Found Metal in Oil Filter – What’s Ferrous Besides IMS Bearing?

[DAB986]

Just joined the forum recently and came across your post on metal contamination. I have a '98 as well--silver with red interior.

Since it is now July, I assume you've already found the cause of the metal contamination in the oil. Hopefully, it ended up not being too big of an issue, but given the lab results, my first thought was that (in addition to one or more of the other previously mentioned issues in this thread) you might be seeing the initial stage of bore scoring, or at least wearing of the iron coating on the pistons that ultimately leads to bore scoring. At this point, it might not be bad enough to see increased smoke in the exhaust.

I believe a lot of people would be interested in your findings, and how it was resolved. Also, have you ever run a diagnostic on the car to look at the history of potential engine over-revs? Though bore scoring is a potential issue with any high mileage M96/M97 engine, it is my understanding that the early M96 engines tend to be less prone to it (as well as de-chunking) because they have a shorter stroke than the later engines and use cast aluminum pistons, which have a more robust iron coating than the forged pistons found in the later engines.

[997_986]

Originally Posted by DAB986

[...] it is my understanding that the early M96 engines tend to be less prone to it (as well as de-chunking) because they have a shorter stroke than the later engines and use cast aluminum pistons, which have a more robust iron coating than the forged pistons found in the later engines.

No, the reason these "low power" M96 engines do not suffer from scoring is due to the fact that their cylinder walls are thick enough and cooling sufficient. The concept was not bad at all. The problems began with ever larger displacements and thinner cylinder walls in combination with inadequate cooling.

Please do not start a "scoring thread" ;-)