sounds like you have a case of a previously repaired tensioner bracket.
this is a metric bolt. with and without the shock absorber.
if its 1/2" its been stripped out.
@
FarmerFrank just had the same issue.
Best fix I found for this is to rip all that junk off and go to V belts.
Serpentine (and stupidity) cost me an engine.
Too many different tensioners and belts to have the "correct set up". Had the old belt pop off 3 times, the third time it took out my cooling lines as I was about 1.5 miles from home. I knew the belt popped off but not the lines. I was pissed at several other things that day and kept driving. Made it almost to the house when the truck stopped moving, I then realized what else had happened.
Fast forward a week later. I put on a new belt after a few failed attempts of finding the correct one. All the truck ones were too short. I think I ordered one for a van and it fit nice and snug with good tension.
About 10 pm on a Friday night I needed fuel for the combine. Went home, put tank on truck and headed to the pumps. I made it 3 miles when the new belt SHREDDED into a 100 chunks. Again, I was tired, stressed, and upset so I spun around and drove back uphill home. When I pulled in my driveway it was steaming like crazy. I cracked a beer and watched in disgust.
Next day I tore all that stuff off and installed V belts and a new starter since the old one was weak. Every once in a while when I tried to start it after that it would just stop cranking. Hydro locked. Pulled plugs and had a water fountain. Factory turbo engine with cracked heads.
It's now a IDIT dust collector and I have a 94 factory turbo truck with a 87 studded 6.9, v belts and a turbo. All thanks to serpentine belts.
Rant over. Thanks IdIot for bringing back great memories.