Water pump hex input shaft breaking

[samgrylls]

Hey guys,

A few months ago my water pump failed, and when I pulled it off the car, I noticed that the socket where the hex shaft inputs had broken into a bunch of pieces. I replaced it, and the new pump only made it ~200 miles before failing in the exact same way. The new pump was a Meyle aftermarket one - not sure if the old one was aftermarket or OEM. Is this a known problem with these pumps? Is it just crazy bad luck, or could there be something else going on that's causing them to fail?

One thing I was thinking is that maybe I'm missing an O ring. Is there supposed to be an O ring around the metal part where the hex shaft input is? Like around the larger diameter aluminum part, so it'd be sandwiched against the block?

Thanks,
Sam