[NovatoriusRex]

I performed my first open-oilfilter surgery tonight after considering the motor broken in. Is there anything tell-tale I should be looking for in the filter media? More importantly, what SHOULDN'T I be seeing in the media?

 

[David_D.]

If it's a freshly rebuilt motor, you should expect to see a dull grey material that is metallic (cylinder wall and normal). You may also see very very little amounts of shiney flaky material. If there is an abundance of shiney flaky material (a lot), more often than not it is premature cam/lifter wear (unless you are running a roller). Depending on the assembly lube used, the oil may appear a little milky or hazey.

 

[Paul Wright]

Aircraft owners often check the oil filter for early warnings signs of engine trouble. Aircraft engines are expensive and engine problems way up in the air aren't good.

Analysis of Engine Contaminants
Imagine you have just purchased that dream airplane. During the purchase, you did everything right. You had the airplane checked out, including a pre-purchase inspection. The engine was examined and an oil analysis sample was taken with normal engine wear reported by the lab. The airplane is in perfect condition.

Six months later, your shop tells you that the engine is contaminated with metal, the camshaft is shot, and the engine has to be disassembled. The cost of repair is no less than $3,000 and probably more.

Unfortunately, once or twice a year, I see one of these engines. What is more unfortunate in some cases is that the engine had already failed before the purchase; the normal pre-purchase inspections had failed to detect the failure.

An engine can operate normally, pass compression tests and oil analysis, and still have damage to the camshaft lobe and follower. Even when a camshaft lobe has ground down to 1/2 its original shape, the only indication is that the engine fails to produce rated power. Engines with a fixed-pitch propeller may not produce rated RPM. But on engines with a constant-speed propeller, lack of engine power may not be noticeable. Engine roughness occurs only when the camshaft lobe has been totally wiped out.

There is one specific type of inspection that detects this type of occurrence in the early stage without disassembling the engine: a thorough oil filter examination.

Proper inspection of the oil filter is the best method of detecting camshaft or cam follower spalling and failure. Cut the oil filter open and wash and rinse the filter media carefully into a bucket of clean solvent. The washing shifts particles into the bucket. Using a clean magnet, work it around in the solvent solution. Ferrous metal particles in the solution will adhere to the magnet, allowing inspection. A visual inspection of the cam followers is warranted if the end of the magnet is covered with metal slivers.

You will not detect early signs of cam follower damage by taking the filter media out of the can and spreading it out on a table. There is not enough metal at this stage of failure to be visible in the folds of the filter. Oil pressure forces the small slivers of metal into the filter media where they are not visible. A magnet concentrates the small amount of metal, making it visible. Unless the examination of the oil filter is done correctly, you will not get a reliable analysis.

Examples of aircraft filter inspection saving the day and money
(Aussy Flight safety newsletter Download PDF)

Here's some pixs:
aircraft oil filter inspection

It works for cars too!
A good streetrod article on how to check oil filters for contamination including magnetic, non magnetic, gas, water or antifreeze.

Goodson FIT-1 oil filter cutter instructions (PDF) Transfering small particles onto a microsope slide for viewing is a good idea.

Tavia oil filter cutter and filter stand (you could make this from a U-bolt and angle iron)

A billet tool:
Steve Schmidt filter cutter (not an endorsement)

 

[Maxturbo]

More importantly, what SHOULDN'T I be seeing in the media?

A simple magnet test will separate the ferrous from non-ferrous material. Ferrous (iron) particulate will originate from casting flash, machining efforts, cylinder wall / ring and camshaft lobe wear (to mention the common sources). Most everything else is bearing, stock cam sprocket and piston related non-ferrous debris. Neither one is good, but very small quantities are acceptable during break in. Magnet testing can help in narrowing down your concerns or subsequent search.

 

[NovatoriusRex]

This pic ISN'T of my filter material, but I did see a FEW pieces that looked like this in the filter & hanging from the magnetic drain plug that looked very similar to this.

I would think that some of this would be expected since no one's machining abilities are perfect. I saw maybe half a dozen such pieces of metal in total and not much of anything else.

Should I be concerned?

 

[Maxturbo]

Appears to be steel machining chips (line bore or even head work possibly). Needs the magnet test to help confirm origin. Lesser chance that those are non-ferrous in nature. Either way, poor flush and clean on somebody's part. Should you be concerned? Yeah. To what degree? Depends on the amount and if still apparent in follow on oil changes. Enough to open and inspect the engine? Tough call.

 

[NovatoriusRex]

Thanks Max. After I posted my messages, I thought about it more and the stuff did look a whole lot like someone's lack of cleanup. Hopefully none of it made it to the bearings.

I'll have to give it some more running time and then keep checking the filters for further evidence of stuff.

 

[Baddbob]

Just a tip on reading filter cuts: I good friend of mine showed me this trick years ago after he was professionally trained on filter inspections. Cut the shell off the filter, use a knife to cut the filter media off, cut the media in two and wrap each in a rag then squish the oil out in a vise, the rag will soak in the oil. Once the oil is squished out you will not believe the difference in detail that can be seen on the debris-at least 2X more can be seen.

 

[Baddbob]

Just a tip on reading filter cuts: I good friend of mine showed me this trick years ago after he was professionally trained on filter inspections. Cut the shell off the filter, use a knife to cut the filter media off, cut the media in two and wrap each in a rag then squish the oil out in a vise, the rag will soak in the oil. Once the oil is squished out you will not believe the difference in detail that can be seen on the debris-at least 2X more can be seen.