Basic Troubleshooting
WARNING: This page is about a different car, the 2004 Mercedes-Benz C230 and 2003 Mercedes-Benz C230. However, it is still accessible from the selected car via links, so may be relevant.
If starter is noisy, the cause could be bent or damaged gear tooth chamfers on ring gear. This cannot be seen with starter installed in vehicle. Activate starter without switching ignition on. Metallic noise should not be heard. If noise is heard, replace ring gear.