What Causes Abnormal Noises in a Car Engine?
2 Answers
The main reasons for abnormal noises in a car engine are as follows: 1. If there is an abnormal noise during instant startup, but the noise disappears when the engine is idling: This issue is likely caused by a fault in the carbon brushes inside the starter motor. The working principle of the starter motor is that after being energized, the electromagnet engages the starter motor's gear with the engine's flywheel, causing them to rotate together and start the engine. Once the engine starts, the gear should quickly disengage. The abnormal noise in this case occurs because the starter motor's gear fails to disengage promptly, leading to grinding against the flywheel. Therefore, the starter motor needs to be inspected. 2. If there is an abnormal noise when the engine is idling after startup: This issue is likely caused by excessive clearance between the hydraulic lifters and valves inside the engine cylinder head. As the vehicle accumulates more mileage and ages, both the engine valves and hydraulic lifters experience wear. When the clearance becomes too large, a "ticking" noise may occur. To resolve this issue, the cylinder head needs to be disassembled to replace these two components.
My old car used to make this weird noise, sounded like metal fighting. Most of the time, a loose or worn-out belt will produce a squeaking sound, while a loose chain makes a rattling noise. Insufficient or dirty engine oil is also common, which can be detected by checking the dipstick. If the bearings are damaged, it’s often accompanied by heavy knocking sounds. If not addressed in time, a minor issue can turn into a major repair, multiplying the cost several times. I recommend checking the oil level monthly and having the mechanic inspect the belt and chain condition during routine maintenance. After all, driving safety comes first, and early maintenance saves both trouble and money.
