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Signs of a Bad Water Pump

Dan Ferrell writes about DIY car maintenance and repair. He has certifications in Automation and Control Technology and Technical Writing.

Signs of a bad water pump may include:

  • Leaking coolant
  • Poor or no coolant circulation
  • Noisy pump operation
  • Intermittent cooling system issues

If you recognize any of these symptoms, take a look under the hood with the help of the following sections and your vehicle repair manual.

Having the repair manual for your particular vehicle make and model will help you to locate components, diagnose, and, if necessary, replace the water pump in your car.

You can buy, if necessary, a relatively inexpensive copy of your manual through Amazon.

Haynes manuals include:

  • Photographs
  • Parts location
  • Specifications for parts replacement
  • Systems descriptions
  • Troubleshooting guides
  • Electrical diagrams
  • Maintenance schedule

You can save a lot of money just by keeping up with your vehicle maintenance, and avoid unnecessary repairs.

Before you start your diagnostic, make sure you know how the pump runs in your particular model. A water pump may be driven by the camshaft, crankshaft, a belt, or an electric motor. This will help you decide how to go about some of the tests described in this post.

Then, go over the following sections to diagnose your water pump, and use your manual to locate or remove components as necessary.

In This Article

1. What is the Job of the Water Pump
2. Checking for Water Pump Leaks
3. Checking for a Noisy Water Pump
4. VIDEO: Diagnosing a Water Pump and Cooling Fan Assembly
5. Checking for Air Leaks in the Cooling System
6. Checking Water Pump Operation
7. Electric Water Pump Problems
8. What Causes Water Pump Premature Failure?
9. Resources

The water pump moves coolant into the engine.

The water pump moves coolant into the engine.

1. What is the Job of the Water Pump

Basically, the water pump's job is to push coolant from the radiator into the engine.

Usually, a pump will perform well without problems for about 100,000 miles or more before it starts to fail.

When this happens, the water pump will leak coolant or make noises before it stops working.

On vehicles equipped with an electric water pump, though, a typical fault will cause the pump to stop working because of a circuit failure.

Careful With Moving Parts

If you need to work on the engine when it is running, make sure to keep your hands, clothes, and tools away from moving components like belts, fan, and pulleys.

Rust will eat into the water pump seals and cause coolant leaks.

Rust will eat into the water pump seals and cause coolant leaks.

2. Checking for Water Pump Leaks

Water pump leaks are perhaps the most common issue, specially after years of service. However, problems like poor cooling system maintenance or engine overheating may cause the pump to fail prematurely.

  • First, locate the water pump in your vehicle.
    • Depending on your particular model, the pump may be located behind the cooling fan, in front of your vehicle, or under the engine front cover. In this case, you may need to remove the timing belt cover. Consult your vehicle repair manual if necessary.
    • Some vehicle models don't offer easy access to the engine's front cover. In this case, you may want to first check under the cover for signs of leakage.
    • If necessary, raise the front of the vehicle using a floor jack. Make sure to support the vehicle using a jack stand.
    • If you see signs of a possible leak, then it's better to remove the cover for a closer look before this potential failure causes severe damage. You may be dealing with a water pump or head gasket leak.

A water pump leak usually comes from a worn seal or failed bearing. In most cases, you'll be able to see coolant seeping out through the pump's weep hole or the outer seal.

If you suspect the water pump is leaking but need to confirm your diagnostic, you can use a pressure tester tool to check the cooling system. If you don't have this tool, your local autoparts store may loan you one.

Consult your vehicle repair manual for more help on this issue. Also, check the Resources section at the end of this post.

A clean radiator and proper coolant system maintenance prevents premature water pump failure.

A clean radiator and proper coolant system maintenance prevents premature water pump failure.

3. Checking for a Noisy Water Pump

A noisy water pump is another common symptom. Depending on the particular fault, a water pump may produce different type of noises.

Typical Water Pump Noises

NoisePossible Fault

Whining

Failed pulley

Squeaking

Defective bearings

Groaning

Loose belt or bad pulley

Rattling

Bad impeller or shaft

Grinding

Bad bearings

Keep in mind, though, that not all noises you hear under the hood come from a failed water pump, so make sure to listen closely to the water pump using one or more of the following methods. If you are dealing with under-hood noises, you can find more help on this in the Resources section at the end of this post.

Using a stethoscope:

It is a good idea to use a mechanic's stethoscope or a length of hose to check for pump noises. Any of these tools will amplify any noises coming from the water pump.

  1. Set your transmission to Park (automatic) or Neutral (manual).
  2. Engage the emergency brakes.
  3. Pop the hood open.
  4. Start the engine and let it idle.
  5. Put one end of the hose against your ear and the other end at the pump.

Try to listen for a rough sound at the pump.

When using a stethoscope or a hose as a diagnostic tool, make sure to stay away from moving components during your diagnostic.

If the pump is noisy, replace it.

Check the water pump pulley:

On some models, a serpentine belt or drive belt runs the water pump.

Remove the belt and make the following checks:

  • Turn the pump's pulley by hand and check for roughness or looseness.
  • If any of these conditions is present, replace the pump.

Checking a cooling fan-pump assembly:

On models where the cooling fan mounts on the water pump, check the pump bearings manually:

  1. Remove the belt or serpentine belt.
  2. Hold the fan blades with both hands.
  3. Try to move the fan in and out, and up and down.
  4. If you can move the fan more than 1/16 inch (1.58 mm), the pump bearings are worn or have failed.

If necessary, replace the water pump. Consult your vehicle repair manual for more help. Also, check the Resources section at the end of this article. There, you can find more help on replacing a water pump and dealing with under-the-hood noises.

The following video gives you some visual clues you can use when checking a water pump and cooling fan assembly.

4. VIDEO: Diagnosing a Water Pump and Cooling Fan Assembly

A blown head gasket may cause an air leak into the cooling system and affect water pump operation.

A blown head gasket may cause an air leak into the cooling system and affect water pump operation.

5. Checking for Air Leaks in the Cooling System

Air leaks into the cooling system will cause problems for the water pump as well.

Do the following test:

  1. Verify coolant level is correct.
  2. Unplug the overflow tank hose from the radiator.
  3. Connect a hose of the same diameter to the radiator outlet, where the overflow tank connects to.
  4. Using a container of water, submerge the other end of the hose in the water.
  5. Start the engine and let it reach operating temperature.
  6. Ask an assistance to increase engine speed.
  7. If you see a stream of bubbles in the jar, air is leaking into the system.

Usually, an air leak in the cooling system is caused by a blown head gasket. If necessary, do a compression or combustion leak test. Consult your vehicle repair manual.

Check coolant flow to verify water pump operation.

Check coolant flow to verify water pump operation.

6. Checking Water Pump Operation

Although not as common as a leaking or noisy problem, a shaft or impeller failure can occur through wear or excessive corrosion.

Sometimes, checking for a failed shaft or impeller is not as difficult. However, an intermittent cooling problem may be harder to detect.

To check pump operation:

  1. Set your transmission to Park (automatic) or Neutral (manual).
  2. Engage the emergency brakes.
  3. Pop the hood open.
  4. Start the engine, let it idle, and wait for it to warm up.
  5. Ask an assistant to increase engine speed.
  6. Squeeze the upper radiator hose with your hand. You may need to use a piece of cloth if the hose feels too hot.
  7. You should feel a pressure surge as coolant rushes through the hose; otherwise, the water pump is not working.

Another practical way to check for water pump operation is by watching for coolant flow through the radiator neck, if your radiator has one.

  1. With the engine cool, remove the radiator cap.
  2. Start the engine and wait for it to warm up.
  3. As the engine warms up, you'll see coolant starting to circulate through the radiator neck; otherwise, the water pump impeller or shaft is not working.

Even if your water pump passes this test, remember that a worn impeller won't be able to circulate enough coolant to keep with the engine cool enough. Check your water pump's service schedule and replace the pump if necessary, even if it seems to be working fine.

If your electric water pump fails, check the circuit.

If your electric water pump fails, check the circuit.

7. Electric Water Pump Problems

In most cases, a problem with an electric water pump will cause the pump to stop working.

You may be able to troubleshoot the pump's electric circuit.

If necessary, consult your vehicle repair manual.

If your timing belt runs the water pump, replace it as well when installing a new water pump.

If your timing belt runs the water pump, replace it as well when installing a new water pump.

8. What Causes Water Pump Premature Failure?

Several situations may cause a water pump to fail prematurely. However, the most common source of problems is poor cooling system maintenance.

  1. Poor maintenance will cause the water pump to fail prematurely:

    • Lack of sufficient coolant. Failing to top off the cooling system as necessary.
    • Failing to replace coolant at regular intervals.
    • Running the water pump with a worn out belt.

    Air in the system and using water with high mineral content promotes rust growth, accelerates pump seals, shaft, and bearing wear and damage to other system components due to overheating.

    If your problem is corrosion, make sure to flush the system before removing and replacing the old water pump.

  2. Using the wrong antifreeze for your application.

    Always check your vehicle repair manual for the recommended antifreeze for your particular make and model, and replace it on schedule.

  3. On chain-driven water pumps, a common cause of failure comes from:
    • Worn tensioner or guides
    • Lack of frequent oil changes (on water-pump tensioners run by oil pressure)
  4. Cooling fan problems:
    • A bent fan
    • Fan blades with a missing piece
    • Cracks on a fan blade
    • Faulty or worn fan clutch
  5. Other related issues that cause trouble for the water pump.
    • An over-tightened belt will lead to pump bearings overheat and failure.
    • Rust in the cooling system will cause seal, shaft and bearing premature wear.

9. Resources

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2022 Dan Ferrell