What causes the rattling sound when the car is running?

[VonSilas]

Possible causes of rattling sounds while the car is running are as follows: 1. Engine oil issues: Using low-quality engine oil, not changing the oil for a long time, or insufficient oil can easily increase friction between the valves and guides, as well as hydraulic lifters, making various sounds in the engine louder. 2. Engine issues: The rattling sound is usually caused by valve noise, excessive valve clearance, or wear, resulting in metal impact sounds. Some cars may produce this sound when cold-starting due to poor lubrication, excessive wear of pistons and cylinder walls, leading to gaps exceeding normal tolerance ranges, causing piston and cylinder wall collisions during engine operation. 3. Excessive carbon deposits in the engine: First, try carbon cleaning through no-disassembly cleaning or high-speed driving. If ineffective, the engine may need to be disassembled for carbon cleaning. 4. Tire issues: When driving on highways with windows open, a noticeable "rattling" sound from the body may indicate stones stuck in the tires. Safely pull over to the right and check the tires if possible.