Bearing failure: Symptoms include a muffled sound, as if the load has suddenly increased and the engine speed has decreased, oil pressure has dropped, and black smoke is emitted from the exhaust. Bearing failure will cause the bearing shell and journal to seize up, resulting in engine shutdown. The main cause is the destruction of the lubricating oil film on the bearing shell surface, leading to direct metal-to-metal contact between the bearing shell and journal, rapid increase in friction temperature, and subsequent seizure.
Troubleshooting: Immediately stop the machine, remove the cover, inspect the connecting rod and bearing shell, identify the cause, and repair or replace them.