The car water pump is one more crucial part of the engine. This is why recognizing signs of a bad water pump is very important.

When it’s not working properly there isn’t a good flow of coolant which causes huge problems for the engine, like overheating.

So, knowing and immediately noticing the first signs of a bad water pump may mean the difference between a more or less simple repair and a partial engine rebuild.

If you want to see what are the most common reasons for an overheating car, click here.


Before we start with the most common signs of a bad water pump, it’s only fair to mention how does it actually work.

Car water pumps are very simple mechanisms. They are centrifugal pumps that are belt driven by the power of the engine.

So, the moment the engine starts running, the water pump creates a circulation of coolant inside the system.

The coolant then runs through the radiator (among other elements) which cools it down to a normal temperature.

This is a very modest and short explanation, if you’re interested in a more in-depth one, click here for a great explanation on Wikipedia (both for the water pump and the whole coolant system).

One more piece of information important for this topic: there are generally two types of car water pumps:

  • Driven by the serpentine belt or v-belt


These types of water pumps are visible on the outside of the engine. It’s easily recognized by having its own visible pulley and in some cases, coolant hoses attached to it.

To clarify, you can recognize it the same way as you would the alternator or the AC compressor, for instance.

Much better and less complicated system for making a repair.

  • Driven by the timing belt



This is standard for almost all of today’s engines.

Once, the timing belt was reserved exclusively for connecting the camshaft and crankshaft. In modern engines, they have inserted the water pump also.

You may ask yourself why they did this? Well, the good side of it is that your car won’t overheat if the serpentine belt snaps, which is really genius.

The bad side is maintenance.

If the water pump malfunctions prematurely for some reason, you have to take off the timing belt before replacing the pump.

Luckily, the service interval demands to replace the water pump every time the timing belt is changed in order to avoid problems.

If everything is done properly and with quality parts, you shouldn’t have any signs of a bad water pump during this period.


1. Coolant leaks


This is, in most cases, the first sign of a water pump problem.

If you see a small puddle under the car or traces of moisture where the water pump is located you should react immediately.

With serpentine belt driven water pumps, you perhaps have some more time to react as it won’t pose an immediate threat to the engine functioning.

But for timing belt driven water pumps react as soon as possible. Coolant may leak on to the timing belt causing it to slip and inflict some serious damage to the engine.

The most common reasons for this are:

  • Worn-out mechanical seals inside the pump itself

These are the seals that protect the inner part of the pump from getting in contact with coolant.

This problem is mostly solved by replacing the complete water pump.

In some rare cases, the pump can be dismantled and repaired but the price of labor and parts is such that it simply isn’t worth it.

Exceptions are older or more rare types of cars where parts are hard to find and the only solution is reparation.

  • Faulty gasket between the pump and engine block

If the pump is OK, this gasket is the next most common reason for a coolant leak. In most cases, it’s located on the water pump housing.


For more information on how to find and fix a coolant leak click here.

2. Moisture around the timing belt cover (for water pumps driven by the timing belt)


Leaks are harder to spot in this case as the water pump is under the timing belt cover.

But usually, at the beginning there is only a small leak which will first appear on the belt cover as a moisty stain.

Later, as the problem gets worse, coolant will drip from the cover on to the ground making it more visible.

Sometimes the stain can also be caused by an oil leak. The best way to tell them apart is by sense and smell.

If you can, try reaching the stain and rub it with your fingers. Then smell it.

Coolant has a specific smell, distinctive from engine oil and there will be no mistake if you have a coolant leak.

Also, it’s not as greasy under the fingers as engine oil is.

3. Frequent low coolant level


Leaks will mean frequent low level of coolant. If you didn’t spot any leaks, then this is the most obvious sign of a bad water pump.

You see, a bad water pump is rarely noticed right away. Except for more severe cases the leak can last for months before serious problems start.

The reason for this is the gradual material fatigue of the pump parts. In the beginning it’s just coolant moist and trickles which over time becomes a full-blown leak.

So, if you have to add coolant from time to time, check the water pump and the location around it as well as the rest of the coolant system.

The best way to spot a problem (water pump or otherwise) is to make regular checkups on your car.

If you have the time, check a separate page on this topic by clicking here and make check-ups a regular habit.

It will save you a lot of trouble and money over time, trust me.

On the other hand, if you want to see how to check only the coolant level, click here.

4. Overheating engine



If the engine starts to overheat frequently and the temperature gauge is constantly showing high temperature then you may have one more sign of a bad water pump.

Leaks and low coolant levels will cause this but there is one more reason regarding the water pump.

That is a faulty impeller. That’s the small turbine-like part connected to the pump shaft that actually pushes water through the system.

Two most common causes:

  • The impeller blades wear out over time. On lots of today’s pumps, the impeller is made out of plastic so it’s not that much of a surprise.
  • Faulty or worn out bearings on the pump; they cause the pump shaft and impeller to get out of line and grind against the pump housing.

Worn out impellers mean a weak flow of coolant. Simply, the proper pumping force can’t be achieved.

One more of those signs of a bad water pump that shows itself gradually.

Over time, it gets worse but luckily there is enough time to react under the circumstance that you pay enough attention (like watching over the temperature gauge, making regular check-ups, and so on).

The engine rarely overheats instantly if this is the problem.

If you ever get in a situation where the engine overheats, click here for a separate article that may help you in that situation.

5. Grinding noise from the engine bay

If you hear a grinding noise coming from the engine bay, this may be one more sure sign of a bad water pump.

The noise starts, in most cases, as barely noticeable and gradually builds up to an unpleasant grinding tone.

The main reason is the bearings inside the pump. You see, the shaft inside the pump (which is connected to the pulley and impeller) is held in place with bearings.

The bearings wear out due to material fatigue which is no surprise since the pump turns over billions of times in its service period.

Solve this problem as soon as possible especially if the pump is driven by the timing belt. It can jam the timing belt causing it to skip or even break!!
This can, depending on the engine design, cause major damage to the engine itself!
In the case of a serpentine belt, the belt can snap/break.

The bearing failure is usually accompanied by noticeable leaks before the water pump totally fails.

Complete replacement is the best solution here.

As mentioned previously some water pumps can be repaired through installing new bearings but this rarely the case, again because of the price of parts and labor.

Before any kind of repair just make sure to pinpoint the correct sound of the grinding noise as it’s not exclusive only to the water pump.

It may be caused by other devices with faulty bearings like the alternator, AC compressor, or else.

So, make sure what’s causing the noise before taking off the pump, especially if the timing belt has to be taken off.

6. Wobbling serpentine belt (for water pumps driven by the serpentine belt)


If you look at the serpentine belt while the engine is running and the motion is not linear but wobbling you might have a faulty water pump pulley.

Two main reasons for this

  • Pump bearings may be worn out

When the bearings inside the pump are worn out the shaft is not centered properly. Since the pulley is directly connected to the shaft, it too is not centered. Because of this, the wobbling appears.

  • Water pump pulley is faulty

The main reason for a faulty pulley is material fatigue or poor material quality. Constant strain and pressure over a prolonged period of time can damage the pulley.

  • Pulley is not properly tightened

This is rarely the case and is mostly caused if some previous improper work has been done causing a damaged screw, thread, it hasn’t been tightened properly, etc.

The screws or nuts that hold the pully have safety washers under them(or other systems) that secure these into place so the rotation force doesn’t accidentally take them off.

So, if no one touched it, you shouldn’t have these kinds of problems.


When the bearings are worn out, replacing the complete water pump is the best solution.

If the wobbling is caused by the pulley, in most cases, the pulley can be replaced separately.

Just make sure, as with the grinding noise, that the belt wobbling is actually coming from the water pump and not from any other device driven by the serpentine belt.

7. Frequent serpentine belt problems


Frequent serpentine belt problems are one more of the sure signs of a bad water pump.

Some of the most common are:

  • Serpentine belt wears out often

A faulty water pump pulley will damage the serpentine belt over a short period of time.

  • Screeching or squeaking sound from the serpentine belt

A squeaking sound is, mostly, caused by a faulty pulley or a severely worn out belt.

Screchhing appears when the pump bearings are the problem since the pulley is heavily turning. A sure sign that a total failure is near and that the pump will stop turning altogether.

Before the screeching sound, a grinding noise and coolant leak may appear around the water pump.

  • Broken serpentine belt

If you, for some reason, neglect the grinding noise, wobbling, and eventually the screeching sound, you’ll surely get a broken serpentine belt.

The water pump pulley will get stuck and in a short time, the belt will snap (break).

Of course, this can also happen if you haven’t changed the belt on time.

If you have to replace the serpentine belt and want to see how much it costs, click here for an article on that topic.

Besides this, you can read more about serpentine belt problems by clicking here.



Timely reaction and paying attention to these signs of a bad water pump is crucial and of the most importance.

Noticing and reacting on time can save both your engine and your budget.

Otherwise, in a worst-case scenario, the engine can overheat. the timing belt can break and this can lead to a partial or complete engine rebuild. If you want to read more on the engine rebuild topic, click here.

Also, make sure the car maintenance is done on time and with quality parts, especially when the water pump is driven by the timing belt.

Take this problem very seriously, tend to it as soon as possible and if you can, in more severe cases, avoid driving the car altogether.



Written by: Sibin Spasojevic


Former car technician, life-long car and DIY enthusiast, author for Despairrepair.com