EXAMPLES OF WATER PUMP FAILURE MODES

David Lewis Jan 2014

Failure modes

• Corrosion• Cavitation and Erosion• Electrolysis• Body damage (Cracking)• Dirt or incrustations• Excessive use of gasket sealant• Impeller cracks• Overload (Tension)

Corrosion

CAUSE

Use of Non specified manufacturer coolant

Top up with Water only

RESULT

Rust contaminates the cooling system and results in leakage.

Cavitation and Erosion CAUSE• Incorrect bleeding

of cooling system• Temperature

exceeds boiling point

RESULT• Loss of flow, holes

in casting leading to leakage

Electrolysis

CAUSE• Low PH value causes acidic

action.

• Incorrect coolant

RESULT

• Reduced flow and over heating

Body Damage (Cracking)

CAUSE• Over tightening of bolts• Non sequential tightening of

bolts• Porosity (Unlikely)

RESULT• Unable to fit pump• Pump leaks in service

Dirt or Incrustations

CAUSE• Engine not flushed

out when changing cooling system components

RESULT• Damages the

surface of the mechanical seal.

Excessive use of gasket sealant

CAUSE • Over application

to ensure it fits first time and doesn’t leak

RESULT• Sealant strands

detach and force themselves between the unitised seal

Impeller Cracks

CAUSE• Poor handling of

pumps

RESULT• Loss of interference

between impeller and centre spigot

• Gradual erosion of the impeller

Overload (Tension)

CAUSE• Don’t follow

vehicle manufacturers instruction

• Belief in Automatic tensioners

Result• Bearing failure• Extreme Engine

damage (Particularly in synchronous drive)