What happens when water pump goes out while driving

In order to run cool on those hot summer days, your engine needs to have a consistent flow of coolant supplied from the radiator throughout the engine. The water pump is the primary component responsible for maintaining this flow. When it works properly, your car will maintain a consistent operating temperature, run smoothly, and take you anywhere you need to travel. When the water pump fails or is beginning to wear out, it can lead to complete engine failure.

When the water-cooled (as opposed to air-cooled) engine was introduced, many automotive experts believed that the water pump circulating coolant through the engine block was just as critical to engine protection as oil. This philosophy holds true even as technology improves over the years to create more efficient cooling systems in today's modern cars. Your car’s water pump is the key to making the entire system work. It is an impeller pump and is usually buried under the timing belt cover on the side of the engine. The pump is operated by the engine’s drive belt – as the belt turns, the pump turns. Blades on the pump force coolant to flow through the engine and back to the radiator to be cooled by a forced air cooling fan.

Although the water pumps in most modern cars, trucks, and SUVs will last a long time, they are by no means indestructible. Like any other mechanical device, they will produce a few warning signs of wearing out, so that car owners can contact a local ASE certified mechanic to replace the water pump before additional engine components are damaged.

Here are 5 common symptoms of a bad water pump:

1. Coolant Leak at the Front-Center of your Car

The water pump is comprised of multiple gaskets and seals that keep coolant contained and ensure that consistent flow of coolant is delivered from the radiator to the engine. Eventually, these gaskets and seals will wear out, dry up, crack or break entirely. When this happens, coolant will leak from the water pump and drop to the ground, typically in the front of your car and in the center of the motor's location. If you notice there is a leak of coolant (which will appear to be green or sometimes red in color) under the center of your car, truck or SUV, contact a professional mechanic to inspect this problem. More often than not, it's a leak from the water pump that can be repaired before it gets worse.

2. Rust, Deposit Buildup, and Corrosion of the Water Pump

Gradual leakage over time will cause different minerals to build up around the pump. Check under the hood, and you may notice rust on the pump’s surface from contaminated or non-compatible coolant mixtures or a defective pressure cap that lets in excess air. The wrong coolant will also cause deposit-buildup inside the pump, which slows the ideal process of engine cooling. In addition to these signs of wear, you may also notice small holes from corrosion in the metal, or cavitation – vapor bubbles in the coolant liquid that collapse with enough force to create cavities on the mounting surface. Should you notice these symptoms, replacement of the pump should be sought out immediately.

3. Water Pump Pulley is Loose and Making Whining Sounds

From time to time you might hear a high pitched sound that comes from the front of the motor. This is typically caused by a loose belt that creates a harmonic buzzing or whining sound as it circulates. The loose belt is commonly caused by a pulley that has become loose or that the bearings that operate the water pump assembly are wearing out. Once the bearings fail inside the water pump, it means the unit cannot be repaired and will need to be replaced entirely.

If you notice there is a loud whining sound coming from the front of your motor that increases in volume as you accelerate, contact a mechanic as soon as possible to inspect your vehicle.

4. Engine is Overheating

When the water pump fails completely, it will not be able to circulate coolant through the engine block. This results in an overheating situation and if not repaired or replaced quickly, can cause additional engine damage like cracked cylinder heads, pushed head gaskets, or burnt pistons. If you notice the engine temperature gauge runs hot on a frequent basis, it's more likely than not a problem with the water pump. You should contact a mechanic to inspect this problem and replace the water pump if needed.

5. Steam Coming from your Radiator

Finally, if you notice steam is coming from the front of your motor as you drive or come to a stop, it is an instant sign of an overheated engine. As discussed above, an engine will maintain a consistent temperature when the water pump works correctly and circulates water to a functioning radiator. If you notice steam coming from the front of your motor, you should pull over to a safe area and contact a mechanic as soon as possible. It's never a good idea to drive an overheating engine, so if you have to contact a tow truck to get the car home, this could save you significant money in the short and long term – it's going to be less expensive than replacing the engine entirely.

Anytime you notice any of these warning signs, contact a local ASE certified mechanic so they can repair or replace the water pump and get your car back onto the roads without delay.

There are some parts of a vehicle that, when failing, do not need to be immediately replaced. A water pump is not one of those parts. Due to the vital role the pump plays in cooling the engine, if it stops working, there will be fast consequences including possible all-out engine failure. Replacing a bad water pump isn’t a quick job, but it’ll save you from the worse job of replacing your engine. Know the signs of when you have a bad water pump on your hands.

Unhealthy Circulation

The water pump moves coolant through the radiator and around the engine to dissipate heat buildup. Rapidly moving, closely connected metal parts generate a lot of friction, and thus, heat. Too much heat and you end up with components that are warped, melted, fused, broken and otherwise structurally compromised. The water pump is usually pulley driven by the accessory drive belt, serpentine belt, or timing belt. A worn out belt can prevent your water pump from operating at peak efficiency. Internally, there is an impeller that keeps the system circulating. Over time the impeller can actually wear down due to contaminants in the coolant. Cavitation can also cause the impeller to erode and lose the ability to pump coolant.

Leakage

One telltale sign of a soon-to-be-faulty water pump is a noticeable coolant leak toward the front of the vehicle. If the car is left overnight and you notice an orange or green (depending on the coolant you use) puddle on the ground, suspect the pump. But don’t assume that a lack of coolant on the ground doesn’t mean you don’t have a water pump leak. If the coolant reservoir is low but there is no visible coolant leak, check your oil dipstick. If it looks frothy or like a chocolate milkshake, you may have an internal water pump leak. Certain Ford Duratec V6 engines can leak coolant internally behind the timing chain cover.

Ick

A slow leak over time will cause a bunch of gunk to build up around the pump. Look for coolant trails leading down from the pump, or a kind of gelled coolant deposit around the outside. Some water pumps have a “weep hole” beneath the pump shaft that will leak coolant once the internal seals have worn out, a sure sign of a bad water pump. You might also see a good deal of rust around the pump and, if you look closely, pitting (corrosion that creates small holes in the metal) or cavitation (formation of cavities in a liquid) on the mounting surface. All of this indicates a slow leak. While this doesn’t result in immediate failure, it will create a low-coolant condition (which is quite bad) and allow the lubrication protecting the moving parts inside the pump to escape (which will ruin the bearing).

Noise

A loose accessory belt will cause a whining noise that increases with acceleration. The fix for this could be as simple as tightening the belt, replacing the belt, or replacing the belt tensioner. If you hear a grinding or growling noise from the front of the engine, however, that indicates a bad bearing. There are other bearings on the front of the engine that can fail, but in any case you should immediately take it to a mechanic to confirm and repair the problem.

Overheating

Once the pump has failed, your engine will overheat. If you haven’t noticed other signs of impending failure, take note of this one. If the “Low Coolant” light comes on, add coolant ASAP and check for a major leak. If the temperature gauge rises above normal or a temperature warning light comes on, pull over and call a tow truck. Once the water pumps fails there is no safe amount of time you can run the engine without possibly causing serious damage. While turning on the heater may help cool down an engine with radiator issues, without a pump to circulate the coolant this trick won’t help in this case. The smart move is to park it.

Steam

If you see smoke or steam coming from your radiator or under the hood generally, your engine is too hot and has probably already suffered a lot of damage. Pull over immediately and call for help. Wait for the engine to cool off before poking around, as you’re dealing with scalding-hot coolant and potentially other unexpected dangers. Not only is your cooling system superheated, but it is also under pressure. It is best to wait a few hours for everything to cool down before beginning a diagnosis.

Because it’s located in the front of the engine behind the fan or crammed next to a strut tower, accessing a bad water pump can sometimes involve a significant amount of tear down. It’s definitely a pain of a component to have replaced, but it’s worth it. Do yourself a favor and pay attention to the warning signs before it’s too late for your engine.

Check out all the heating & cooling systems parts available on NAPAOnline or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on whether you have a bad water pump, chat with a knowledgeable expert at your local NAPA Auto Parts store.

Photos courtesy of Blair Lampe.