Function of a Water Pump
The function of a water pump is to move coolant through your cooling system such that it passes through the engine block, hoses, and radiator to remove the heat the engine produces during operation. In most cases, the water pump is driven via belt that spins the water pump pulley to mechanically generate the pumping action that forces coolant flow through your cooling system. This belt is usually a serpentine belt on modern cars whereas some older vehicles have a dedicated belt specifically for the water pump. In rare cases, the water pump may also be driven by a chain or gear drive.
Common Symptoms of a Bad Water Pump
While water pumps are relatively simple devices, failures do occur occasionally. The following are the most common symptoms that you may encounter that indicate that you may need to replace your water pump:
Your Engine Overheats – A failed water pump can sometimes seize, which prevents it from circulating coolant through your cooling system. Without circulating coolant, your engine temperature can easily climb quickly to the point where your engine overheats, which you will notice since your water temperature gauge will begin to climb. If you continually run the engine in an overheated state, a cascade of failures can occur that includes blown cylinder head gaskets, warped cylinder heads, warped pistons, or failing seals. If you notice your engine temperature starting to climb, it’s time to pull over and shut the car off immediately to avoid causing further damage until you can diagnose the issue.
Coolant Leaks – Your water pump is sealed to the engine block with a gasket and is also connected to hoses. Each of those seals can begin to leak over time. In addition, some water pumps have a weep hole feature built in that can start to trickle coolant by design when the bearing starts to wear. In either of the aforementioned circumstances, you may start to see small drops of coolant near the front of the engine or find a small puddle on the ground underneath the front of the engine. When you notice leaking coolant, the water pump is one of the usual suspects.
The Pulley is Loose or Making Noise – The pulley that turns on the belt is either pressed on the water pump shaft or fastened on with a few bolts. It shouldn’t make much noise, but over time you may start to hear it whine or hum while the engine is running. There is a bearing on the shaft, and as it wears out, the pulley will make more and more noise. If a water pump is making noise, it’s time to replace it before it fails completely and puts other components in your engine at risk.
Replacing a Water Pump
When you’ve determined that your water pump needs to be replaced, the first thing to remember is that you want to work on a cool engine and wear the proper protective gear like mechanic’s gloves to protect your knuckles and safety glasses to protect your eyes.
Note: The example steps below are intended for general informational purposes solely to help give you an idea of project difficulty and tools required. As all cars are engineered differently, repair procedures and safety hazards vary from vehicle to vehicle. To ensure that you have a vehicle specific repair procedure and an exhaustive list of potential safety hazards, we advise you reference a factory service manual for your vehicle. Similarly, referencing a repair manual such as Chilton or Haynes might serve as a less expensive alternative.
Step 1 – With the engine off and coolant cold, find where both your water pump and radiator cap are located.
Step 2– Remove the radiator cap from the radiator. If you don’t have a radiator cap, look for the expansion overflow tank that is connected to the radiator. It should have a cap that you can remove in lieu of the radiator cap. Take care to keep contaminants from entering your cooling system while you have the cap open.
Step 3– Place a clean catch container under the lower radiator hose or preferably the radiator drain petcock if your radiator has one. Open the valve or remove the lower radiator hose from the radiator (using a screwdriver to remove the hose clamp) to allow the coolant to drain from the cooling system. Taking off the cap in the previous step will allow ambient air to enter the system as you drain your coolant which will reduce bubbles and splashes as you fill your catch container.
Step 4 – Remove the drive belts from the front of the engine. The belt is usually under tension provided by the manually adjustable alternator tensioning rod for older cars or the spring loaded serpentine belt tensioner if you have a newer vehicle. You need to use an open wrench to loosen the alternator tensioning rod or use a belt tensioning tool specific to your vehicle (although sometimes a deep socket and a breaker bar will work depending on the vehicle) to release the tension on the belt and remove it. This is a good time to inspect the condition of the belt to make sure there are no cracks. If there are, it’s worth replacing. It’s also worth noting that when de-tensioning a spring loaded tensioner, the stored energy in the spring as you de-tension can fling your tools around if you let go of them or aren’t careful.
Step 5 – Remove any hoses that are connected to the water pump. They may be held on with a worm gear clamp that you can loosen with a screwdriver, or by a spring clamp that needs to be removed with a pair of pliers. Inspect the condition of the hoses and plan to replace them if they are dry, cracked, or otherwise deformed.
Step 6 – Remove the water pump from the engine. You will need to remove the bolts and then gently wiggle the water pump loose from the engine. Avoid prying as you can nick the sealing surface on the engine which can cause future leaks. Use a gasket scraper to clean the mounting surface and prepare to put a new water pump on.
Step 7 – Install the new gasket and new water pump. We should note that we tend to avoid using silicone gasket maker unless special circumstances warrant (or your car requires it for some reason). Once in place, tighten the fasteners on the water pump to the manufacturer suggested torque using a torque wrench.
Step 8 – Reinstall all hoses and belts by reversing the procedure you used to remove them. Adjust belt tensioners appropriately such that belts have correct tension. For manually tensioned belts, take care not to overtension otherwise you will place undue wear on your alternator and water pump bearings which will lead to premature failure.
Step 9 – Reinstall the radiator drain plug if removed or tighten the petcock if loosened.
Step 10 – Fill the radiator with fresh coolant (usually a 50/50 coolant & distilled water mix but double check your vehicle manufacturer’s recommendation in your owner’s manual). If you need to mix your coolant with water, make sure to use distilled water as the minerals have been removed and won’t cause your cooling system any harm. Tap water still has minerals present and they can clog your radiator over time.
Step 11 – This step is optional, but you can pressure test the cooling system using a pressure tester. This will ensure the system has no leaks after reinstallation.
Step 12 – Bleed your cooling system. To do this, we recommend you follow the instructions from the manufacturer to make sure you complete this step safely. Also, remember that the coolant will be hot and can cause risk of burns, so take appropriate precautions before attempting to bleed your cooling system. The procedure varies depending on vehicle, but the general principle is that you run your vehicle while allowing air to escape your cooling system as it rises to the highest point. This is usually accomplished by running it with the radiator cap off or by opening a bleed screw depending on the vehicle. You will typically want to do this with your heater running at full blast to make sure you get air out of the coolant in your heater core. Be sure to watch your engine temperature closely to avoid overheating and continue to top off the coolant as necessary.
Step 13 – When the system has no air left, reinstall the radiator cap or close the bleed screw securely depending on which bleeding method you used. Drive the vehicle to verify that the job is complete and the vehicle operates normally. If the vehicle runs hot, stop, double check everything was installed properly, and then repeat the previous step as this likely means air is still trapped in your cooling system.
Step 14 – After the test drive, allow the vehicle to cool down and double check your coolant level to make sure you were successful in bleeding the system.
Best Water Pump Brands
When it comes to selecting the best replacement water pump for your vehicle, there are many brands out there to choose from and the decision is not always easy. To help narrow your search, we have provided a short list of our favorite water pump brands below as they provide high quality parts that withstand the test of time.
Cardone
Cardone has manufactured millions of water pumps over the years and have the process down to a science. They produce high quality parts at budget friendly prices. Depending on the pump, they use bearings made from heat treated steel. Depending on the expected offset load (from engine belts) which is tied to vehicle make and model, some pumps have a stronger ball or roller bearing to ensure a lengthy service life. Overall, Cardone makes a great choice when it comes to replacement water pumps.
Click here to find a Cardone water pump for your vehicle.
GMB
GMB makes great water pumps that last for the long haul. Their bodies are typically made from robust materials such cast iron or die-cast aluminum. They also use steel flanges and long-lasting bearings. Their quality is consistent so you’ll never have to guess whether the part you got was going to be a good one, which can be an issue with some of the less expensive brands. Overall, if you use a GMB water pump, we think it will treat you well.
Click here to find a GMB water pump for your vehicle.
Airtex
Airtex is part of ASC. Their pumps have a variety of features that make them an ideal choice for peace of mind that your water pump will both fit well and perform well. Some notable features of Airtex pumps are the machined mounting surfaces to enhance sealing. The bearings are also permanently lubricated which means that they have great wear resistance which greatly reduces your chances of having to replace a water pump again in the future.