Reasons for abnormal noise during cold engine start?
2 Answers
Reasons for abnormal noise during cold start: 1. Oil lubrication: When a car is parked for a day, the engine lubricant basically all flows back to the oil pan. During cold start, the oil pump cannot immediately establish oil pressure to form oil films between components. Especially the valves inside the cylinder head lack lubrication during cold start, causing certain valve clearance in both hydraulic lifters and mechanical rocker arms, resulting in abnormal noise. 2. Charcoal canister solenoid valve: The charcoal canister solenoid valve opens the electromagnetic valve between the canister and intake manifold after engine start. This not only reduces emissions but also lowers fuel consumption, but may produce abnormal noise during operation.
I've also experienced abnormal noises during cold engine starts, especially noticeable in winter. The most common issue is related to engine oil—when temperatures are too low at startup, the oil becomes as thick as paste and can't flow properly, causing metal components inside the engine to grind dry and squeak. If you hear continuous tapping sounds, it's likely due to hydraulic lifters not getting oil in time or incorrect valve clearance. Belts are another usual suspect; when aged, they tend to slip and screech in cold temperatures, so check for cracks or looseness. A hissing sound from exhaust system leaks that disappears once the engine warms up is mostly caused by shrunken gaskets. So, before cold weather sets in, switch to low-viscosity oil, regularly inspect belt conditions, and if abnormal noises persist for more than ten seconds, promptly visit a professional shop to check the chain and timing system—don't let minor issues escalate into major problems.
