Re: overheat-knocking noise
and I meant to explain further.... over heat causes a normally round piston to distort and become "squarish", it then begins to seize in the round cylinder bore. As it seizes, it welds itself to the cyl. wall (adhesion). Then bits of aluminum will be knocked off by the rings, and into the oil (and the filter). With continued running, the piston may break, sending the now loose con rod flailing around and usually then "windowing" the block. But, if the pistons live, the contaminated oil finds it's way into the oil passages of the crank. Additional debris from bearings ends up clogging the lube passages. The con rod bearings are the last in line of the "cascade" delivery system. The brg. runs without lube until it begins adhesion with the crankshaft. The heat often causes the brg. to melt and it extrudes out of the journal and into the pan.<br />The pan removal is labour intensive to see the damage which is why a filter cut is done.
