The water pump is a vital part of your vehicle's cooling system. If it develops a leak around the shaft, or the hub wobbles and is loose or noisy, it should be replaced. Likewise, the fan clutch should be replaced if there is a fluid leak, noise or roughness when turned by hand, the unit won't turn, or the leading edge of the fan moves more than 1/4" from front to rear.
 

Generally, the water pump is located on the front of the engine. A drive pulley is mounted on the pump hub, and the fan is attached to the pulley. The fan clutch, if used, mounts to the pulley with bolts through the flange. The fan mounts on the back side of the clutch with separate bolts or studs.