Ted's already said what I would have . . . and thought of something that never occurred to me.

The only think I can add is: "think it through!".

By this I mean, look at the pump, and the pieces, and mentally work through all the possible paths water could take, and end up where ever you are seeing it end up. If you build motors, you can almost certainly do the visualization required to do what I'm suggesting. Once you've thought through all the possible paths, go back and look at the pump and pieces again, and check each with the understanding in view of HOW it would have to fail to produce the results you are seeing.

Be particularly careful to make sure you clearly understand how each seal, and especially the pump seal, works . . . then you can understand how it would have to fail to do what it's doing, and THEN you'll know where to look to find the failure.