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Water Pumps: What You Need to Know

202401 what you should know about water pumps scaled jpg Water pump | illustration by Paul Dolan

Your car’s water pump circulates coolant throughout the engine, where it soaks up heat, and into the radiator, where the coolant is cooled and then recirculated back to the engine to start the process over again. (Because of this, the water pump is sometimes more appropriately called the “coolant pump,” as coolant is a mixture of water and antifreeze.) If the water pump fails to circulate coolant, the engine will typically overheat in very short order. So, what things can cause a water pump to fail, and when should you think about replacing it?

Related: What Is Coolant and Is It the Same as Antifreeze?

What Can Cause the Water Pump to Fail?

Sometimes, it’s not the pump itself that fails; it’s what drives the pump. While most automotive water pumps are driven by the engine through a belt, in some cars — especially hybrids — the water pump is driven by an electric motor.

In the case of a belt-driven water pump (which is found in most cars on the road today), the pump will stop working if the belt driving it breaks. That’s normally the accessory drive belt, which you can typically see on the outside of the engine (it’s often called a serpentine belt because of how it winds its way around the pulleys of the components it drives). In some cases, however, the pump may be driven by the engine’s timing belt or chain, which is on the inside of the engine.

If the pump is driven by the serpentine belt and the belt breaks, you’ll usually get a “heads up” because the battery light should illuminate on the instrument panel or the steering wheel will become hard to turn. That’s because the serpentine belt also typically drives the alternator that recharges the battery and, in some cases, the power-steering pump.

If the battery light illuminates, pull the car over as soon as possible and check to see if the serpentine belt is still in place. (The battery light may also come on because the alternator has gone bad, but that’s not likely to cause an immediate problem; overheating may.)

In some cars, the power-steering pump is also driven by the serpentine belt, and the steering wheel will become hard to turn if the belt breaks. However, many newer cars have electric power steering, in which case the “hard steering” warning won’t materialize. If you keep driving, the next indicator will probably be the temperature light going on.

If the water pump is driven by the internal timing belt or chain and the belt or chain breaks, you don’t have to worry about the engine overheating because the engine will quit running immediately.

Whether the water pump is driven by a belt or an electric motor (which can also fail), the pump itself can have problems. These issues often start as a coolant leak or a screeching noise, so either would warrant taking the car to a mechanic to get it checked out. Your engine overheating is another indication that the pump might be bad.

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When Should the Water Pump be Replaced?

Although a water pump contains wearing components such as seals and bearings, as well as a fanlike impeller that can fail, it usually isn’t replaced simply as a maintenance item since it’s not uncommon for a water pump to last at least 100,000 miles. You can help extend the pump’s life by replacing the coolant at manufacturer-recommended intervals as the coolant contains additives that help lubricate the pump and prevent corrosion, and those additives “wear out” over time.

However, if the water pump is driven by the internal timing belt or chain, it’s often recommended to replace the water pump when you replace the belt or chain as it’s going to wear out eventually. That’s because so much of the repair cost is due to the amount of labor, and the mechanic often has to remove the water pump anyway.

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