if the belt is dried and chappy (you can notice it from inner side of the belt) - time to change it...if noise will not stop - go for pulleys...but remember there are three pulleys...and you don't have to change all...take out the belt...scroll the pulleys...and replace ONLY which make a noise...

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Davud X5/110 - PITBULLET
Options: X5 4.4i, 07/2000
Modifications: 16:9/DVD Player “Absolute”/Style 177/BT Kit & Nokia Cradle for 6310i/Wheel Arch Moldings/4.6i Spoilers on Front & Rear bumps/35% Tint on Rear/Predator Angel Eyes/Full Black Grill/Xenon light on Low Beam/Facelift Tail lights/X-Pipe + MG-RACE Cat Replace/Green Filter/ Bosch Super4 Spark Plugs /Chrome Dash Rings/ Individual Black Carbon Roundels/Jlevis Silver Carbon Fiber Pedals.