What Causes Loud Engine Noise During Car Startup?
2 Answers
The reasons for loud engine noise during car startup are: 1. When new engine oil is replaced, the engine may not adapt to the oil viscosity immediately, causing higher RPM and resulting in increased engine noise; 2. Coolant temperature is too low; 3. Engine knocking occurs; 4. After spark plug ignition, the remaining air-fuel mixture undergoes spontaneous combustion. Precautions for car startup include: 1. Walk around the vehicle to inspect its exterior and surroundings, checking for obstacles; 2. Examine the parking spot for oil or water stains; 3. Verify the condition of front and rear light assemblies; 4. Check tire pressure. The startup sequence for automatic transmission vehicles is: 1. Start the engine; 2. Shift to N (Neutral) gear; 3. Engage the electronic parking brake; 4. Shift to D (Drive) gear; 5. Press the accelerator pedal.
When the engine makes a loud rumbling noise just after starting, it's mostly due to insufficient oil circulation. This is especially noticeable in cold weather when the oil thickens like syrup, forcing the oil pump to work harder to distribute oil to all components. However, it usually quiets down after warming up for a few minutes, which is normal. If it still sounds like a tractor after warming up, you should check if the belt tensioner is loose or if there's an exhaust manifold gasket leak. My old car had a blown gasket last time, sounding like a broken horn at startup, but it became quiet immediately after replacement. By the way, using oil with mismatched viscosity for a long time can also make cold starts noisier.
