What is the solution to the knocking sound during cold start that disappears after the engine warms up?
3 Answers
The solutions to the knocking sound during cold start are as follows: 1. The knocking sound disappears as temperature rises: When the car starts and knocking sounds occur in low-temperature environments, but disappear as the temperature rises, this type of knocking can be temporarily ignored, and the vehicle can continue to be driven. 2. The knocking sound becomes more obvious at normal temperature: If the knocking sound does not disappear but becomes more pronounced when the engine reaches normal temperature, the owner should avoid high-speed driving, stop and inspect the vehicle in time to prevent traffic accidents. 3. Replace the cylinder liner, piston, and piston rings: If after removing the cylinder head and pulling out the piston, it is found that the cylinder is severely out of round, scratched, or the gap between the piston and cylinder is too large, replacement is necessary. Replace the cylinder liner, piston, and piston rings.
My own car often has knocking sounds during cold starts, which disappear once it warms up. At first, I was quite worried that the engine might be damaged. Later, I learned to check the engine oil condition and found that the oil was a bit thin and aged. After switching to a more suitable 5W-30 full synthetic oil for low temperatures and regularly maintaining the oil level, the issue improved significantly. Additionally, I made sure to use high-quality 92 or 95 octane fuel to avoid knocking caused by poor-quality fuel. If this doesn’t work, it’s worth checking the ignition system, such as worn spark plugs or incorrect ignition timing. Occasionally using fuel additives to clean carbon deposits can also help. If the problem persists, it’s best to visit a professional shop to test fuel pump pressure or piston clearance, as long-term neglect could damage the engine’s core components. Regular maintenance is key—I recommend a quick oil check every season to prevent issues and save money in the long run.
In the car repair community, dealing with cold start noise is quite common, usually caused by insufficient cylinder wall lubrication due to poor oil flow when the engine is cold. The first step is to immediately check the oil level and quality—if it's too low or too thin, quickly switch to a thicker oil. The second step is to try replacing the spark plugs or adjusting the high-voltage wires, which can reduce knocking sounds. If the noise persists, don't overlook internal issues, such as worn piston rings or excessive connecting rod clearance, which may require engine disassembly for inspection. Regular use of oil additives can enhance protection, and always ensure the fuel is genuine. If the noise disappears after the engine warms up, it indicates a manageable issue, but it should be addressed promptly to prevent worsening wear. I recommend visiting a reliable repair shop to scan for fault codes with a diagnostic computer—early detection saves money. Simple maintenance can also extend the engine's lifespan.
