I am not a mechically inclined person, however, I manage survey crews, therefore, I manage the vechicles they drive. I'm learning, very slowly. My fleet is all F-150 4x4's supercab, triton V8's. Oldest is a '97, newest is a '99, the rest are inbetween. Just replaced a master clyinder and an ABS valve (ouch) that ate up my budget for that one all by itself. It was the newest and the first of the fleet. I'm confused. Why does a ABS valve go bad?