Just now going thru replacing deflector pully and adjustment pully. Go to youtube look up bmw idle pulley diy. There are a few vids about these pulleys with some instruction on how to know if they are bad. My adjustment pulley would free spin and make the marbley noise indicating the grease was gone and bearings about to fail. The deflector on top was almost seized. The car was making a lot of noise and i caught it before it thru the belt. Maybe this is your prob. Replacement parts not that bad, see my post mechanical vs hydraulic pulley, and my indie was going to do it for $100. But i decided to do it my self. I am no mechanic but found it very easy to do. Getting the fan off was the worst prob and with all the instruction on this site, that was not a big deal.
The crankcase vent valve i did also. Little bit bigger job but again great instruction here and there is also a guy that videoed the whole process on youtube! I love these two sites, saved me a LOT of money.
Let me know if i can help but there are a lot of more knowledgable people here.