Causes of Water Pump Failures

Contamination

If coolant is contaminated, the outside of the pump will show signs of it. Look for rusty coolant seeping out of the weep hole. There will be deposit build-up of calcium and rust if the condition has gone undetected for along period. Particles of this contamination will destroy the water pump seal.

Radiator Cap

Modern radiator caps are actually pressure valves that Inspect the radiator cap. If the system is not properly pressurized, any air that gets in accelerates the rust problem.

Coolant Radiator Cap

Use distilled water. Tap water usually contains minerals that, when heated, percolate out and form deposits that block cooling system passages. Before installing a new water pump, thoroughly flush the cooling system and replace coolant with the manufacturers specified mixture and fluid level.

Broken Shaft

A clean fracture through the front bearing race part of the shaft means the pump was subjected to a sudden overload or imbalance caused by vibration. Rapid acceleration can also play a part. If the broken shaft is discolored (usually blue), the dam-age was gradual, indicating excessive heat build-up before the shaft broke. Again, imbalance is the cause, amplified by rapid acceleration and high rpms.

Check the condition of the pulleys and especially look for pulley misalignment. It may be the belt is improperly tensioned or the automatic tensioner is defective. Use a tension gauge to verify. If equipped with a water pump mounted fan, inspect the fan/fan clutch assembly. The fan may not be squarely mounted on the shaft. A bent or damaged fan, a worn spacer, or a worn or damaged fan clutch could also be factors contributing to the break.

Broken Housing

Any break in the casting normally happens around the bearing support. It’s caused by heavy vibration or imbalance which, in turn, is caused by a worn fan clutch or bent fan.

Defective Fan Clutch – Look for three things:

If there are oil streaks and dirt on the fan clutch, the internal clutch fluid is leaking.Next, check the condition of the bearing. With the engine off, grasp the fan blade on either end and check for lateral movement. There should be no more than _”of side-to-side movement. If the fan blade moves more than that, the bearing is worn out and the unit needs to be replaced.

Third, run engine until it reaches operating temperature. Turn engine off and gently spin the fan blade. If it spins more than twice, the clutch is worn out. If the fan is noisy – or if the fan won’t turn at all – the unit is worn out and needs to be replaced.

Weep Hole Seepage

When a pump is new, some seepage from the weep hole is normal. It takes a few hours of operation for the seal to properly seat itself. However, any weeping after this break-in period means the seal is damaged and on its way to failure. A failed seal allows coolant to leak through the bearings and wash away the lubricatant.

NOTE: The seal face or mating ring can be cracked when installing a new water pump if engine is started before adding coolant.

Coolant degradation

Contaminated or deteriorated coolant will cause corrosion of the water pump components. This condition is due to poor flushing of the radiator, lack of regular replacement or reuse of old coolant. This will lead to engine overheating. Reusing or using degraded coolant will corrode the body, impeller and mechanical seals of the water pump and failure of other cooling system components, Use a premium grade coolant. It contains everything your engine needs. Adding additional lubricants does not improve pump performance.

Excess torque of the mounting bolts

Excessive torque applied to any mounting bolt can cause the threads to be stripped in the casting or mounting surface. If the correct torque is not evenly and correctly applied, casting breakage will occur. Be sure the mounting service is clean to avoid contamination. Tighten mounting bolts in a diagonal (star) pattern and apply torque specified by the vehicle manufacturer.

Excessive use of sealant

Sealant can interfere with the mechanical seal causing leaks. Deterioration of the sealing performance is caused by unevenly applied sealant (RTV), use of adhesives and sealants used on O-rings causing deterioration of the elasticity of the rubber. Do not use sealants