New Aluminum fan, play in shaft

[stickshift]

I pulled the water pump and removed the time bomb two blade fan. Installed the new aluminum fan without any issues, reinstalled pump and was admiring how well balanced and perfectly in-line the blades are. Then, I noticed the shaft moving in and out. I shut off the engine and moved by hand in/out about 1/8 to 3/16 inch. I didn't notice this before with the old fan, but then I wasn't really looking either. My question is: could something have come loose while the water pump was out? I didn't really look to see how the impeller was mounted to the shaft, but I did see a collar with a set-screw on the fan side of the shaft. I checked to see if it was tight and it was. Before I tear it apart again, it this kind of play acceptable? There is no wobble or side to side play.