The water pump, or coolant pump, is an integral part of a vehicle’s cooling system. Its job is to circulate coolant through the engine and to all the parts of the cooling system.
Without a functioning water pump, the vehicle will be unable to take the excess heat produced in the engine and transfer it to the radiator via the coolant. This means that the engine will start to accumulate too much heat, which will lead to overheating, which can cause major damage to the internal components.The water pump is usually driven by the serpentine belt but may also be driven by the timing chain or belt inside the front cover of the engine. Because of this, the water pump can be affected by other failures like a seized alternator bearing or a broken serpentine belt. A failing water pump can also damage whatever belt that drives it.
Related Article: Serpentine Belt Replacement
What are the Symptoms of a Failed Water Pump?
Signs of a failing water pump can be: higher engine temperatures, a low coolant warning, unusual engine noise or squealing belts, or steam rising from the engine compartment.
When a water pump wears out, it may start to leak. This can be because the seal between the water pump and the block has worn down or because the bearing on the water pump fins wears out and blows out the seal around it.
Because the water pump holds the coolant in the engine under pressure, it’s important that any leaks there be addressed as soon as possible. A very minor leak might be topped off and nursed along, but minor leaks usually mean that the bearings on the water pump are failing, and that can get worse suddenly. It’s usually possible to confirm a failure there with a mechanic’s stethoscope, if leaks aren’t obvious.
When the bearings begin to fail on a water pump, that can also cause the pulley to sit crooked. That can cause a belt to squeal, or in the worst case, it can damage the belt or cause it to fall off the pulleys. In that case, all the other accessories (such as the alternator and power steering) and the belt drives no longer work. If the water pump is driven by the timing belt, then it can damage that belt, which in an interference engine can lead to valve damage. That’s the reason that a new timing belt is usually recommended with a new pump, or that a new pump would be installed with a new timing belt.
The most difficult to diagnose failure of a water pump is when the pump fins wear off of the pump drive and the pump is unable to circulate the coolant through the system adequately. It’s sometimes necessary to remove the water pump to inspect it to confirm this kind of failure, and usually this doesn’t get done before other things (such as the thermostat) are tried. Worn pump fins can lead to elevated engine temperatures and possibly engine overheating. If not addressed, that can cause internal engine damage, including head gasket failure, damage to pistons and valves, or cracks in the block or head.
What Does It Cost to Replace a Water Pump?
The average cost of a water pump replacement is about $500. But as water pumps can be built in many different ways and be located in different places on the engine, the costs can vary from vehicle to vehicle; some are easy to replace, some are very difficult. Here are a few different examples of water pump replacement costs to give you an idea of the range of prices, using $150 an hour as a shop labor rate.
| Car Model | Labor Time & Cost | Aftermarket Water Pump Part Cost | Factory Water Pump Part Cost |
|---|---|---|---|
| 2010 Toyota Corolla, w/2.4 liter engine | $345 (2.3 hrs) | $80, for a Gates pump | $154 |
| 2014 Ford F-150 w/5.0 liter engine | $255 (1.7 hrs) | $140, for a Dayco pump | $145 |
| 2006 Subaru Forester w/2.5 liter engine | $450 (3 hrs) | $120, for an Aisin pump | $170 |
| 2001 Chrysler Sebring w/2.7 liter engine | $990 (6.6 hrs) | $100, for an Airtex pump | $160 |
Added to the costs above would be coolant, where usually at least a gallon is required. A diagnosis is sometimes required as well. In the above examples, the Toyota and the Ford would be fairly straightforward and visible if the water pump was leaking, but on the Subaru and the Chrysler, the pumps are inside the timing cover. Sometimes it’s necessary to pressure test a system to locate a leak, and sometimes a little disassembly is needed to be sure. An hour of diagnosis might be added.
On the Subaru and the Chrysler, the water pump is driven by the timing belt, and typically a new belt would be installed with a new water pump. The labor times do account for that. Sometimes a coolant flush is added, but that’s usually not necessary. The job itself inevitably replaces most of the coolant.
It’s very common to have the thermostat replaced along with the water pump, as it’s a pretty vital piece of the system that’s relatively cheap and easy to replace. The thermostat can also be damaged easily by overheating or fluid contamination, so it’s a common recommendation.
Related Article: Thermostat Replacement Cost Guide
How Can Water Pump Repairs be Avoided?
One of the primary causes of water pump failure is a coolant that is old or contaminated. Most vehicles have their coolant serviced on a regular schedule, which will be detailed in the maintenance section of the owner’s manual. A common interval is every 5 years, or 50,000 miles.
Related Article: Coolant Flush Service
Once a year or so, coolant should be tested regularly for strength using a hydrometer, which should read below -30 degrees Fahrenheit to be the correct mixture. If it fails the concentration test, the cooling system can be drained and refilled with the proper mixture of coolant. This is often done in the fall as part of a “winterization” safety check.
If an inspection of the coolant shows flakes or any rust coloring in the reservoir, the cooling system should be flushed with distilled water to clean out the buildups in the cooling system and then, filled with the proper mixture of coolant and water to achieve the correct strength.
FAQ
In most cases, it’s a fairly challenging job that requires special tools. There are a few engines where it’s not too hard, but most often it’s best left to a shop.
Ideally, as little as possible. But if it’s only a minor leak and the belts aren’t causing an issue, and if there is a temperature gauge that can be monitored, it can be safe to carefully drive a vehicle with a coolant leak for a short time, if necessary. Keeping in mind that overheating can cause expensive engine damage.
No. This is something almost all mechanics are in agreement on; leak-stopping coolant additives generally do a lot more harm than good. They can plug radiators and heater cores and generally cause very expensive damage. While very seldom slowing down actual leaks.