Bronze flakes in oil after cylinder replacement

[PatThomas]

Hello 170 members - I've read this very informative forum for years but have never posted. I'm hoping for some advice on the following:

'52 170B with mid-time C145. Recently at annual one cylinder was replaced with a new Superior cylinder. After 10 hours break-in per Superior's recommendations, oil was changed and there was a fair amount of fine bronze colored flakes (non-ferrous) in the oil filter (Stratus spin-on oil filter installed). After new oil and filter and 10 more hours of flying another oil change found the same or slightly more bronze flakes in the oil filter. My mechanic inspected the rocker arm bushings on the new cylinder which looked ok and then inspected the rocker arms on the other 5 cylinders which looked ok. Engine is running fine with good compressions and was not making metal before the cylinder replacement.

My questions are:

Is bronze in the oil common after a new cylinder? If so how much could be considered normal and for how many hours after cylinder replacement?

Other than the rocker arm bushings, what else in the engine would be producing the bronze flakes?

Thanks in advance for any help.

[cessna170bdriver]

My guess would be valve guides, though I’d be surprised for there to be enough to be visible. When the cylinder was replaced, did you re-torque both sides of the through-bolts? If not, or if the crankshaft was turned while the cylinder was off, it could be a spun bearing. (Bronze is metallic, and a copper or brass color, but non-ferrous).

[c170b53]

Based on the continuing metal production, I would say Miles has given you the bad news. Pull the cylinder to ensure nothing stupid is going on but sounds like you’ll be going much deeper. What’s mid time? and years in service since O/H?

[PatThomas]

Thanks for the replies. Miles, you are correct I should have said non-ferrous metal. Opening up the oil filter there was non-magnetic bronze colored fine flakes throughout most of the folds of the filter. Definitely a significant amount of visible sized particles that are coming from somewhere. No other metal observed. I'll be talking to my mechanic this week, but at least now I know the direction we're headed. Sounds like the new cylinder needs to come back off for inspection, and from there it gets serious.

[4583C]

Pat
When I started running my freshly overhauled engine with six new superior cylinders we changed the oil at slightly over 2 hours chasing an oil pressure problem and it was producing a scary amount of shiny bronze flakes. Consulted three different engine builders who all said to run a little more before condemning the engine. Got a new oil pressure relief spring and flew it another three hours and changed oil and filter and the flakes got even smaller in size and volume. With the pressure problem cured we brought it back to Tx and changed again at 12 hours and the gold mine had nearly petered out. Now I had six new cylinders rather than one but who can say whether the problem was from one cylinder or all of them. By thirty hours it was hard to find a brass flake in the filter. I’ll pm you my email and will send you the pictorial evidence if you like.

[c170b53]

I guess a picture here would be beneficial.

[hilltop170]

These are pictures of what came out of the oil filter after the first 3 oil changes after overhaul with new Superior cylinders on Paul’s 170.

Click on pictures to enlarge

1st oil change 2 hours after o/h w/new Superior cylinders

2nd oil change 5 hours after o/h w/new Superior cylinders

3rd oil change 12 hours after o/h w/new Superior cylinders

[c170b53]

Thanks Paul. Looks like essentially powder, its also a bit hard to see the amount in the picture (maybe that’s me). At work we use white paper filters, almost like coffee filters lay them flat after collecting the material and use a magnet underneath to see whats magnetic, what’s carbon and so on.
The single cylinder replacement description / interpretation of metal found and the possible subjective assessment of an increase in metal between samples could also mean nothing is wrong. So I would say I was possibly premature / wrong to say something isn’t right unless of course the metal is increasing and does not begin to diminish.

[GAHorn]

Thanks Paul. Looks like essentially powder, its also a bit hard to see the amount in the picture (maybe that’s me). At work we use white paper filters, almost like coffee filters lay them flat after collecting the material and use a magnet underneath to see whats magnetic, what’s carbon and so on.
The single cylinder replacement description / interpretation of metal found and the possible subjective assessment of an increase in metal between samples could also mean nothing is wrong. So I would say I was possibly premature / wrong to say something isn’t right unless of course the metal is increasing and does not begin to diminish.

So.... How does the coffee taste at your work..?? (Increasingly bitter..?? Or metallic...??)

Sometimes when a bushing (such as a rocker-arm-pin bushing) or valve-guide is reamed during mfr... the assembly is insufficiently cleaned afterward... or sometimes if reamed in the field... metal will show up in the filter... but it should not be INcreaseing... it should decrease, of course. Either way, it’s sloppy workmanship tho’.

[daedaluscan]

Starter bushing? Pretty easy to check.