M013 serpentine tensioner - weak tensioner bolt threads?

[Mike Richards]

I realize this area has been covered a great deal.

"someguyfrommaryland" responded today in a post titled "W124 Serpentine/Bearing Question". He indicated that the threads on the tensioner were a weak spot.

My vehicle is a 1991 300-SEL. The procedure outlined in the maint manual for loosening the 19mm bolt 1/2 turn has always been followed. I've had the belt off/on 3-4 times in as many years. The last time I was snugging things down, the 13mm threaded bolt seemed to strip - it lost it's hold; then I'd begin to tighten it down again and it would keep tension for just a bit before it slipped again.

Can I merely renew this bolt and the bracket it goes through or do I have to buy the entire tensioner assembly, etc., etc.?

Also, would it hurt next time to maybe loosen the 19mm bolt a little more than the 1/2 turn stated in the manual? Loosening 1/2 turn doesn't seem to give it much slack?

Thanks ahead of time for your thoughts.