What are the phenomena and causes of crankshaft axial movement noise?
4 Answers
Phenomena and causes of crankshaft axial movement noise can be divided into two situations: axial and radial. Axial phenomena and causes: Excessive axial clearance causes vehicle jerking during startup, sometimes accompanied by metallic impact sounds. Diagnosis involves using a pry bar under the vehicle to check for play at the crankshaft pulley. The root cause is typically excessive wear of crankshaft thrust washers requiring replacement. Radial phenomena and causes: Metallic impact sounds and engine vibration occur during acceleration/deceleration. Using a stethoscope (automotive diagnostic stethoscope or 2-3 foot long copper pipe/iron rod), listen near the engine bottom. Subsequent inspection involves checking engine oil for metal particles - 90% probability indicates excessive crankshaft bearing clearance causing abnormal noise. For precise diagnosis under favorable conditions, removing the oil pan provides more accurate assessment.
My car recently made a rattling knocking sound during cold starts, with the noise becoming more noticeable during acceleration or uphill driving, like metal blocks colliding inside the engine. I took it to the repair shop for inspection, and the mechanic explained that this was caused by the crankshaft moving back and forth excessively, resulting in abnormal noise due to excessive looseness. The reason was severe wear of the thrust washers or insufficient lubrication, leading to excessive axial clearance. This condition is common in older vehicles or those frequently driven under high loads. The mechanic warned that if the worn parts are not replaced promptly, the crankshaft could collide with the cylinder block or pistons, leading to catastrophic engine failure and skyrocketing repair costs of thousands of yuan. This made me realize the importance of regular maintenance and lubrication. I advise car owners to seek professional diagnosis as soon as they hear similar sounds, rather than procrastinating like I did.
As a technician who frequently repairs cars, I have encountered countless cases of crankshaft end play noise. The symptom is a rhythmic knocking sound during engine operation, often worsening at low RPM or idle, sounding like a dull thud. The root cause is uncontrolled crankshaft axial clearance, usually due to thrust bearing wear, gasket failure, or incorrect installation. Wear mostly stems from poor lubrication or excessive speeding. Inspection can be done with simple tools to measure clearance, while repair requires replacing parts and adjusting the gap. Ignoring it not only makes the noise annoying but also accelerates crankshaft deformation or even fracture, endangering driving safety. Now when repairing cars, I always remind customers to pay attention to changes in engine sounds—early intervention saves money and hassle.
After playing with cars for so long, I often see complaints about engine noise in car enthusiast groups. The abnormal sound of crankshaft axial movement feels like this: a buzzing sound at startup, turning into a metal friction sound during mid-to-late driving. The cause is usually worn thrust washers, which allow excessive front-to-back movement of the crankshaft. This kind of failure is mostly caused by poor maintenance or aggressive driving. Ignoring it not only creates noise, but the loose crankshaft can damage other engine components, making repairs extremely expensive. When modifying cars, I recommend first checking the lubrication system. If abnormal sounds are detected, take it to the shop immediately instead of messing around. Safe driving comes first—don't let your beloved car develop major issues.
