What Causes the Ticking Sound During Cold Engine Start?
1 Answers
When a car is parked for a day, the engine oil mostly flows back into the oil pan. During a cold engine start, the oil pump cannot immediately establish oil pressure or form an oil film between components, especially for the valves inside the cylinder head (upper part). Without proper lubrication, both hydraulic lifters and mechanical rocker arms will have some valve clearance, resulting in a ticking sound. More details are as follows: 1. After the engine runs for a while, oil pressure is established, an oil film forms, and the oil temperature rises. Once the engine operates normally, the 'ticking' sound disappears (Note: If the engine consistently makes a ticking noise when warm, it is advisable to visit a repair shop for inspection as soon as possible). 2. Apart from oil-related issues, another component that can produce a ticking sound is the carbon canister purge valve. Its function is to open the solenoid valve between the carbon canister and the intake manifold after the engine starts, allowing the gasoline vapors adsorbed in the carbon canister to be drawn into the combustion chamber under the vacuum of the intake manifold. This process not only reduces emissions but also lowers fuel consumption, and it may also produce a ticking sound during operation. (Additional note: Poor-quality engine oil can sometimes cause the engine to make a ticking sound.) Therefore, a ticking sound during a cold engine start is not a malfunction. However, if this abnormal noise occurs when the engine is warm, attention is needed. Some luxury car engines may also exhibit this phenomenon during cold starts.
