I had the valve cover off during the compression test, the O ring probably bounced near the valve gear and was washed to the bottom of the crankcase. This O ring is 1/2 the size of the oil filter stem o_ring.

I tried cracking the lines, there was no appreciable change when I cracked the #3 line.

There was NO sign of bearing debris in the bottom of the oil pan when I removed it, it's likely none was in the drained oil either. There would have been a trail of swarf running into the center hole of the drain pan.
That didn't happen.

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Nate Stanley
(Currently Benzless)
1985 F-250 6.9l 170K
2009 SCION XB 36.5K
2003 LS430 78K
2012 Kubota B 2320