What Causes a Water Pump to Leak? Plus FAQs

The water pump is one of the key components of the cooling system. It recirculates coolant from the radiator and the engine and vice versa. Like any other car part, the water pump isn’t exempted from developing issues or getting damaged.

Water Pump Issues Explained

There are two reasons why a water pump can fail: a leaking shaft seal and a damaged impeller.

Leaking Shaft Seal

A worn shaft seal is the most common reason behind a leaking water pump.

The shaft seal acts as a barrier against rust, sediment, and other contaminants that can infiltrate the water pump housing’s bearing. It also prevents coolant from leaking past the bearing and out of the weep hole.

A worn shaft seal will let coolant leak from the water pump bearing assembly and result in bearing damage.

Because the shaft and bearings are under constant load from the drive belt, timing belt, and cooling fan, they’re expected to wear out after some time.

The pump bearing can fail prematurely due to excessive force if the drive belt is too tight. A fan that’s bent or out of balance can also result in accelerated bearing wear.

Impeller Damage

An impeller is a rotating component that helps increase a fluid’s pressure and flow rate. As the water pump pulls in coolant towards the center of the impeller, centrifugal force directs the coolant outward for the impeller tips to discharge.

Over time, corrosion and metal fatigue can affect the impeller’s operation. For vehicles that have plastic impellers, contaminated coolant can lead to premature wear.

A damaged impeller won’t necessarily cause the water pump to leak. However, it can prevent proper coolant circulation and negatively impact the engine’s operating temperature.

Consequences of Driving with a Leaking Water Pump

An overheating engine is every driver’s worst nightmare. In most cases, drivers won’t notice this problem until the temperature warning light pops up on the dash.

Stop driving as soon as the engine overheats. Ignoring this issue can result in severe engine damage and a very expensive repair bill.

If the engine has overheated, make sure to inspect the entire cooling system and check for leaks. A damaged water pump shaft or vent hole will need to be replaced.

Aside from a leaking water pump, there are other reasons why an engine can overheat. Here are the most common ones:

• Plugged, dirty, or blocked radiator
• Defective fan clutch or electric fan
• Incorrect ignition timing
• Low engine oil level
• Broken fan drive belt
• Broken or damaged water pump belt
• Defective radiator cap
• Dragging brakes
• Frozen coolant (in freezing weather)
• Defective thermostat
• Blocked cooling passages in the engine block or cylinder head(s)

Precautions When Dealing With an Overheated Engine

An illuminated coolant temperature warning light is the first indicator that the engine has overheated. Once this happens, shut off the air conditioning, turn on the heater to full hot, and set the blower speed to high. This will help dissipate extra heat from the engine.

It’s also important to wait for the engine to cool down before removing the radiator cap.

How Much Will a New Water Pump Cost?

The cost of a new water pump can range anywhere from $100 to $500 on parts alone, depending on factors like the brand, assembly inclusions, and your vehicle’s specifications (year, make, and model).

Some water pumps can even take as long as 15 hours to install, which means you’ll be paying a lot more than $500.

Will a Faulty Water Pump Leak When the Engine Is Off?

In some vehicles, the water pump will stop leaking once the engine cools down and will start leaking again once the engine reaches its operating temperature.

Intermittent leaks are often a sign of water pump wear and seal failure. Make sure to have a trained professional inspect your vehicle as soon as you notice signs of intermittent coolant leaks.

How Long Does It Take to Install a Water Pump?

A water pump replacement can take a couple of hours, but this timeframe can vary depending on the vehicle and the pump’s location.

The Basics of Water Pump Replacement

Replacing a damaged water pump requires a specific set of auto repair skills and know-how. If you haven’t had any experience in dealing with this kind of issue before, it’s best to leave the job to the pros.

Having a certified mechanic perform the necessary procedures ensures that all steps for diagnosis and repair are followed correctly. Dealing with a water pump replacement without the right skills and equipment might result in complications with other engine parts.

But if you’re someone who’s had some experience in dealing with car troubles before, here’s a list of what installing a new water pump usually involves:

• Make sure that the engine is cold before draining the radiator. Depending on your vehicle, you can either open the petcock valve at the bottom or loosen the lower radiator hose.
• After draining the radiator, remove the fan belt or loosen the tension on the automatic tensioner (if your vehicle has a serpentine belt drive).
• Remove the fan, fan shroud, timing belt cover, and other components that are blocking the water pump.
• If the water pump is timing chain-driven, remove the accessories from the engine, and proceed with removing the timing cover, timing chain system, and the water pump.
• Unbolt the old water pump and clean the mounting surface.
• Use a sealer or adhesive to mount the gasket onto the new water pump, and bolt the pump to the engine.
• Refill the cooling system.

You can also check out this video for tips on how to replace your water pump:

How Long Will a Water Pump Last?

A water pump should last anywhere between 60,000 and 100,000 miles for most modern vehicles.

Wrapping Up

The water pump is a wear-and-tear component that can develop leaks because of a worn-out shaft seal. Once this happens, your vehicle can overheat and result in severe engine damage if left unaddressed for too long.

It’s also possible for a vehicle to leak coolant from the water pump intermittently. Although it might not sound like a major problem, intermittent coolant leaks are preemptive of bearing damage and worn seals.

Lastly, a water pump replacement is a DIY-friendly task that you can do in your own garage, but only if you have enough knowledge and skills on the topic. Otherwise, the job is best left in the hands of a skilled mechanic.