What's the reason the crankshaft won't turn?

[McHazel]

When starting the engine, if the starting system is intact and the transmission is in neutral position, pressing the start switch results in the starter making noise but the crankshaft fails to rotate, this indicates a mechanical failure. Below are relevant details: Poor engagement between starter and flywheel gear: The ring gear and starter gear may collide during engine starting, causing tooth damage or unilateral wear. If three or more consecutive teeth are damaged or severely worn, the starter gear and ring gear teeth will have difficulty engaging. Cylinder sticking: When the engine is shut down at excessively high temperatures, heat cannot dissipate properly, causing the piston rings and cylinder to stick together under high temperature, making it impossible to start after cooling. Crankshaft seizure: Due to lubrication system failure or lack of engine oil, dry friction occurs in the sliding bearings, eventually leading to crankshaft seizure and failure to start.

[EmiliaDella]

When encountering the issue of a crankshaft that won't turn, I believe the most common cause is internal engine seizure, such as piston and cylinder liner adhesion. This typically occurs due to insufficient or poor-quality engine oil. In my younger days, my car experienced this - it wouldn't start after parking, and upon inspection, we found the engine oil had completely leaked out, causing the piston to seize the crankshaft tightly. Ultimately, we had to disassemble the engine for a major overhaul. Additionally, burned-out crankshaft bearings or bearing shells can also prevent rotation, especially after high-speed operation without timely cooling system maintenance. Other possibilities include bent connecting rods, external tools jammed in the flywheel hole, or metal deformation after severe overheating. Most importantly, never force it with a wrench to avoid damaging more components - it's best to tow it to a professional repair shop for thorough inspection. Regular maintenance with frequent oil changes and avoiding overloading the engine during hill climbs can significantly reduce these risks.

[LaPresley]

A seized crankshaft is indeed a headache, likely caused by insufficient lubrication leading to mechanical jamming. I've experienced this with older cars - when the oil ran dry, the pistons got completely stuck and wouldn't budge. It could also be bearing failure or crankshaft deformation, requiring professional disassembly for inspection. Additionally, check the starting system first: verify if the battery is drained or if the starter motor is stuck, as these are sometimes mistaken for crankshaft issues. If water entered the engine, hydraulic lock can cause pistons to seize mid-stroke, requiring internal water removal. I recommend not delaying - contact a repair shop immediately and avoid forcing rotation yourself. For prevention, regularly checking oil level and quality is crucial. Maintaining proper engine temperature is also key, especially for overheating vehicles.

[VanVanessa]

A crankshaft that won't turn often indicates internal issues like piston seizure or bearing failure, typically caused by lubrication failure. Check the dipstick for dry oil or metal shavings indicating wear. External factors like an unremoved flywheel locking tool could also be the cause. Avoid forcing it to prevent breakage - have a mechanic test it with a barring tool. Don't neglect regular oil changes.