I just replaced both idler pulleys and the tension pulley this afternoon. I had heard some whirring/whining that changed with the engine speed and I suspected at least one of these pulleys so I pulled the front engine cover and checked them with a mechanic's stethoscope. One idler pulley was definitely noisey and another was questionable. The tension pulley was probably OK but I decided to order all 3 from Pelican and followed the instructions in Wayne's book (also online, with corrected torque specs). It was pretty easy and now I am going on a test drive!
I had replaced the serp belt about 6k miles ago and I remember reading a few cases where people had pulleys fail a while after putting on a new belt. Not sure if it was related, but I am happy nothing failed on the road and left me stranded.
