[JohnelP]

Yesterday I practically finished taking the engine apart. Why? Because I found copper like non-magnetic slivers in the oil filter. Took the oil pan off, and, extra bonus, found plastic debris from the timing chain guides. Given the upper oil pan gasket was leaking, i thought it is the time to take the engine out and see if I can fix it.

The problematic guides were the passenger side upper guide between the vanos phasors, and the smaller timing guide rail (not the one with the tensioner). They did not break, but the side part of plastic cushion of the rail began to disintegrate.

I continued the teardown to look for the metal scoring that generated the slivers. I was suspecting the rod bearings or the main bearings that could have copper, as everything else in the block is aluminum. And steel. I was a bit afraid a spun bearing is cooking, so, I removed the rod bearings, and I removed the crankshaft too to investigate the main bearings. Rod bearings have some wear on them, but no sliver type damage. Three have "spot"wear, but not disastrous. Main bearings were in good condition too. They are most likely from some aluminum alloy, as they are bright silver and do not contain any copper. So I am still puzzled. ....
Could not ind any spot where crank was scoring anything...

Continued to do some measurements. Got a cylinder dial gauge, and did measurements on the cyl bores. The top of the cylinder is severely out of round. The North-Sud direction is wider with 0.0015 " (15 thousands of an inch) = 0.038mm compared to East-West. That is three times the allowed 0.01 mm allowed bt manual.
Middle and bottom of the cylinder were within specs, and only 0.0005" out of round and same 0.0005" for taper
All the 4 cylinders on the passenger bank had exactly same measurement patterns. No exception. All cylinders are 3x allowed limit out of round on the top part of the cylinders.

I think that kind o explains why the car continued to consume oil (about a quart every 500 miles) even after the dealer did the valve stem seals work 10k miles ago... Did not do a leak down test, because I was not expecting this..

I was thinking to look for a machine shop to bore .0015" and restore the bores in standard sizes, without getting to oversized class. Have not searched any machine shop, but i understood there are not many that could bore hyper eutectic Alusil blocks. And even if I can find one, I would need to get new rings sets, assuming i can still keep the pistons. Given a piston ring set is 100$, i will spend 800$ only on rings. Adding the bearings, head gaskets, all bolts I am getting to the point where BMW remanufactured gets a better deal.

If I go with remanufactured, will the dealer be honest enough to pay me back the core charge? They say they pay the core charge only if the engine I send is rebuildable. Don't feel very comfortable, given they can find any gimmick to say your engine is not rebuildable. Plus, I need it delivered to residential address, and beyond the 1k $ shipping charge, they add that fee on top.