Why does the Mercedes-Benz make a loud noise when starting?

[OBraxton]

Mercedes-Benz makes a loud noise during cold starts because the arrangement of the exhaust manifold places the catalytic converter too far back. The catalytic converter must reach a certain temperature to effectively filter exhaust gases. Therefore, to quickly heat up the catalytic converter, the exhaust valve closure is intentionally delayed during cold starts, causing the air-fuel mixture to enter the exhaust manifold and combust, resulting in the loud noise during cold starts. Here is some related information: History of Mercedes-Benz: Mercedes-Benz was founded in 1926 by Karl Benz and Gottlieb Daimler. Its predecessors were the Benz & Cie. and Daimler-Motoren-Gesellschaft, established in 1886. The two companies merged in 1926 to form Daimler-Benz AG. Mercedes-Benz Logo: The Mercedes-Benz logo is a three-pointed star, symbolizing the ambition to dominate land, sea, and air. This emblem was created after the merger of Daimler and Benz. The original Daimler logo featured a three-pointed star, while the Benz logo had the word "BENZ" inside a double circle. After the merger, the Daimler-Benz logo became a three-pointed star inside a single circle. Making the three-pointed star shine globally has been Mercedes-Benz's dream for over a century and remains its relentless pursuit.

[LenaRose]

The Mercedes-Benz starts with a loud noise, I remember my own car was like this, roaring at startup as if the engine was protesting. The main reason might be insufficient oil pressure during a cold start, causing the engine to require more horsepower to start, resulting in louder noise. Also, if the belt is old and loose, it squeaks and is particularly annoying. If the exhaust pipe is leaking or the welding points are loose, the vibration and noise during startup will increase. I suggest warming up for a few minutes when it's cold to let the oil temperature rise before driving, which can reduce noise. Additionally, the Mercedes-Benz exhaust system is designed with precision, so any leakage will make the sound more noticeable. Check if the exhaust pipe gasket is aging. Don't take loud noises lightly; long-term neglect could damage engine components. It's best to record the startup sound with your phone and let the mechanic listen to it, using a stethoscope to diagnose the issue, to avoid unnecessary expenses on random part replacements. Addressing small problems early can save you from bigger troubles. Mercedes-Benz parts are expensive but reliable in quality.

[SanArthur]

As a young car owner, I searched online for the causes of Mercedes-Benz startup noise. Common issues include exhaust pipe leaks or damaged engine mounts, causing severe vibrations during startup. Some netizens mentioned that a loose pulley belt can cause squeaking, and replacing the belt can restore quietness. The Mercedes-Benz air conditioning compressor also generates noticeable noise when starting up, especially when cooling in summer. It's recommended to conduct a simple self-check first—listen to whether the noise comes from the front or rear of the car during startup. Noise from the front suggests engine-related issues like oil pump problems, while noise from the rear indicates exhaust pipe faults. Avoid tampering with high-pressure components yourself; instead, visit a professional repair shop to scan for trouble codes accurately. Many forum users share that OBD diagnostic tools are affordable, and buying one to read preliminary data can save on diagnostic fees. Prolonged noise issues may affect driving comfort. Although Mercedes-Benz repairs are expensive, the original manufacturer service offers reliable guarantees.

[RyderRose]

Having repaired Mercedes-Benz vehicles for many years, a loud startup noise is most likely due to belt wear or insufficient oil supply from the oil pump. A normal cold start may produce a few rumbles, but if the noise persists, check for leaks in the exhaust system—leak points with significant vibration can cause noise. An aging belt slipping will produce a squealing sound and can easily damage other components. The air conditioning compressor also generates extra noise when starting under heavy load, especially on hot days. Simply replacing the belt costs just a few dozen dollars, but exhaust issues require welding or replacing gaskets at a higher cost. Don’t ignore changes in noise—early diagnosis can prevent secondary failures and save money and time. Mercedes-Benz vehicles are precision machines, so taking them to a professional shop for inspection is the right approach.