Did you check this before installing fan?
Fan installation instructions: from dealer website.
It is very important that you test fit and rotate your fan before installing it with the castle nut.
Slide the fan into position on your water pump and rotate the fan by hand to see if the ID of the fan hub is rubbing anywhere.
On a new fan, this will be obvious by the scuffing of the paint. If you feel any drag or rubbing, you will need to file or sand the snout of the water pump wherever the high spot is.
Highspots are caused by irregularities in the casting, castings being bored off center, or castings that are slightly larger in diameter than normal.
Why do you have this problem with a new aluminum fan but not an old steel fan? A casting requires more material thickness than a stamping in the hub area. If these fans were made with the bore as large as a stamped fan, there would be little to no material left to support the edges of the belt pulley.
The result would be the edges of the belt pulley braking off very easily.
Install the key in your water pump shaft and slide the fan into position. You should feel the fan bottom out on the taper of the shaft. If this does not happen, your fan shaft may not have been cut deep enough for the key to set in the proper position.
If you have this problem, first check to be sure the key is seated all the way into the groove of the shaft. If it is in all the way and you still experience this
problem, file the top of the key down slightly so there is no interference when the fan is slid into position.
If the water pump is off of your car, put the fan in position, hold the pump in a vertical position and lightly drop the pump on the impeller end to seat the fan tightly on the taper. It is best to drop it on a firm surface such as an anvil or a concrete floor. Now you can tighten the castle nut and insert the cotter
pin.
Note: The depth of the taper does vary on shafts. If you find that you can not get the nut to go down far enough to get the cotter pin in place, dress the back of your castle nut down with a file or belt sander until the proper depth can be achieved.
