What Causes Engine Noise During Cold Start?
2 Answers
Engine noise during cold start occurs because after the car has been parked for a day, the engine oil has mostly flowed back into the oil pan. Below are the reasons for engine noise during cold start: 1. During a cold engine start, the oil pump cannot immediately establish oil pressure or form an oil film between components. Particularly, the valves inside the cylinder head (upper part) lack lubrication during cold starts. Whether it's hydraulic lifters or mechanical rocker arms, there will be some valve clearance, resulting in a "ticking" sound. 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 "ticking" sound disappears (note: if the engine continues to make abnormal noises when warm, have it inspected at a repair shop as soon as possible). 2. Apart from oil-related issues, another component that can cause abnormal noise is the carbon canister purge valve. Its function is to open the electromagnetic valve between the carbon canister and the intake manifold after the engine starts, allowing the gasoline vapor adsorbed by the carbon canister to be drawn into the cylinders by the vacuum in the intake manifold for combustion. This not only reduces emissions but also lowers fuel consumption. However, this component can also produce abnormal noises during operation.
When there is abnormal noise during cold engine start-up, I believe the most common causes are issues with the belt system. For example, aging, slackness, or cracks in the timing belt or accessory belt can cause squeaking due to friction at low temperatures. Another factor is chain wear, especially in older models, where excessive clearance in the timing chain can produce rattling sounds. Insufficient lubrication is also critical—oil that is too thick or too low in quantity is more likely to cause problems in winter, as cold oil has poor fluidity, leading to dry internal bearings and abnormal noises. It is recommended to first check the belt tension and condition, replacing it immediately if worn. Additionally, using seasonally appropriate oil can help avoid more serious engine damage. Addressing these issues promptly can save significant costs.
