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      04-16-2011, 12:17 AM   #24

Drives: 2009 ///M3 E92 APW 6MT
Join Date: Dec 2010
Location: South FL

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2009 E92 M3  [0.00]
Originally Posted by BMRLVR View Post
Exactly what I am talking about!!!! You said your crank and main bearings were changed and the knock persisted. The cause of the knock and the bad bearings you saw out of your old engine were most likely not bad due to the bearings/crank themselves. It is quite possible the main bearing bores were out of round/tapered in your block which would cause bearing wear and noise and is also the reason why it persisted even after the bearings and crank was changed.

There are two proper ways to do repair a bearing/crank replacement on an engine diagnosed with bad main bearings.

1)Pull the engine out, put the bedplate back on the engine block, torque it down and then take measurements to verify everything is in spec. All of the new crank journals should also be measured to ensure they are in spec. Finally after this is done the bearings and crank should be installed, all mains should have plastigauge placed on them and the bedplate torqued. Once this is done and all of the measurements are within spec on the plastigauge, block and crank. You can be satisfied everything is ok. If this process is not followed then you are only assuming the block, crank and bearings is within spec. (The same process should be followed for the rod bearings, rods and journals but for the sake of this post I am only speaking about the mains)

2)The engine should be replaced with a complete long block. A long block will have all of the measurements I described above done during assembly so when you get it is "SHOULD" be good to go!

To me it seems that every dealer replacing crank and main bearings is not following the proper procedure and myself I would refuse to accept a dealer replacing crank and main bearings on my car without pulling the engine and verifying the block is within specs.
I'm just curious as to how you would go about asking a dealer to pull your engine and verify the block is within spec? I imagine the average dealer would tell you to take a hike.