Metal debris in oil/grey oil of M20B25

[14thirty]

Drained the oil out of my M20B25, found metal debris on the plug magnet. The oil is dark grey. It was running fine. Has been turboed for about 5 years, but not done many miles. Don't know the mileage or previous use of the engine. The block is untouched by me. Previous oil changes have always had clean looking oil.

Am I right in saying there's no point taking the sump off to have a look (given it's awkward with the engine in place), and it's going to require a full strip down? What is likely to have failed?

[82eye]

i'm guessing rings. top is probably good. looks like a bottom rebuild at any rate. it won't matter if it's only rings, it all gets done when opening the bottom.

[TobyB]

Oh, yuk.

Time for more looking before disassembly, but agreed, that doesn't look good.

Give those chunks a brake clean bath and shoot some closeups.
That might help narrow it down...

Me, I'd pull the valve cover to look at the cam and rockers,
and also stuff a borescope down the plug holes,
just to see if I could see more. The side- facing borescopes tell all...

If you don't see anything, then leakdown and compression

t
has had pistons come apart...

[14thirty]

Not had a chance to look any further, got some close up of the debris though. There may have been some knock last time I had it out, don't have detection though just my ears.

[TobyB]

Those are some odd chunks- off the top of my head, they don't look familiar.
Like, parts of a small spring and...
Kind of like something with a small ball bearing is coming apart?
You don't have a ball- bearing turbo, do you?

hmmm....

t

[14thirty]

Everything under valve cover looks fine. Pistons look OK with borescope, though it can only see straight ahead so can't see that much. Mirror attachment is too big to fit.

Turbo is journal bearing.

I don't think there's anything to be gained by looking further, it's going to need engine out and stripped to fix whatever it is.

[E30SPDFRK]

Those looks like little bits of RTV mostly, except for the silver sliver. You're sure it's all metal?

[14thirty]

Definitely all metal, and it's magnetic.

[14thirty]

Finally got round to looking at this, ringlands on #5 + #6 are broken. #6 is the worst. #4 Has broken the top ring. All the skirts are pretty badly scuffed. There is some damage/wear to the bores. Main and rod bearings are worn.

Not sure if this was caused by knock or/and rings not having enough gap. It's the early euro engine with 9.7:1 pistons. Was running about 16psi looking at the last log.

[McGyver]

Those are fucked. But replacement double over (+0.50mm) pistons are available and cheap! That should be enough to clean up the bores and put it back together in a stock configuration.