Quote Originally Posted by JB_Fraser View Post
... From the pic’s there appears to be a pulley and housing, from the pulley side the inner shaft(part of the pump) has a recess which I assume held a mounting bolt (so the inside is threaded)....
No, the pic from the OP shows the pump as it came off the vehicle, because the pump that's on my Aveo right now looks exactly like the one in the pic, with no bolt occupying that space. With my curiosity level way up, this afternoon I used a mechanic's mirror to look down that recess. The recess is over an inch deep, and it looks like there's possibly something down there that could take a bit. But it just doesn't seem like that could be the head of the bolt that holds this pulley onto the pump. I'm sure this 'bolt' is really mechanically simple, but without seeing it in action it remains a mystery.