Quote:
Originally Posted by JonEQuest
I'm sure when I get the engine totally apart all find embedded aluminum making the crank bearings tight which is why the engine still offers a lot of resistance to turn over with the cams and oil pump removed. I even have all of the rod bolts loose and the number 3 bearings completely removed of course. Luckily it's not seized. This is just another testament to these engines requiring high quality oil of the proper weight that is changed very often.
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Do you have the spark plugs out? If not, you will be fighting cylinder compression.
Cause/effect is the hard part with tearing down the engine. Shits busted everywhere but what happened first? Need an actual engineer inspecting tons of engines to draw any conclusions. First hand, I've torn down a handful now and it has been different every time. This one looks like knock/detonation pounded the bearing:
Crank looks like it fared extremely well. Upon closer look, there appear to be heat cracks on the journal surface. The rod itself also took a ton of heat and abuse, but, I am going to try to get it running again with fresh bearings and some sandpaper. Plasti-guage came back between .0015" and .002" as measured from a few different places in the journal which is adequate.
If this "repair" doesn't work I'll tear it down and rebuild it with replacement parts. That was the initial plan. I just wanted to show a video of what this actually looks like for those that think they can slap a new set of bearings in and move on. There is more damage there than just the bearings. Rod is probably outside of BMW's tolerance for roundness and crank journal surface is probably developing cracks. These aren't N55 issues... this is something that happens on any engine that spins a bearing. I made the video more for informational purposes so people can see an example of a spun bearing, what the other bearings look like, and what type of damage to expect.
Part two would consist of sanding the journal and and checking the clearance. Making videos is pretty annoying though so I don't plan on making a diy on how to sand a journal. Use common sense. If you need a diy on how to use sand-paper and polish something then this repair may not be for you.