Water Pumps The Heart of the Cooling System

Oct. 12, 2010 - PRLog -- The Heart of the Cooling System The water pump is a precision instrument designed to work in a highly stressful environment to keep an automobile’s circulation system cool and functioning correctly. The failure of any basic water pump component can lead to the need for replacement. Varying by model, coolant enters the water pump housing through the radiator outlet. Force from the rotating impeller inside the pump acts as a vacuum and pulls the coolant toward the center of the pump. The coolant fills the shallow cavity where the impeller rotates in either standard or reverse direction, depending upon the model. The impeller disperses the coolant into surrounding outlets that lead to various sub-systems within the cooling system.

Before Installing a New Water Pump • If the old water pump will still circulate coolant through the engine, ALWAYS clean the cooling system with a chemical cleaner and reverse fl ush all sediment, rust, and scale before removing the old pump. Failure to do so can result in premature seal failure in the new pump. • Clean out any built-up sediment and scale from the impeller cavity in the engine block.

TROUBLESHOOTING:

Regular inspection and maintenance of the cooling system should detect early signs of component wear or damage. This general troubleshooting guide deals with the most common and obvious signs of cooling system trouble: overheating and inadequate circulation. For other cooling system related symptoms and more specific analysis, refer to the proper service manual.

Overheating

Coolant Leakage

Loss of coolant is one of the major causes of engine overheating. Coolant leakage allows pressure to bleed out of the system, which lowers the boiling point of the remaining coolant. It also allows air to enter the system, which reduces cooling efficiency by insulating and trapping heat.

Regular inspection of cooling system components can often detect early leakage problems. Therefore, identifying a damaged or worn component before it causes failure or overheating is important. Here are some of the key areas to check for leakage during normal periodic maintenance:

• Radiator core and tanks: Look for

signs of leakage or damage of cooling fins and tubes, plus welded seams.

• Hoses and connections: Check condition of all hoses and inspect

tightness of all clamps.

• Water pump: Carefully check for leaks at the gasket surface and at the water pump weep hole.

If the source of an external leak is not detectable, refer to the proper service manual for procedures to detect internal (engine) leaks.

Inadequate Circulation

If overheating does not appear to have been caused by coolant leakage, the cause may be related to: (1) poor circulation of coolant, or (2) lack of airflow through the radiator. Each cause is discussed below.

Coolant Circulation

Allow the engine to warm up to normal operating temperature. With the engine idling, firmly grasp the upper radiator hose to momentarily restrict its flow. (Be careful, it may be hot!) Slowly relaxing your grip, you should feel a surge of coolant going through the hose. This indicates that the coolant is being properly circulated by the pump and that the thermostat is open. If the hose is warm but the surge is not felt, the pump may not be properly circulating the coolant and the pump may need to be replaced. If the hose remains cold when the engine is fully warmed, the thermostat may be inoperative and should be replaced before the system is retested.

Note: Before performing this test, observe the relationship between the fan and the hose. Some vehicles may be unsafe to test in this manner, because of the proximity of the fan to the upper hose. Never reach around or place hands or clothing close to the turning fan.

Air Flow

With the engine turned off, check the radiator cooling fins for restrictions. Shine a bright light from the fan side of the radiator and observe from the other side. This should reveal any obstructions such as dirt or bugs. Spraying with a hose from the fan side should dislodge these particles. If the radiator fins appear to be clean, the radiator may need to be removed and examined for leaks or internal restrictions by a radiator specialist. The fan clutch can be another cause of poor air circulation, and should also be examined.
Note: On FWD vehicles, the electric fan can be programmed to operate for specified periods under specific operating conditions. For instance, to provide necessary cooling, many fans will continue to run for a short time even after the engine has been turned off. Consult the proper service manual before evaluating electric fan operation.

Water Pump Failures and Causes

Failure Symptom 1 Seal Leakage–Dirty System



Cause of Failure: Cooling System Contamination


The abrasiveness of the particles found in a badly contaminated system will prematurely wear the water pump seal. Harmful contamination is common in systems that are not properly maintained. A system that is not properly pressurized will allow air to enter and promote the buildup of rust. If water with a high mineral content is added to the system and is heated, it will begin to form deposits that will accumulate and cause passage restrictions that may damage the seal.

Remedy

Thoroughly flush a contaminated system BEFORE replacing the water pump. Check system pressure, use correct coolant mixture, and consider using demineralized or distilled water where deemed necessary.

Failure Symptom 2 Shaft Breakage

A clean break indicates an “instantaneous” fracture caused by sudden overload or imbalance.

A break usually occurs through the front bearing race portion of the shaft. Above, this particular break can be noted by a clean fracture, rather than blue heat discoloration, which can appear in this same type of failure.

Cause of Failure:Bearing Overload

A bearing can fail as the result of a sudden overload caused by vibration or imbalance. A lack of heat-related discoloration would indicate it was sudden rather than gradual, and was probably compounded by rapid engine acceleration. Blue discoloration of the shaft would indicate that there was excessive heat buildup for some period prior to shaft breakage. The tremendous forces created by an imbalance would overload the bearing, generating a great deal of heat. Rapid acceleration and high RPM operation would only accelerate bearing deterioration.

Remedy

Carefully check alignment of all pulleys. Also check the pulleys for straightness or fatigue. Install belts using a belt tension gauge, paying attention to the manufacturer’s recommendations. Carefully inspect fan/fan clutch assembly for a bent or damaged fan, a worn spacer, or a worn or damaged fan clutch. Be sure to evenly tighten the mounting bolts to manufacturer’s specifications.

Failure Symptom 3 Casting Breakage

Excessive vibration shattered this casting. Breakage will typically occur around the bearing support.Cause of Failure: Excessive Vibration

Generally speaking, casting failure is associated with heavy vibration or imbalance, which can be caused by a badly worn fan clutch or a bent fan.

Remedy

Carefully inspect the pulley, belt alignment and fan/fan clutch assembly, and replace any bent or worn components.

Failure Symptom 4 Seal Leakage–Clean System

Adding cold coolant to a hot system can crack a ceramic seal.

Leakage was observed from the water pump seal pictured above, which had been installed recently in a clean coolant system.

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