What You Should Know About Your Car's Water Pump

What is a Car Water Pump?

Also known as the coolant pump, a car water pump is a belt-driven machine that maintains the circulation and regulation of the coolant from the radiator to the engine. Depending on the car model, the drive belt could be a fan, serpentine or timing. 

A timing chain can also be used in place of the belt. However, with a timing chain, the water used for cooling can end up mixing with the oil once the pump fails and cause the engine bearings to fail.

As you can tell from the name, the coolant, in this case, is water. The exterior of the water pump of various cars may differ from each other. The interior parts, however, perform the same function and thus will be similar in construction.

The water pump is positioned just behind the fan belt. In some cars, it is located on the front, while in others, it is on the side. 

It takes a disc shape at the centre, with arm-like components radiating outwards. Of these arms, one is connected to the radiator while another attaches to the engine. Once a car pump malfunctions, both engine and car will overheat, which in turn may lead to many other problems.

Parts of a Water Pump

The car water pump consists of different components. The main ones include bearings, body (housing), gasket, impeller, and seals. 


It refers to the shell encasing the pump and is typically made from iron or cast aluminium. Nowadays, stamped-steel is also used.

Weep Hole

The weep hole is located in the housing of the pump. It is a small part, but it has an important role. It ensures that the leaking coolant escapes instead of being trapped. If trapped within the pump, the leaking coolant will affect other components.


Unlike the housing, which is made from metallic elements, the impeller can be made from metal or plastic. It ensures the perfect distribution of the coolant. The rate at which the impeller distributes the coolant is dependent on the engine’s RPM.


As the name suggests, it ensures that the coolant cannot enter the bearing assembly. Coolant leakage is mostly due to seal failure. These leaks can cause the water pump to fail.


The bearing assembly supports the shaft to help it achieve a continuous, controlled, and stable rotation. 

Hub or Pulley

The hub or pulley is connected at the top of the shaft. It ensures that the pump has enough power to rotate the impeller and drive the coolant through the engine. 

Hybrid cars are fitted with electric water pumps that are driven by electric motors housed within the pump’s body. 

How Does It Work?

The car’s water pump operates by applying the concept of centrifugal force. When the engine runs, the fan belt turns. The turning fan belt will then cause the axle and the connected vanes to rotate. This rotating motion creates a suction force, which pulls water from the radiator.

The massive power generated by the vanes forces the water against the exterior walls of the pump, pushing it to the engine block and the cylinder head. 

From the cylinder head, water then flows back into the radiator. The cycle starts again and repeats this process over and over as long as the engine keeps on running. The thermostat ensures that the amount of water flowing through the system is enough to cool the engine.

The car coolant pump can move over 7,000 gallons of the coolant in an hour. At peak RPM, the pump can recirculate the coolant over 20 times in a minute. The circulation rate depends on the speed of the engine. If the engine speed is slow, the pump will also work at a lower circulation rate.

When the engine speed increases, more heat will be generated. As the new conditions require more cooling, the impeller will operate at higher speeds.

Signs That Your Water Pump is About to Fail

Just like any other car component, the gasket wears out and erodes as the water pump keeps running. 

Erosion of the gasket makes the water leak out of the hole. Leaking should be your warning sign that the water pump is failing. If this happens, you should head to the auto repair shop immediately.

A failing pump will cause overheating of the engine and, eventually, engine breakdown. For this reason, it is crucial to inspect the whole car cooling system. This routine task entails examining leaks and loose bearings and testing of coolant condition and belt tension. 

Use a high-quality flashlight to inspect leaks in case the water pump's position is visible. While at it, you should check whether the weep hole has any wet or dry coolant residue. Also, check for any leaks in the gasket and the timing cover area.

When replacing a water pump that has failed because of loose bearing, check the fan for any damage and make sure that the tension on the belt is constant. 

Finally, test the temperature protection and pH levels of the coolant, its flow as well as pressure. The coolant’s pH should be maintained in the range of 8.5 to 11 to prevent corrosion. 

The water pump does a great deal of work to ensure that the engine runs well. Before embarking on long road trips, have a certified technician thoroughly inspect your car's water pump.

(Blog from carpart.com.au)

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