Here's a new one for me.

I replaced all the belts on my 1987 420SEL a few weeks ago. This would be the air pump belt, the ac belt, the alternator belt, and the two ps belts.

Last week, the alternator belt rolled over. I figured I probably made it too tight, as that is easy to do with the set up. So I tighted it up a little less.

Yesterday, all the belts came off! None damaged.

The accessories all turn freely, the pulleys are in fine condition, there's nothing in the grooves, none of the bearings on the pulleys are loose or wobbly.

Any idea what is going on?

I'm thinking I am making the belts too tight or too loose. Does somebody have a detailed procedure I can review?

I must have put a few hundred v-belts on in my life and have never had anything like this happen.

Thanks in advance!

__________________
Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport