Last week end I noticed a new sound from my '96 960 immeadiately after starting it up. The sound came and went with the A/C compressor cycling. It seemed to be like a "hard working" belt so I first suspected a new serpentine belt was in order. Closer looks however found the idler on the tensioner had a small amount of play when I pushed on it and the fresh metal surface next to the belt looked a little dis-colored.

Last night I replaced it with a new one, $32, and took the grease seals off to look at the old one. What was left of the grease was pure black as if it had been heated to a very high temperature. The part of the bearing race that I could see still had some grease on it but the bearing felt funny when I spun it by hand. I guess it would have gone a few more miles but I think I got it just in time to prevent damage to the belt.

The new one still had a little play after mounting, but about half the amount of the old one. The noise seems to be gone.
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'96 965 with 16' wheels at 118K. Had '85 745 Turbo Diesel for 200K.