Quote:
Originally Posted by JoeM3SSII
Quote:
Originally Posted by deansbimmer
Although thats a very unlikely scenario, if the crank wore all the way through the lead and copper to the steel substrate, then you'd probably hear some knocking and the bearing would gall/seize and spin right after. You wouldn't stop seeing copper or lead. The engine would fail first.
OP: Great job on the preventative maintenance. I know you're relaxing after a job well done, but with rod bearings in that kind of shape I would highly advise looking at the main bearings. If there is any lead or copper in the next report then consider them ticking time bombs.
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replacing main bearings is not a DIY it's more involved. Besides all what he did is to make himself feel better. There is no evidence that this type of bearing wear correlates with engine failure at all, the link only exist in people's mind not in reality. Each engine crank will leave its own footprint on the bearings. This is why the wear is not homogeneous from one bearing to the next. In other words he paid $$$ for a big placebo. The reason for this abnormal bearing wear is BMW design removed too much mass from the crankshaft and it vibrates and distorts too much. |
The reason for the bearing wear is inconsistent sizes from journal to journal. If you look at bearing pairs 1 and 5, 2 and 6, 3 and 7 and 4 and 8 you will notice they have somewhat similar wear patterns, this is due to the pairs on the larger journals having less clearance. One thing that has been shown is that BMW S65 Rod big end bores are fairly consistently sized, however crank journals tend to show more variance. My theory is that the tightest clearances (biggest journals) produced the worse looking bearings.