Symptoms: squeekin sound at idle, harsh sound on low speed (engaging AC I think). Tried the pulleys when loosed the belt and there was some free play on them both, mostly the lower one. Did not find new pulleys here fast enough for my 2007 (~100k miles) car so I just changed the bearings from the serpentine tensioner pulleys. The bearing size: 6203 (40x17x12mm) for the upper tensioner pulley. 6303 (47x17x14mm) for the lower idler pulley. I suggest to use quality bearings, not the £1 chinese ones. Remember to buy plastic shielded bearings. Procedure: 1. loosen belt 2. loosen 2 bolts holding tensioner (normal righthand threads) 3. separate tensioner from the engine 4. remove tensioner pulley (LEFThand threads) 5. beat the old bearings out with socket or similar 6. press new bearings, avoid scratching/damaging pulleys. press from outer edge (I used old bearing as a press tool). 7. put all back in reverse Belt can be left loose on its place while pressing if you don't change it also (recommended though).