If the garage that did the pump took the front engine (timing) cover off during pump replacement,
They may have left off a triangular shaped gasket that goes between cover & block.
The idler pulley (that fan hub is on) then sits off square & does as you describe.
Seen some other numpty garage do it
,can be rectified by packing idler with a couple of washers under two rightmost bolts (to make up difference of missing gasket).
Really should be done properly (cover back off) as this gasket also seals water outlet from head.
Seen a damaged,hit in accident idler do same when fan has crushed mounting bracket out of shape.
(not so likely if ok prior pump repair)