Removed the waterpump on my '92 300SE to replace a leaking pump-to-block o-ring. Doing so of course requires releasing the tension on the belt. Also replaced a rattling tensioner shock absorber while I was at it.

Went to reassemble and retension everything and couldn't for the life of me figure out how to set the tension. AllData diagrams indicated I should align the arrow on the tensioner housing with some seemingly non-existent fixed pointer.

I checked another source for info - the CD I got from MB for the car and it has an exploded diagram of the tensioner device that shows a pointer that goes in between the outer bracket and the tensioner body.

The PO said he had recently replaced the tensioner and the part does look new.

My question is - without that missing pointer, how do I go about setting the tension on the belt. I know that if it slips it's too loose - but over tightening it just ruins bearings in all sorts of expensive items like A/C compressors, etc.

Any suggestions?