I cut it down to 12.4mm and still can't get it to fit. Can you grind the socket down to a smaller O.D. up by the end that receives the extension? The closer to the top, the smaller the diameter. Someone in this thread mentioned that those bolts don’t require much torque so you may be able to remove...

Point well taken there. Of course we’re assuming that the person who is reassembling it will be able to torque that little bugger exactly right anyway? Mmmm, maybe.....

Another crazy idea I’ve considered for that pesky bolt..... The manifold flange is about 1/2” thick where the bolts go through it. What if you ground off 1/8” or 3/16” of material in the area of that bolt and then used a bolt that’s that much shorter. It would provide 1/8” or 3/16” additional cleara...

Consider replacing that bolt with a torx head bolt. It might make it easier on the next person that has to loosen it.

Have you done any recent work on one of the axles such it might not be fully connected at the splines? (Long shot, I know.)

“...Are you saying take it somewhere else after I replace everything?...” Oh, no, that’s not what I meant. I’m not real familiar with the inspection process in your state. But your original post sort of sounded like the same shop that does the inspection also does the repairs. Maybe I have that wron...

Is it wise to have the inspection performed at a shop that can profit from the outcome of that inspection?

When you had the serpentine belt off did you spin the tensioner pulley and listen to it? With the engine idling, a well placed (CAREFULLY placed) stethoscope or long screwdriver held to your ear can often zero in on a component with a bad bearing. You could also run the engine briefly with the serp ...

Try a wrecking yard.

Odd that the problem only arises after driving for 40 minutes. That would suggest it may be heat related. Have you flushed the fluid recently? Volvo recommends the Pentosin type fluid. Also, is there any chance the serp belt is slipping in the pump
pulley when it gets warm?