The International Cessna^® 170 Association

Had kinda a bad day today I guess. I turn 40 tomorrow so I decided to change oil today in preparation to celebrate with a day of flying. Took a short flight to warm up oil. Next dropped oil. Screen loaded with non-ferrous flakes which we identified as cylinder chrome. Probably about 1/2 a tablespoon full with just a slight dusting of ferrous material picked up by a magnet which my ame says is next to nil. Now my question 170hrs since major with overhauled cylinders about 7 years ago 2 of them chromed.About 80 of those hours in last 2 years. Is it feasible to replace chromed cylinders and go,I have 2 spare overhauled steel cylinders, or do I need to tear down because of fine material getting by the screen and possibly ending up embedded in main bearings, chewing up the crank?
Thanks in advance for your good advice.
Kim

What makes you think all the non ferrous metal in your screen is from your cylinder wall?

In addition to the main bearings, a couple of places that get really gummed up with metal flakes once they start circulating through the engine are the lifters, push rods, and the rocker arms. They have really small orifices that don't allow for easy ejection of foreign material.

Going to look deeper into this thing today but flakes are really thin hard and brittle which my ame said seemed like cylinder chrome. would large pieces be hitting lifters etc.. or would their oil supply not be screened?

The unfortunate thing about screens is they don't filter. They "sift". I urge everyone to modify to a spin-on filter.

As for your situation, Aryana is giving good advice, IMO. Boroscope those cylinders to see if you don't have a broken ring or such damaging one of the chromed ones. If you find so, then pull that cylinder and look into the engine to make a subjective judgement as to whether or not to flush and fly.
(Make the repair and with fresh oil fly it for a short period, then change the oil again and sample the screen/filter. If the deposits have largely gone away, continue with another oil change in the near future for monitoring purposes, etc.)

This is not going to be something scientific. It's going to require some subjective judgment on your and your mechanic's part.

If indeed it's chrome and you want to play it safe, I would stop running the engine. As your AME can repair your engine, I would tear it down and hope your crank has survived. My reasoning here is the bearings are relatively cheap, the bigger parts are hard to find and expensive.

Yes. I regret that I did not add that as the safest route.

My ame talked to one of the engine shops here in BC and they basically said not likely chrome unless run low on oil (which I haven't) causing high temps and subsequently detonation. They strongly suggested wrist pin plugs and said heat in cylinders would make material brittle. My mechanics gone till next week so I guess we'll dig into it when he gets back till we find cause and decide from there. The joys I guess
Kim

as expensive and hard to find as cranks are. I'd pull it and be certain there is no debris doing damage to the crank.

My experience is this; Any part of the engine that is exposed to oil under pressure or scavenge or just flying around down stream of the offending metal maker can (Absorb) or capture some of that metal especially when only a oil screen is in the system. Examples could be cam, rod or crankshaft bearings, piston skirts, wrist pin plugs. Now the next issue is what type of metal is it? If it's ferrous well big trouble if you continue to operate the engine, Non ferrous not as much but it certainly will cause the same, to generate heat when trapped between moving parts. The heat build up alone can ruin any part and you have all mentioned those really expensive ones. The excessive wear is also out there to consider. My take is as yours, tear it down and investigate before any more harm is done.

I hope it turns out to be somewhat minor

Just my thoughts

There is no chrome in a 0-300 other than the chrome cylinders. wrist pin plugs are aluminum.

That was my thought too, Tom.

Take a flake or two and put in on an anvil and smack it with a hammer. If it flattens and spreads...it's likely aluminum.

gahorn wrote:That was my thought too, Tom.

Take a flake or two and put in on an anvil and smack it with a hammer. If it flattens and spreads...it's likely aluminum.

What he has is an old chrome cylinder that has corroded under the chrome, and it is shedding metal flakes.
And with no filter those flakes are ruining the oil pump, and crank, and most likely the hydraulic units are full of it,and cam is being ground away by them.

Bu what do I know? I've only dealt with 40-50 ruined engines due to old chrome cylinders doing this.

gahorn wrote: Take a flake or two and put in on an anvil and smack it with a hammer.

Who the he-- would have an anvil anymore? Who can see well enough to hit speck of metal?

All my shop vises have anvils on them.

Ok now for a new twist.
Pulled plugs and boroscoped cylinders. Nothing noteworthy showed up. Did cold compression test. All 64-78. Pulled engine to send off for tear down. First sign of trouble thru starter hole. Right mag was working before my last 20 min flight to warm up oil. But obviously isn't now. Here's the groove chewed in accessory case where gear was rattling around for up to 20 min. So somewhere inside we have broken cam gear retainer pieces. Planning to get it tore down for further analysis. Hopefully find more out next week. My ame tried to talk me into putting a low time IO360 out of a crashed chopper in but I don't think I have that much cash!

integritywood wrote:Had kinda a bad day today I guess. I turn 40 tomorrow so I decided to change oil today in preparation to celebrate with a day of flying. Took a short flight to warm up oil. Next dropped oil. Screen loaded with non-ferrous flakes which we identified as cylinder chrome. Probably about 1/2 a tablespoon full with just a slight dusting of ferrous material picked up by a magnet which my ame says is next to nil. Now my question 170hrs since major with overhauled cylinders about 7 years ago 2 of them chromed.About 80 of those hours in last 2 years. ...

integritywood wrote:Ok now for a new twist. ...Right mag was working before my last 20 min flight to warm up oil. But obviously isn't now.
...So somewhere inside we have broken cam gear retainer pieces. ...!

So, when you made that "short flight to warm up oil"... what do you think you might have missed on your pre-takeoff run-up? (or useful item we could add to our post-flights?)

I also wonder if you know the source/pedigree of that mag gear? (I'm wondering if it isn't from an old prop-strike which wasn't properly addressed.)