Large Metal Chunks in Oil Filter

Hi everyone,

I’d like to get some thoughts on what I found in my oil filter today. For context, its a 2008 M3 6MT with 187k kms, new to me and first M car I’ve owned, although I’ve owned many other BMWs before. Previous owner claims he had rod bearings measured and his mechanic told him they were in excellent shape and didn’t require replacing, but no proof other than a photo of the measurement values.

I have already driven the car over 1000km since I purchased it (oil was changed before I purchased it) and took out the oil filter today to have a look for any rod bearings glitter or debris in the filter and found some large silver metal chunks in the filter (9 pieces total) which are not magnetic. Other than this, the filter and oil look fine and the car produces no strange sounds and drives completely normal, no error lights etc. I removed the pieces from the filter then drove it around my neighborhood and let it idle for a bit to see if any new pieces would appear but everything is clean. What do you guys think this could be?

To me it doesn’t look like rod bearing material as its quite large, non-magnetic, and the radius of these pieces don’t seem like the same radius of the rod bearings. My guess is that its debris from a stripped out thread? Maybe the oil drain plug since the oil was recently changed? In my previous 330i E92 I had basically identical debris in my filter from a stripped out camshaft retaining bolt so that’s why I’m guessing it may be from a stripped thread.

I would really appreciate some thoughts and opinions please. I’ll drive it for a couple more days and check the filter again for any debris.

Looks like the oil drain threads were stripped at one point and had a time sert installed and maybe they didn’t properly flush the shavings out, luckily the filter did its job.

Siajoon wrote

Looks like the oil drain threads were stripped at one point and had a time sert installed and maybe they didn’t properly flush the shavings out, luckily the filter did its job.

Yup, I think we cracked the case. I just took a closer look at the pieces and they have a distinct pyramid profile to it, like a thread… also arranged the pieces into a perfect circle and measured the inner diameter to be 10mm, which corresponds to an M12 bolt, which is what the oil drain bolt is.

Crisis averted 😅

For some reason I can’t attach the photo of the pieces arranged in a circle next to my tape measure…

maybe do an oil change sooner than usual to try and flush out any more small pieces that may have been left behind, although the filter will catch the left overs I would want to do an extra flush just to sleep better at night, these cars have there ways of keeping you up, haha!

Hopefully the drain plug isn't still stripped and it was repaired correctly, you'll find out next time you take the drain plugs out.

Also the story sounds like a load of BS, no one does all that labor to take rod bearings out to measure them, then reinstalls them saying they were "excellent".

tdott wrote

Hopefully the drain plug isn't still stripped and it was repaired correctly, you'll find out next time you take the drain plugs out.

Also the story sounds like a load of BS, no one does all that labor to take rod bearings out to measure them, then reinstalls them saying they were "excellent".

Yeah I agree, I don’t believe it. The bearings may or may not be original, either way the oil is not showing any indication of rod bearing wear so that’s at least a good sign. Although I know the proper way is to do an oil sample test or ultimately just change them, but I’m unable to find any oil sample test kits online in Europe.

noahmrv wrote

Yeah I agree, I don’t believe it. The bearings may or may not be original, either way the oil is not showing any indication of rod bearing wear so that’s at least a good sign. Although I know the proper way is to do an oil sample test or ultimately just change them, but I’m unable to find any oil sample test kits online in Europe.

I would not rely solely on an oil analysis as an indicator of rod bearing condition. I conducted a Blackstone oil analysis prior to replacing my original rod bearings, and it’s results were impeccable. However, the rod bearings were far from flawless themselves when removed at 48,000 miles.

I'm surprised those big chunks made it through the oil pick-up screen.