[ctesla]

Spanky; first, welcome to Automotive Forums..
as far as multiple tensioner breaks, wow.. usually a non-serviceable item;
1 every 80k to maybe 180k; or never...
if bolt is snapping (grade 5 to grade 8, sometimes grade 10-- you are talking 80-91,000; upto 120,000 psi tensile strength!!) it might be tensioner has sprung and is torque-ing and will not budge, only attempt to tighten..
but if it is a 45-80 dollar tensioner also look at belt part number..
you might need tensioner and belt..
many shops carry some common items on shelf, and order in from parts stores the rest.. if the wait for a serp belt was 3 hours from the pep boys on academy, or special order from carquest, as they had to go grab it from the old warehouse off sierra madre; the tech might have rifled the inventory and found a 3" shorter ribbed belt and stretched it onto the tensioner, keeping the spring taught..
it is probably just bad tensioner, look at receipts and see when p/s pump was serviced (if you have from previous owner?) if they itemized what was Removed + Replaced..