2005 Pontiac Vibe.
Silly mistake–I replaced a belt tensioner due to excessive vibration in the top part where it attaches to the engine. Whether the movement weakened the stud bolt first or I just used too much force – likely both but definitely the latter – it snapped off. It is the 12mm bolt not the big 17mm that goes through the belt tensioner.
I am having trouble finding a diagram online to identify if a) the stud bold is double threaded, which I assume it is, and if so b) would some vice grips + penetration fluid be enough to remove it possibly?
My other ideas were to use some metal/metal epoxy to fasten the threads to the new belt tensioner and then find a mechanic to tack weld it as well… If it helps, the belt tensioner sits flush with the broken bit of the stud bolt.
ps. edited for a bit of clarity and to remove imgur/outside links.
pss. very happy i did not go the expoy route before trying the obvious first steps.