S-Belt Tensioner Issue

[USMC_DS1]

Started a DIY to replace my water pump today. Got the airbox out and was about to remove my s-belt. Used a 24mm socket to crack right on the tensioner pulley and that's the problem... it did not move over and loosen the play of the s-belt. In fact, it just turns left and/or right w/o moving the pulley at all. Felt behind the pulley and found a nut to tighten from behind but could not get any of my openbox wrenches to fit in that tight space. Need some shorter wrenches to get in there... Looks like a 16mm(someone please confirm) but wondering if anyone else ran into this issue re the t-pulley and if it's just a matter of tightening(is there a proper torque setting) the front and back(nut and screw) or do I need to be mindful of something... BTW, I replaced my s-belt last year. The tensioner worked properly then... so wondering if I may have cracked on it too hard previously and loosen it... hope it's not a stripped issue. Car is an '08 997.1S with 51K miles.

On a side note: I couldn't find my mechanics extending mirror... had to brake into my wife's make-up bag for a small mirror to get back there. You guess it... she came out to check on me and caught me with her "compact" inside the engine compartment. Not a good day for the weekend mechanic.

[USMC_DS1]

As an FYI for others... 16mm bolt on the back of the tensioner pulley can be tighten as you torque the 24mm socket of the tensioner pulley to solve this issue. I used a stubby 16mm open box wrench to accomplish this by wedging it against the tensioner arm. Apply Just enough torque to get it from freely turning on it's own.

[JPA1]

the adage is good advice on the forums never age, and I could not agree more!  I was just going to give up and start ordering the whole pulley kit but you saved my day! I could find  16mm wrench in my toolbox and went back behind the tensioner shaft and here it was! I blocked it and tighten it with the 24mm socket clockwise, and (after almost has lost my hand as the breaker bar slipped,,,) the tensioner pulley started moving as planned and I could take out the old belt,,, New serpentine belt right now, I can go to sleep damned it... ( 1:30 AM in the morning ) :