What Causes Engine Noise During Cold Start?
3 Answers
Engine noise during cold start occurs because after the car has been parked for a day, the engine oil has mostly flowed back to the bottom of the engine. During a cold start, the oil pump cannot immediately establish oil pressure or form an oil film between components. The valves inside the cylinder head lack lubrication during cold starts, resulting in some valve clearance whether it's hydraulic lifters or mechanical rocker arms, which causes the noise. After the engine runs for a while, oil pressure is established, the oil film forms, and the oil temperature rises. Once the engine operates normally, the noise disappears. Apart from oil-related reasons, another component that can cause noise is the carbon canister solenoid valve. Its function is to open the solenoid valve between the carbon canister and the intake manifold when the engine starts, allowing the gasoline vapor adsorbed by the carbon canister to be drawn into the cylinders under the vacuum of the intake manifold to participate in combustion. This not only reduces emissions but also lowers fuel consumption, but it can also produce noise during operation.
As a veteran driver with over a decade of experience, I've seen plenty of cases of abnormal engine noise during cold starts. The most common culprit is aged belts—when the rubber hardens, the friction between the belt and pulleys during cold starts produces an annoying squealing sound. Engine oil is another critical factor; if it's too viscous at low temperatures, lubrication lags, causing dry friction and noise inside the engine. The problem worsens if the oil hasn't been changed in too long or has the wrong viscosity. Poorly adjusted valve clearance or a stretched timing chain can also cause a rattling noise, especially during winter when temperature fluctuations are significant. I remember replacing the belt and switching to season-specific oil before last winter, and the noise disappeared—I'd recommend checking these components before minor issues escalate into major engine repairs. Seasonal transitions demand extra attention to maintenance; short trips can lead to carbon buildup, and incomplete combustion during cold starts exacerbates noise. Comprehensive maintenance is key—skimping on small expenses now might lead to hefty bills later.
As a new car owner, the abnormal noise from the engine during cold starts makes me quite nervous. I've done some research and learned that it's mostly due to a loose or worn-out belt—squeaking belts in cold air are common. It could also be that the engine oil's viscosity changes in low temperatures, leading to insufficient lubrication and increased engine noise. My car often does this in winter. I've tried applying some lubricant to the belt as a temporary fix, but it's not a long-term solution. Old or mismatched oil viscosity can worsen the problem, especially during seasonal changes when the noise becomes more frequent. Later, after switching to winter-grade oil, the situation improved. For prevention, maintaining proper oil levels and regularly checking belt wear are essential; otherwise, prolonged neglect could damage the engine. Safety first—I've learned to start the car slowly and let it warm up for a few minutes when there's abnormal noise to avoid the risk of a breakdown.
