

Of course. A quick google search reveals that Mike Busch has written a couple of articles on the subject. And Lycoming has issued some guidance in the form of Service Instruction 1492C.

Turns out in my case, since Aluminum is not elevated and the particles in the filter are few in number and smaller that 1/16", Both Mike and Lycoming recommend putting the plane back in service and checking again at the next regular oil change. So that's what I'll do.

Thanks guys!

-Matt

BillL · #6 03-02-2016, 06:00 AM

Your profile does not say where you are - like humidity and temperature environment. Looking at the time between changes, it appears the plane can sit a while. Depending how you fly - short vs long times, and how long the oil is hot, and if you use heaters it could be some mild corrosion due to internal moisture.

Silicon is not elevated, so it is not getting dusted.

If that is the case then changing your routine may help drop the iron. May not, but worth a try.

Do you have an oil separator or a straight exit breather?, is there any water related whiteness/condensate on the dipstick?

All these thing might give some clues, or it is a piston pin scraping the cylinder wall, or a slowly eroding cam/lifter unrelated to operation and nothing to do but open ad repair. In any case, more investigation is in order to prevent proper discovery of the root cause later on. No use in getting oil samples if no action is taken on the results. It may, indeed, be a fundamental issue unrelated to anything but chance.

PRL - what kind of barrels, and rings? Probably not ring de-lamination as oil consumption would be rising, so scratch that.

I really don't like iron in the filter after the initial oil changes cleans everything out. Good luck.

MartinPred · #7 03-02-2016, 09:18 AM

Bill,

The airplane did spend some time as the hangar queen while I was overseas in 2012 and again in 2014. Plus I missed a sample on an oil change in 2014. When the plane was sitting (maybe two months tops), it was in New Mexico. So I'm hoping corrosion is not the issue. But I have been in South Dakota the last two years where there is a touch of humidity in the summer.

I'm pretty sure the A1D has steel cylinders, so the most common culprit for that is the piston plug (hence the Lycoming SB). I may be pulling some jugs in the future.

-Matt

MartinPred · #8 03-02-2016, 09:20 AM

Also, straight breather tube. Normally I don't see any moisture in the little bit of oil that drips out while the plane is sitting in the hangar. But after the last cold snap, I did see some.

-Matt

BillL · #9 03-02-2016, 09:36 AM

It sounds like it is not corrosion, so it is something else. Yes, SD should be pretty low in all around humidity, and there were no spikes in iron, so less chance of corroded cylinder walls. Jug inspection through spark plug hole seems in order, but inspect the particles magnified, or send a collection of particles to Blackstone for metallurgical analysis. That would help identify the source.

Lifters could be another consideration, but an analysis should help narrow that down. Sorry, we could not be more help.

PerfTech · #10 03-02-2016, 10:29 AM

....You may want to consider one of these. It will catch all the ferrous materials, prior to them going through and damaging the oil pump. It will also catch all the particles too small to be caught in the filter. When removed it will give you a 100% visual of all this type of material that has been generated in your engine, making comparisons from one oil change to the next very easy.
Thanks, Allan..

http://antisplataero.com/Magnetic_Super_Plug.html