The cooling system works to maintain temperatures in the engine by pumping coolant through the system. The movement of the fluids is controlled by the water pump, so if this component breaks down, you'll find the engine will overheat rather quickly.
Telltale signs of water pump problems
Diagnosing a faulty water pump can be tricky, as the signs could also point to problems with other aspects of the cooling system. Coolant leaks are often indicative of water pump issues. If you have low coolant levels, you should top off the fluid. Park the car overnight with a sheet of paper underneath the engine. If the paper is wet in the morning, whether it is clear or greenish in color, you'll likely need to check the water pump for further problems.
Locating the water pump
The location of this part may vary slightly from car to car, so if you need help finding it, the owner's manual is a good place to start. This will also contain information pertaining to the tools necessary for replacing the pump and how to go about doing so for your particular make and model. The water pump is attached to a pulley, which is connected to a belt that supplies power so the pump can run. This is generally behind the radiator, closer to the center of the engine block. This is when you'll appreciate having the owner's manual handy, as many different components of the car are coupled with pulleys and also located in the same area.
Checking for problems
There are a few things you can check to determine whether the pump is defective. First, inspect the belt for signs of damage. It may be that the pump simply isn't getting the power it needs to run properly. Inspect the pulley as well - it should not feel at all loose when you try to jostle it. If it has any give, this likely means the bearings are going bad and you'll need to replace the pump. Bad bearings typically also result in grinding sounds coming from the pulley.
Be sure to visually inspect the water pump. If there is a problem, you'll probably notice signs of coolant leaks on or around the pump. Check out the gasket that connects the hose to the pump as well. If it appears cracked, damaged or otherwise leaking, you'll need to replace it. This is also often a good time to replace the water pump as well.
Inspect the rest of the system
When one component of a system begins to fail, it can lead to damage in other areas. The different parts have also likely been working for the same span of time, which means they've all undergone heavy usage. Be sure to inspect hoses and seals for signs of damage as well and replace anything as needed.
Replacing a water pump
As mentioned earlier, the exact process of replacing a pump is very car-specific. Some vehicles are designed so the pump is easily accessible, while others may require you to remove other parts to access the pump. If you are uncomfortable dissecting your vehicle in such a manner, you can bring it to a mechanic. Troubleshooting the problem before you go in will help you better explain the situation to your mechanic. When the water pump is replaced, the coolant will also need to be drained and refilled.