u/Rich-Skirt8952

I need help with my S203 C200 CDI from 2006 with 254000 km. I have a strange sound while accelerating, it only occurs with a certain amount of load, when the engine is idling or with less throttle you can't hear it. I also can't replicate that sound while revving in neutral standing. I thought it was a squeaky belt and/or old idler pulleys which i replaced immediately (water pump included) but the sound stayed. I hope you can hear it in the video and somebody can help me. Cheers ✌🏻