I'd check to make sure the pulley is not out of round or bent.

Tzung-Horng Yang wrote:

 Hi Volks, I am back to California (San Diego) and am glad to join to this list again. I have a rare (?) problem about my alternator cradle bracket. In late July while I was still in Denver, CO, I had a noise coming from the engine compartment and the van vibrated pretty badly. The VW dealer mechanics found the barckets of the alternator were broken and replaced them. Yesterday, the same problem happened. Strange enough, I looked through all the repairing records, and found previous owner had done the same repairment once (only the cradle barcket not the support one) at about 60 K (it is 86 K now). I searched the archives and find no clues. I remember the old German mechanics at VW dealer in Denver told me that he has not seen this problem before (actually I had to do special order for the barckets). Does anyone have any similar problem occur to them or any idea what might be wrong with my car? Thank you for all your help. Tzung Yang 1990 VW Carat Vanagon