Look for conditions that could hinder performance or safety, such as (but not limited to) oil, coolant and fuel leakage, blocked events, loose or missing hardware, and electrical connections.
Visually inspect the fan belt for cracks, fraying, stretching, and verify the belt is properly seated in the pulley grooves. Replace the belt according to the engine manufacturer's recommendations.
Note: At the 500 hour or 12 month service interval, it is recommended that the belt be removed and checked for wear. While the belt is removed, inspect pulleys and bearings. Rotate and feel for hard turning or unusual sounds. If pulleys and bearings need replacement, contact the engine manufacturer.
Source: MaintainX (Community Member)