Causes of crankshaft failure include vibration, insufficient lubrication, an over pressurized cylinder or cracks. The majority of steel crankshafts fail because of fatigue failure, which starts at the change of a cross-section in the crankshaft.
A heavily vibrating vehicle may experience a crack in the crankpin or journal, especially if the vehicle has torsional vibration, leading to crankshaft failure. Insufficient lubrication causes the bearing in the crankshaft to fail. An over pressurized cylinder occurs when the crankshaft's liner has a water leak and the safety valve does not work. The pressure causes the crankshaft to slip or bend. Cracks most commonly occur at the fillet between the journal and the web on the crankshaft.