Function of the car crankshaft
The crankshaft of an automobile engine is a core component of the engine, primarily functioning to convert the reciprocating linear motion of the pistons into rotational motion and output torque to drive the vehicle's transmission system and other accessories.
Power conversion: The crankshaft receives the linear motion force from the pistons through connecting rods and converts it into rotational torque, driving the flywheel and the transmission system, enabling the vehicle to move.
Driving accessories: The rotation of the crankshaft also drives auxiliary devices such as generators, water pumps, and fans through belts or chains, ensuring the normal operation of the engine.
Withstanding loads and balance: The crankshaft bears complex loads such as gas pressure and inertial forces, and is designed with balancing weights to reduce vibrations and ensure the smooth operation of the engine.
The crankshaft is one of the core components of the engine, responsible for converting the reciprocating motion of the pistons into rotational motion and outputting power. Once it fails, it will seriously affect the normal operation of the engine. According to recent authoritative public information (as of March 2026), the main manifestations, causes, and countermeasures of crankshaft failures are as follows:
Common symptoms of crankshaft failure
Difficulty starting: Wear of crankshaft bearings or damage to the journal causes difficulty in starting the engine.
Reduced power: The crankshaft fails to effectively transmit torque, resulting in slow acceleration and significantly reduced power output.
Abnormal noise: Metal friction sounds such as "buzzing" or "clicking" occur during engine operation, especially more pronounced during starting and acceleration.
Vehicle shaking: The crankshaft disrupts engine balance, causing obvious shaking at idle or during driving.
Increased fuel consumption: Reduced combustion efficiency and fuel consumption increase.
Engine overheating: Decreased oil pressure and affected cooling system, resulting in abnormal temperature rise.
Sudden engine shutdown: In severe cases, the engine may unexpectedly shut down during driving.
The engine fault light illuminates: The ECU detects an anomaly (such as loss of crankshaft position signal) and lights up the engine fault light.
Note: Some symptoms (such as the engine fault light illuminating, difficulty starting) may also be caused by crankshaft position sensor failure, which is an electronic signal issue rather than damage to the crankshaft itself.
Professional diagnosis is required for differentiation.
Common fault types and causes
Journal wear: Insufficient or deteriorated oil, presence of impurities, or improper clearance between the journal and the crankshaft.
Journal scratching/scratches: Poor assembly cleanliness, failure to change oil on time, or failure of the air filter, allowing impurities to enter.
Journal burn: Usually caused by a "welding" accident, with a bluish surface.
Cracks or fractures:
Commonly occur at the junction of the crank arm and the journal, or near the oil inlet of the connecting rod journal;
Causes include material defects, fatigue, overloading, failure of the shock absorber, and damage to the dynamic balance during welding repair.
Crankshaft deformation:
Heavy-load starting too quickly, sudden braking, or improper assembly.
Crankshaft seizing: Failure of the lubrication system, dry friction locking of sliding bearings.
Recommendations for response and prevention
Stop the vehicle immediately for inspection: Once the above symptoms occur, especially accompanied by abnormal noise, shaking, or inability to start, stop using the vehicle to avoid further damage.
Professional diagnosis:
Read the fault codes using an OBD device to determine if it is a sensor problem (such as P0335 related to the crankshaft position sensor codes);
If suspected damage to the crankshaft itself, disassemble for inspection of journal wear, cracks, and bending conditions.
Maintenance principles:
Minor wear can be repaired by grinding;
Cracks, fractures, and severe deformation usually require replacement;
After repair, perform dynamic balance correction and ensure the flywheel is installed balanced.
Preventive measures:
Regularly replace with oil and filter of the appropriate specification;
Avoid long-term overloading and over-speed operation;
Pay attention to preheating of cold engines, avoid sudden acceleration;
Strictly follow the specifications for assembly during maintenance to ensure clearance and cleanliness.
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