Bad water pump symptoms
When it comes to critical engine components, the water pump has to be one of the most important. It is often forgotten, and generally works away under the radar, until it fails.
Recognising the signs of a failing water pump can save you a lot of money in repair costs if it is changed before it fails completely.
The symptoms of a bad or failing water pump include engine overheating, coolant leakage, steam coming from the engine bay, a grinding noise coming from the engine and dried coolant build up around the water pump.
Most water pumps these days last 100,000 miles or more. If you regularly flush the coolant and ensure the auxiliary and timing belts are changed on time, then it's not unusual for the water pump to last the lifetime of the car.
Symptoms of a bad water pump
Water pumps tend to fail slowly over hundreds or even thousands of miles. They generally start to show symptoms of failure long before they actually give up completely.
If you know what to watch out for, you should be able to spot a bad water pump signs before the water pump fails completely.
If your car has a timing belt fitted, then the water pump is usually driven directly by the timing belt. On cars fitted with timing chains, the belt is more commonly driven by an auxiliary belt, that may also drive the air conditioning compressor and alternator.
Either way, the water pump is not usually that easy to access, and can be hidden away behind hoses and belts.
When it comes to assessing the condition of a water pump, you need to take into account the age of the car, the service history and the state of the coolant system. If the coolant and drive belts have not been changed in years, then this is going to adversely affect the condition of the water pump.
Ultimately, the only way to absolutely check for a bad water pump, is to remove it from the vehicle. Before you start draining the coolant system and taking apart the engine, there are some common signs of a bad water pump.
1. Coolant or oil leakage
A common sign of a failing water pump is fluid loss from the coolant system or oil leaking from the water pump. Water pumps have a built in safety feature that can sometimes warn you of impending failure of the water pump before it happens.
The weep hole is a small, unplugged hole on the water pump that allows coolant or oil to escape from the inside of the water pump when one of the internal seals has failed. If oil is dripping from the hole, then the internal oil seal is failing. Coolant or water dripping from the weep hole means the internal water pump seal is worn out.
Fluid dripping from the weep hole usually only occurs when the engine is running and the internal water pump impeller is rotating. If you notice coolant is leaking overnight of after you park the vehicle, this can point to a leak from somewhere else in the system
Sometimes, a there may be a large amount of coolant leaking from the water pump. This can be caused by a failed water pump sealing gasket. This is the gasket between the water pump and the engine block. It doesn't usually fail catastrophically, but it can start to leak slowly, especially on older vehicles.
2. Noisy water pump when running
Bad water pump noises include grinding, squeaking and squealing noises from the engine bay. They can also be caused by a problem with drive belts, pulleys or tensioners.
Bad water pump sounds can be caused by worn shaft bearings or wear to the internal impeller blades. This can happen as the water pump ages, or may be caused by lack of proper servicing.
If the internal shaft bearings start to wear, this will affect the belt pulley and how it rotates. If pulley makes a whining or grinding noise as it rotates, then this points to a worn out water pump that could fail at any time.
Sometimes the noise can be caused by the rotation of the pump impeller blades inside of the water pump. If the blades have become damaged, rusty or clogged with dirt from the coolant, this can cause a noise and can mean that the water pump is ready to fail.
3. Build up of dried coolant around the pump
As mentioned above, sometimes a water pump will leak from around the mounting surface. This is caused by an improperly mounted water pump, or a failing gasket seal.
Most of the time the leak won't be very big to begin with. Instead it will appear as small spots of dried out coolant that look white or chalky in appearance. Over time, this can progress to a larger coolant leak or a rusty coating on the water pump. If a large amount of coolant is leaking from the water pump, then this can point to failure of the mounting gasket.
Not all water pumps use a gasket. Some are sealed using a wet sealant that dries and hardens after installation when it is heated by heat from the engine block. If the wrong sealant, or wrong amount of sealant is used, this can cause it to fail more quickly, or not to seal at all.
4. Over heating engine
An over heating engine is one of the most common symptoms of water pump failure.
If your engine is overheating regularly, this can be a sign that the water pump is not working as efficiently as it should. If you notice the engine temperature rising regularly, this can be caused by problems with other parts of the coolant system too, so it's best to get it checked out as soon as possible.
This can be caused by internal problems in the water pump such as a damaged impeller or leaking seals. Damage to the rotating impeller fins will affect how efficiently the water pump actually pumps the coolant around the engine. If it's not pumping the coolant as quickly as it should, this can contribute to the engine overheating, especially on a hot day or if you are stuck in traffic without much air coming in through the radiator.
An over heating engine can also be caused by lack of fluid in the coolant system. Even a small leak from the water pump can cause the coolant levels to drop fairly quickly, and this can have devastating affects on the ability of the engine to stay cool.
If the engine overheats it can be a sign that the water pump has failed completely, so you should not drive the vehicle until you get it checked out so as to avoid a costly repair bill.
What is a water pump and where is it located?
The water pump is usually a belt driven (or sometimes electrically driven) engine component that uses the rotation of the engine crankshaft to rotate and to pump coolant around the engine.
It is usually located on the front or on the side of the engine, and it's location depends on the type of engine and how the water pump is driven.
If it is driven by the timing belt, it is often located on the lower side of the engine as part of the timing belt set up. On other vehicles, and those that have a timing chain fitted, it may be located to the front of the engine behind a serpentine belt that may also drive the air conditioning and alternator.
What causes a water pump to fail?
A water pump can fail for many reasons, these include leaks from the shaft seals, damage to the impeller blades, bending of the impeller shaft, worn out bearings and cavitation on the inside of the water pump.
A well made, factory fitted water pump should last at least 100,000 miles or more, especially if the engine has been well maintained.
Premature failure of a water pump is usually caused by using the wrong type of coolant, or by not regularly changing the coolant and flushing the coolant system.
Here are some of the most common causes of water pump failure and coolant leakage.
1. Contaminated coolant
A very common reason for premature failure of a water pump is contaminated coolant. This can happen for a variety of reasons, but the most common is neglect.
When the engine is running, coolant can be pumped around the engine at a rate of 80 to 100 litres per minute. Over time, the coolant will degrade and can collect contaminants from the engine and radiator as it is pumped around. These particles can build up in the coolant if it is not changed regularly, and if the system is not flushed from time to time.
If dirt or debris find their way into the water pump, they can clog the impeller fins and wear away rubber seals. This will cause the water pump to eventually fail.
2. Using non-compatible coolant (mixing coolants)
All vehicle manufacturers recommend a specific type of coolant for their vehicles. It's important to use the recommended fluid when changing the coolant, as the wrong type can not only cause damage to the water pump, it can also lead to damage of other parts of the engine.
Traditionally, engine coolant was made by mixing distilled water with either ethylene glycol or propylene glycol based antifreeze. Today, most vehicles use organic acid technology (OAT) antifreeze or HOAT antifreeze that contain inhibitors to extend the life of the coolant.
Glycol based coolants are often green or yellow in color, whereas extended life OAT based coolants are more often dyed red in color.
When it comes to choosing a coolant (or antifreeze) there are lots of different options, and it can get confusing. I'd recommend choosing an OEM coolant directly from a dealership if possible.
Using the wrong coolant or mixing and diluting the coolant will affect the properties of the coolant and make it less efficient when it comes to cooling the engine. It can also reduce the effectiveness of the antifreeze additives that protect against corrosion. This can lead to increased corrosion and damage to the water pump, radiator, radiator hoses and cylinder gasket.
3. Improper installation of the water pump
Sometimes, premature failure of the water pump can be caused by improper installation of a replacement pump and not adhering to manufacturer guidelines.
When it comes to fitting a new water pump, it's important that the correct gasket or mounting surface sealant is used. Some vehicles use a thin gasket that is fitted 'dry' to the back of the water pump before installation. In most cases, you don't need a sealant with this type of gasket.
If the manufacturer recommends using a sealant, then be sure to use the correct type of sealant and don't use too much. If too much sealant is used this can leak into the water pump when it is fitted and can damage the inside of the pump or contaminate the coolant.
It's also very important to tighten the water pump fixing bolts to the correct torque. This will ensure the gasket/sealant seals properly and doesn't leak.
4. A badly aligned (misaligned) drive belt
If the serpentine or timing belt that is running the water pump is not fitted properly, this can put extra strain on the water pump pulley and cause premature wear.
Problems caused by a misaligned belt will put extra strain on the pulley shaft and bearings as it rotates. This can quickly result in worn out bearings or even bending and shearing of the shaft.
A belt can become misaligned if it is fitted incorrectly or not tensioned properly. It's not uncommon for a belt to move about on the pulley if it is nearly worn out or if it becomes contaminated by dirt or fluids such as engine oil, coolant or power steering fluid.
If there is a problem with the fitment of a drive belt it will usually result in a screeching or chirping noise that will increase in velocity and volume with an increase in engine speed. It's important to check any suspected belt noises promptly to prevent damage to the water pump or other engine components.
5. An over tensioned drive belt
If a drive belt is too tight, this can put an unnecessary strain on the water pump pulley and pulley shaft. Over time, this will cause premature wear and failure of the water pump. It also puts extra pressure on the water pump bearings, causing them to wear out more quickly.
Most modern vehicles use automatic belt tensioners, where the tensioner spring sets the correct belt tension automatically. Older vehicles may use manual belt tensioners, where the tension of the belt must be set manually and checked periodically.
It can take some practice to correctly set the tension of a belt. Generally speaking, there should be between one quarter and one half of an inch deflection on a correctly tensioned belt and it should run quietly with no squeaks or chirps.
how to replace a bad water pump
Replacing a water pump is not too difficult, provided you can get easy access to the pump and it's retaining bolts. It's recommended to replace the water pump when the timing belt, tensioners, pulleys are due to be replaced. Most of the time, the water pump will still be in good condition, but because of the amount of labor involved, it's better to do it when it's accessible.
If the vehicle doesn't have a timing belt, then it can be a lot easier to access the water pump. The replacement process is going to be different for every vehicle, as there is usually a lot of other parts that need removing before the water pump can be replaced.
Here's an overview of the water pump replacement procedure that applies to most vehicles.
- Wait until the engine is cool and drain the coolant via the radiator drain bung or by removing a coolant system hose. Be sure to have a large basin or bucket to hand, most coolant systems contain over 10 litres of fluid.
- Refer to a vehicle specific service manual, and follow the instructions for removing the timing belt cover, timing belt and any other engine components that need removing.
- Once you have access to the water pump, remove the coolant hose carefully from the front of the water pump. There may be a thermostat connected to the front of the water pump too, remove this carefully for reuse with the new water pump.
- Loosen the water pump retaining bolts carefully and remove the pump and gasket from the engine block.
- Carefully clean the mating surface of the engine block with some fine wet and dry sand paper if necessary. This surface must be perfectly flat and free from rust, dirt, old sealant or gasket.
- Check the fitting instructions for the new water pump, and verify if sealant and or a new gasket is necessary. Fit the new water pump as per the instructions. Be careful not to apply too much sealant to the mating surface of the water pump if used. Excess sealant can spread to the inside of the pump and cause problems when it sets.
- Check for the specified torque in the water pump fitment instructions. Torque the retaining bolts in diagonal order and to the specified torque. Water pump bolts are not heavy duty and the torque is usually fairly low, around 10Nm (or approximately 80lb-in), so be extra careful when tightening.
- Refit the thermostat (if fitted), and coolant hose. Rotate the water pump pulley by hand a few rotations to ensure it is working smoothly.
- Now fit the new timing belt kit and refill the coolant system.
- Double check that everything is fitted properly and rotate the engine crankshaft manually a few times to ensure that the timing belt is tensioned properly and is aligned properly on the water pump pulley.
- Run the engine and bleed the coolant system as per manufacturer guidelines.
- Check for leaks around the water pump seal. It's normal to see a very small trickle of coolant coming from the water pump weep hole for the first few minutes until the internal seal is settled into place.
- Turn off the engine, replace the timing belt cover, and other components removed earlier. Check the coolant level and top up as necessary.
Here's a really informative video that outlines the process involved in replacing a timing belt and water pump on a Lexus Toyota V6 engine.
water pump replacement cost
The average cost of replacing a water pump can be anywhere from $150 to $800.
There can be a massive difference in cost between vehicles and this is usually down to differences in the amount of labor involved.
An average water pump and replacement kit can cost from $40 to $150 to buy. If a timing belt kit is needed this can cost another $50 to $180.
Replacing a water pump can take 4 to 6 hours for a skilled mechanic, so you can expect to pay anywhere from $400 to $600 in labor costs. If the water pump is easy to access, the labor involved can be as little as 1 to 2 hours and $80 to $160.
Here is a table I have put together of approximate water pump replacement costs in 15 popular vehicles. These prices do not include replacement of timing belts, serpentine belts, pulleys or tensioners that are regularly changed with a timing belt. All parts are dealership OE sourced or from manufacturers such as Gates.
Water Pump Parts
$140 – $170
$80 – $120
$220 – $290
Chevrolet Silverado (timing chain)
$150 – $200
$300 – $380
$450 – $580
$150 – $200
$250 – $340
$400 – $540
$260 – $390
$220 – $420
$480 – $810
$200 – $360
$90 – $200
$290 – $560
Nissan Altima (timing chain)
$210 – $300
$110 – $150
$320 – $450
$160 – $210
$90 – $190
$250 – $400
$200 – $290
$100 – $150
$300 – $440
$250 – $300
$550 – $700
$450 – $580
$130 – $160
$580 – $740
$500 – $700
$200 – $250
$700 – $950
$380 – $490
$90 – $160
$470 – $650
$350 – $470
$100 – $140
$450 – $610
$530 – $650
$420 – $500
$950 – $1150
1. when should you consider replacing the water pump
The water pump should be replaced when it starts to show symptoms of failing. If the water pump is leaking coolant from the mounting seal or from the impeller shaft, then it is going to fail completely at some stage. If the bearings are worn or the pulley feels loose or makes a noise when rotating, this is also a sign of a failing water pump.
It's also advisable to change a water pump as a preventative measure when the timing belt is being changed, or if the engine has covered over 100,000 miles and the water pump has never been changed.
2. is it safe to drive with a bad water pump?
No, you should not drive a vehicle with a broken water pump. If it is showing signs of failing, you can still drive it, but you should get it replaced as soon as possible before it fails completely. Small leaks from the weep hole or dried coolant around the edge of the water pump are common signs of a leaking water pump and can get worse over time if not fixed.