What Causes Abnormal Noise During Engine Idling?
3 Answers
Engine idle abnormal noise may be caused by the following reasons: Timing chain elongation, tensioner pressure loss, balance shaft wear: Timing chain elongation is generally caused by metal fatigue. After prolonged driving combined with the high-temperature working environment of the timing chain, elongation can easily occur, leading to abnormal noise. The tensioner is connected to the oil passage and adjusts the tightness of the timing chain through oil pressure. If the tensioner oil passage is blocked or the internal check valve loses pressure, the chain may loosen and produce noise. The balance shaft is used to reduce vibrations generated during engine operation. If the balance shaft oil passage is blocked, it can increase wear on the journal and bearings, resulting in noise. Camshaft, crankshaft, and connecting rod bearing wear: If the vehicle uses low-quality oil, excessive sludge may form in the engine, blocking the lubrication oil passages and preventing oil from reaching components that require lubrication and cooling. This can cause wear on the camshaft, crankshaft, and connecting rod bearings, leading to noise. Additionally, if the engine lacks coolant, causing excessive engine temperature, the above phenomena may also occur. In severe cases, it can even lead to cylinder scuffing or bearing seizure. Increased timing variable wheel clearance: Variable valve timing can adjust according to engine speed and operating conditions, typically using hydraulic control to advance or delay the camshaft timing gear's internal rotor by a certain angle. If the variable timing wheel's internal rotor is stuck or the oil cavity is worn, the clearance may increase, causing noise. Excessive valve clearance or damaged rocker arm: The rocker arm is a lever mechanism that presses the valve, and the valve clearance is mainly controlled by the hydraulic lifter. Damage to either can result in valve noise.
I've experienced abnormal noises from the engine during idle, which are usually caused by belt issues, such as a loose or worn alternator belt or water pump belt. When the vehicle is idling, the low engine speed makes the belt prone to slipping, producing a squeaking sound that resembles a mouse gnawing. Long-term neglect can cause the belt to break, leading to engine overheating or even a breakdown. It's recommended to first check the belt tension by gently pressing it to see if it's too loose. If the belt is aging and shows surface cracks, it should be replaced—saving money and hassle. Regular cleaning of the engine compartment and avoiding dusty roads can extend the belt's lifespan. Increasing noise could also be related to other components like the power steering pump, so it's best to consult a professional mechanic promptly.
My car made a ticking noise at idle. At first, I thought it was an exhaust leak, but it turned out to be the sound of worn connecting rod bearings. The noise is more noticeable at idle when the engine vibration is minimal; if you accelerate and increase the RPM, you might not hear it anymore, so you need to be careful. Ignoring connecting rod issues can lead to major trouble, causing internal engine damage and eventually total failure. In my case, spending some money to replace the bearings solved the problem. Regularly checking the oil level is crucial—low oil increases friction and abnormal noises. For older cars, it’s best to schedule periodic engine diagnostics to detect potential defects early. Don’t ignore small noises; they’re often early warning signs.
