the cone is a piece of metal (about 2" diameter with a hole in the middle) that sits in front of the impeller. when you take the front half of the pump off, you're staring at the cone if you look into the rear half of the pump housing (still on car). it is held in place with punches in the aluminum of the rear pump housing. the two metals are dissimilar, so my thought is that the different expansion/contraction rates are what causes the problem with the cone coming loose. mine was loose, luckily no overheating or broken impeller...i had ford put a new one in under warranty.
EDIT:
damnit terry beat me to it.
