TM 5-3805-281-24-2
Crankshaft, Main Bearings, and Flywheel
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:
Oil starvation.
Contaminated oil.
Improper installation.
Engine parts failure.
Dirt between bearing and crankshaft journal.
Excessive heat.
Low oil pressure.
Poor periodic service.
Oil pump failure.
GALLED OR "WIPED" BEARINGS:
CRACKED, CHIPPED OR BROKEN BEARINGS:
Fuel in lubricating oil (incomplete combustion).
Coolant in lubrication system (cracked block, liner
Overspeeding.
Excessive idling.
seal failure, or leaking water pump seal with plugged
Lugging.
hole).
Insufficient bearing oil clearance.
Excessive oil clearance.
Parts not lubricated prior to engine operation.
Improper installation.
Wrong bearing size.
INCONSISTENT WEAR PATTERN:
RG,RG34710,1149
1923OCT971/1