According to the experts at Haldex, broken water pump bearings or shafts are caused by one or more of the following conditions:
Excessive engine acceleration: If this occurs, particularly in low gear during quick getaways, it places heavy overloads on the bearing. So do high speeds, where severe whipping can cause fractures.
Defective fan: Minor fan defects can strain the water pump shaft. A small piece of fan blade missing, fatigue cracks near the rivets or bent fan blades can cause serious load problems.
Fan not square with shaft: If it is not square, the fan will wobble, causing vibrations. If shaft spacers are used, improperly torqued mounting bolts will cause the fan to be tilted and may permanently deform the spacer.
Bent or cracked pulleys: This usually happens when a pulley is improperly handled or installed.
Fan belt too tight: An overtightened fan belt can overload the bearing. It also causes bending of the shaft.
Shaft failure caused by imbalance: Discoloration around the fracture indicates unusually high temperatures caused by centrifugal forces due to imbalance. Lack of discoloration at the break indicates no heat buildup occurred before a sudden vibratory overload of the shaft caused a clean, instantaneous fracture.
To prevent water pump failure:
• Always tighten fan belts properly.
• Never hammer or even tap the bearing shaft when aligning the pump during installation.
• Seat fan square with pump shaft.
• Always replace damaged fans. Never straighten bent blades; replace the complete fan. If a fan breaks, it can cause serious personal injuries and vehicle damage.
