Benz Pulley Replacement - Credit to Bro Azamli et al
From Bro Shanon:
Add more to this. It is not necessary to change the entire part of the tensioner pulley. However you must take earlier action changing it when the tensioner pulley start making noise. Don't wait too long until the belt snap the pulley as shown in the video.
This will also save you minimum RM100 to just change rotary pulley alone (the spring attached to the pulley not necessary be changed if it is not damaged). I hope you understand what I tried to explain.
BTW, please open you bonet and listen carefully to the sound of your vehicle engine, it does carry some "meaning".