CRANKSHAFT AND MAIN BEARING FAILURE ANALYSIS
Misaligned or bent connecting rod.
SCORED MAIN BEARING:
Warped or bowed crankshaft.
Distorted cylinder block.
(Diagnosis also applies to connecting rod bearing.)
BROKEN MAIN BEARING CAPS:
Engine parts failure.
Dirt between bearing and crankshaft journal.
Low oil pressure.
Poor periodic service.
Oil pump failure.
Coolant in lubrication system (cracked block, liner
seal failure, or leaking water pump seal with plugged
Insufficient bearing oil clearance.
Excessive oil clearance.
Parts not lubricated prior to engine operation.
Wrong bearing size.
INCONSISTENT WEAR PATTERN: