Your car cooling system is a key element that greatly affects the efficiency of our vehicle. It is made up of different components and uses coolant for a number of purposes: The main purpose is transferring heat and preventing engine damage caused by freezing or boiling. The second purpose is for climate control in the vehicle’s cab during cold ambient temperatures.

It plays an essential role for keeping the engine within operating temperatures, as well as protecting the block thanks to the water pump, which circulates coolant throughout the engine and cooling system.

While most vehicles only have a single water pump, some others have a second water pump that will expedite the process, known by the name of auxiliary electric water pump.

These pumps were first used on diesel vehicles and their initial purpose was to cool the vehicle passenger compartment. And now, auxiliary water pumps are fitted to many modern vehicles, typically located at the rear of the engine.

So let’s get started. This article provides you with all the necessary details you need to know about this type of automotive water pumps.


What does the auxiliary electric water pump do?


As its name indicates, its main function is to support the vehicle’s cooling system, although its use is largely intended for the comfort of the passenger compartment. It also regulates and distribute the temperature with which the heater is turned on. Regardless of what the thermostat is doing, its main function is to circulate coolant through the engine itself when it is cold.

This water pump is based on the integration of a hydraulic system, an electric motor and also an on-board electronic module. What’s more, noted for being silent and high durable. And also, like the electric water pumps, these do not continuously operate. 

Additionally, more auxiliary water pumps can be added to the vehicle. This will depend on the complexity of the cooling system that the vehicle has.

Thanks to the electrification of vehicles, the auxiliary electric water pumps have led to other utilities such as the cooling of batteries in Hybrid and Electric cars, a current trend in the market.


Read more: Discovering the main water pump components


Differences between a primary water pump and an auxiliary water pump


An auxiliary water pump differs from the primary water pump of the vehicle in a number of different ways. First of all, it is an electrically controlled motor, rather than the vast majority of water pumps that get its power from a timing belts or accessories. It also provides coolant through the heater core when the engine is not running or the RPM is low.

The auxiliary water pump is not in continuous operation. The BCM (controlling module) will control and regulate the water pump depending on the information obtained. This information is based on:

  • Coolant temperature
  • Exterior temperatures
  • Interior tempeatures
  • Engine RPM
  • Vehicle speed
  • Fan speed


Common symptoms of a bad or failure auxiliary water pump

On rare occasions, the auxiliary water pump will experience an electrical problem or engine overheating. When a water pump is bad or failing, there are some different signs it comes with. The main reason why these pumps fail is age and wear of the electric motor. If the auxiliary water pump is inoperative, you might notice reduced heater performance at low speeds and at idle, that is: cause specific system temperature inconsistencies.

Common signs include:

  • Temperature management with fluctuating heat
  • The front Windows defrost does not work
  • The heater with no heat at all

Once you notice any of the signs of a bad auxiliary electric water pump, it is recommended to get the problem resolved immediately. In order to anticipate and prevent future problems, it is essential to use a quality product that is the equivalent of the original part.


Dolz, an expert manufacturer of water pumps since 1934


Nowadays, a wide variety of auxiliary water pump options are available on the automotive market. DOLZ is a supplier of high quality auxiliary electric water pumps, strictly equivalent to the original part. In addition, our water pumps are guaranteed for 2 years from the date of purchase or 50,000 km.

Currently our range of auxiliary electric water pumps offers more than 50 references, all of them now available, which allows us to cover the vast majority of the current fleet of vehicles, fully covering the needs and demands of our customers and allows us to continue expanding our range of products.