What Causes Loud Engine Noise During Car Startup?
4 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.
Does your car sound like a tractor every time you start it? It might not just be due to cold weather. I've encountered a similar situation before—after taking it apart, I found the starter motor's gear wasn't engaging properly, producing a particularly harsh grinding noise. Another possibility is loose screws on the underbody shield, causing the engine vibrations to make the metal panels rattle. My advice is to pop the hood first and listen for the source of the noise. If it's a buzzing sound from the middle section, chances are it's the alternator bearing wearing out. Last time during a dealership service, the technician mentioned that such abnormal noises shouldn't be ignored—early diagnosis can save you big money. By the way, cars with modified exhaust systems will naturally have louder startup sounds, which isn't considered a fault.
Starting noises can be divided into high-frequency and low-frequency types. A dull low-frequency sound usually indicates aging exhaust hanger rubber bushings, causing excessive shaking of the exhaust pipe. A sharp high-frequency noise requires focused inspection of the starter motor, as worn carbon brushes can produce a drill-like sound. Last winter, my car always made a clattering noise during startup, which was later diagnosed as insufficient oil pressure in the VVT sprocket. Switching to higher-viscosity oil significantly improved the issue. Additionally, when the battery is low on charge, the starter motor struggles to turn, resulting in louder noises. Don’t ignore abnormal sounds—many minor issues can escalate into major engine overhauls if left unattended.
