M013 serpentine tensioner - weak tensioner bolt threads?
 

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.

The tensioner rod is replacable as a seperate item. Buy it at parts shop. You must remove the tensioner assembly to replace the rod. I don't think you hurt anything by loosening the 19mm bolt more than a half turn. You are not the first one to strip the threads on one of these rods and you won't be the last.

Remove the 13mm nut and see if the rod indeed has stripped threads. Keep tension on the rod so it doesn't come off the flats on the tensioner. Maybe you have the oddball car with stripped threads on the nut.

Sixto
91 300SE
81 300SD

Sixto-thanks-I will take a look at the nut. Maybe I'll get lucky.

I just worked on mine this past weekend, and I kept this in mind. Since the nut is a hollow tube, I sprayed in some lubricant (with teflon) to avoid galling the threads and stripping it. It might be too late for yours Mike, but there's always next time...

Stripped mine about 2-years ago.

Yes, loosen the 19mm bolt more than 1/2 a turn (I think I did two full turns).

Good luck,
:-) neil
1988 360TE AMG
1993 500E