Quote:
Originally Posted by Watermelon6161
Unfortunately, today when I planned to replace my 09 E90M3 with 130,000 kilometers on it, I discovered scratches on one of the crankshafts, clearly caused by metal shavings. What should I do? Do I need to replace the crankshaft? I'm devastated.
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That type of damage is problematic, and would certainly necessitate engine removal for replacement of the crankshaft for a correct repair. With that said- that type of damage has resulted from imperfections in the crankshaft and created valleys in the hardened layer of the crankshaft. The damage is not proud of the journal's surface like most type of scoring. The journal *can* still function if needed, and obviously has remained functional since the damage occurred.
The best route is removal and rebuild. However if that is not possible and you feel adventurous or in an experimental mood, I would check the journal carefully and confirm there are no proud gouges, clean it up as best as possible and install new bearings. Reassemble and see how long you can go. You might be surprised how many more miles the engine will go.