2008ml550_0104

Hi all. Dealer wants to charge a lot to replace a serpentine belt. I think it’s an 18 mm but which belt is right type. Speed sense steering one or without ? Appreciate if anyone can help diagnose why one belt has speed sensitive steering and the other sold at same store is not saying which type I have or which belt is right to use or if the pump is defective. Pump is new pump is not opwrwtibf at low speeds which suggest a incorrect belt or incorrect pump:detect and at low speeds idle low revs and I accelerate works great. Used CH 211S I think (green can) syn fluid.

Plutoe

look here-----Mercedes-Benz Electronic Spare Parts Catalogue Online