The water pump is one mighty, hardworking automotive component. According to The Drive, it pumps “over 100 residential-sized swimming pools worth of water throughout its lifetime,” keeping the engine, hoses, and radiator at a constant temperature.
Given its Herculean task, bad water pump symptoms are typically anticipated between 40,000 and 100,000 miles (or earlier than this mark).
Symptoms of a failed water pump include engine overheating, grinding or thumping noises, visible coolant leaks, and high-temperature readings. They typically result from climatic conditions, insufficient coolant, or worn water pump components — disregarding any of which is ill-advised.
More specifically, here are the 11 most common symptoms of a bad water pump:
- Leaking Coolant
- Outlier Temperature Readings
- Engine Noises
- Gunk Deposit
- Cavitation
- Frequent Serpentine Belt Issues
- Moisture Around the Timing Belt Cover
- Leaking Weep Hole
- Corrosion
- Overheating Engine
- Radiator/Alternator Steam
Consequent problems arising from a car water pump gone awry are not only costly but also troublesome. And this is true whether or not underlying issues are promptly addressed.
Therefore, it is only sensible to recognize failed water pump symptoms early on and curb unpleasant aftermaths as soon as possible.
Symptoms of a Failing Water Pump
1. Leaking Coolant
Seeing puddles of antifreeze fluid on the ground (or your garage floor) is perhaps the most prevalent failing water pump symptom. While spotting these multicolored puddles is easy, resolving the leak is not as straightforward.
However, do not be discouraged, as coolant leaks are usually attributed to damaged gaskets (view on Amazon), cracked seals, and other worn-out cooling system components.
In extreme climatic conditions like winter, water pump components made of plastic (like impellers) have a higher propensity to break. This happens even when there is an adequate amount of antifreeze in the system.
Nonetheless, experienced car owners and mechanics still encourage maintaining ample amounts of antifreeze to keep the water pump healthy.
2. Outlier Temperature Readings
High-temperature readings from your vehicle’s water temperature gauge are a symptom of engine overheating and something to watch out for. Ideally, they should not occur, as they indicate that early water pump failing symptoms have been disregarded (inadvertently or otherwise).
Regardless of their underlying causes, these red-zone readings signify that the water pump is not circulating sufficient coolant through the engine block. If not addressed, the problem can result in damaged cylinders and the head gasket and serious damage to the engine block — neither of which you would want to happen.
3. Engine Noises
Pump-related noises typically sound like squealing, thumping, or grinding noises. At other times, you may perceive rattling noises or a clicking sound. Depending on what you hear, the noise could indicate an issue with a specific part or component.
A low-pitched grinding sound is usually associated with a compromised water pump pulley or bearing. Squealing noises also signify damage to the pulley but in its advanced stage — often when the serpentine belt (view on Amazon) has already snapped.
Rattling sounds trace back to bad bearings or a damaged impeller shaft (further linked to improper timing belt installation). And sometimes, the same culprits cause clicking noises instead of rattling.
On the other hand, whining or groaning indicates a loose drive belt or jeopardized water pump pulley.
As soon as these noises become apparent, consult a mechanic immediately. They will inform you whether you need only replace a bearing or the entire water pump.
You can take on this challenge if you are mechanically inclined. But be warned, as you may have to replace the water pump and timing belt simultaneously.
4. Gunk Deposit
Because a water pump can fail due to coolant leaks, you can expect to see a gelled deposit around the pump and outside of the cooling system while inspecting the component. Note that there will be no puddle underneath your vehicle.
The reason for the absence of antifreeze spills is that the leak in the cooling system is a slow one. That said, feel free to suspect your car water pump when this happens.
5. Cavitation
Dubbed by Tire Review as the “killer of water pumps,” cavitation (not the body-slimming technique) is among the bad water pump symptoms that catch your attention only when damage has been done.
In this scenario, voids containing super-heated vapor wreak havoc on metal and plastic water pump components. But you would not know the full extent of the damage unless you remove the pump and thoroughly inspect it.
The movement of the water pump’s impeller shaft against the coolant generates these voids (which look like termite-eaten metal when imploded). Furthermore, an imbalance between vapor pressure and Net Positive Suction Head available or NPSHa (aggravated by restrictions in the system) determine whether or not voids will occur.
The overall health of the cooling system and the dilution of coolant used in a vehicle’s cooling system also directly affect cavitation. If the antifreeze-to-water ratio is too high in hot weather, it may increase the likelihood of engine overheating and cavitation in water pumps.
6. Frequent Serpentine Belt Issues
Serpentine belts are worth keeping an eye out for if you suspect your pump has started failing. After all, they are the impeller’s power source and, when defective, can cause hub/pulley malfunction.
Note that issues with serpentine belts are not exclusive to water pump failure. Nonetheless, it is easy to spot one in poor condition, as it will have cracks or frayed nylon chords.
On average, the service limit of a serpentine belt is between 60,000 and 100,000 miles. Ideally, belt-related problems should occur within that duration.
If issues with the belt happen more frequently than expected, check if you have one of these three problems — a misaligned pulley, faulty belt tensioner (view on Amazon), or defective water pump bearings.
7. Moisture Around the Timing Belt Cover
For automotive water pumps located under the timing belt cover, this telltale sign is a great way to determine if the pump is starting to fail.
Initially, it may appear as a small stain on the timing belt cover. But as water pump issues worsen, this muggy stain tends to become more visible.
Sometimes, oil leaks resemble how moisture around the belt cover would look like. If so, ascertain that the stain is caused by a coolant leak and not oil by sense and smell. Coolant has a distinctly sweet, sugary smell and does not feel greasy to the touch.
8. Leaking Weep Hole
Functionally, a weep hole (found on the water pump body/housing) is like the tread limit indicator in tires. This built-in outlet is where water drips from when pump failure is imminent.
Except during its pre-break-in period (when a water pump is just newly installed), no water or any fluid should be able to seep through this vent.
That said, water seepage through and bleed marks around the weep hole likely indicate a failing water pump. To resolve this, thoroughly flush the cooling system and ensure that the coolant you will refill it with is up to spec and not contaminated.
More importantly, refrain from dry running your water pump to prevent its mechanical seal from breaking.
9. Corrosion
Water pump corrosion is often a result of incorrect or improperly mixed coolant and is one symptom that should be avoided at any cost. The main reason is that it can cause several issues in the water pump’s operation.
Important parts, such as the impeller and pulley, usually take the brunt of rust formation, resulting in belt slippage and premature water pump failure.
10. Overheating Engine
Engine overheating occurs when a car owner has failed to take notice of all the other signs in this list. This red flag is definitely hard to miss, although spotting it does not necessarily mean that your car water pump is defective.
It is a known fact that many factors lead to overheating — including a plugged coolant hose, a defective radiator fan, a cooling system leak, and thermostat failure.
Outside the cooling system, the symptom is also linked to a clogged heater core and depleted engine oil levels.
Some cues to watch out for that signify an impending (or ongoing) overheating issue include visible steam or vapor from under the hood and illuminated warning lights on the dash. Additionally, be alert for acceleration and performance issues or if you get a whiff of butterscotch or maple-syrup-like smell.
11. Radiator/Alternator Steam
One of the clearest signs of water pump failure is when white smoke is visible from your vehicle’s front end and coming out of your radiator or alternator. It is typically caused by engine overheating and radiator cap problems, meaning that your failing water pump is already that far gone.
Should you encounter this problem while on the road, make sure you pull over to safety and call roadside assistance.
Bad Thermostat vs. Bad Water Pump Symptoms
A bad thermostat shares similar symptoms with a failing water pump since it is connected to the water pump system. But unlike the latter’s designated components, it is tricky to determine whether or not a thermostat is stuck.
To work around this dilemma, experienced car owners recommend checking both components for issues to ensure the thermostat is not overlooked or disregarded.
Causes of Water Pump Failure
- Vibrations
- Extreme temperatures (winter)
- Damaged or leaking mechanical seal
- Loose or damaged water pump pulley
- Worn-out water pump bearings
- Fouling of internal surfaces
- Compromised timing belt or serpentine belt
- Impeller failure
- Belt tensioner failure
- Worn-out axle
- Use of incorrect coolant
Car Water Pump Replacement Cost
Estimated costs for replacing a water pump vary depending on a vehicle’s year, make, model, and size. Typically, it would fall between $310 and $800 (parts and labor included but sans shop materials, extraneous fees, and taxes).
Parts alone can be as inexpensive as $70 or as pricey as $400. As for labor fees, expect to pay around $80 to $110 hourly if the replacement is tasked to a professional mechanic.
Prices are subject to change based on how far gone the failing water pump is and if repairs outside the water pump system are needed.
You can keep replacement costs to a minimum if you are mechanically inclined. However, you need an XHTT 216-Piece Socket and Wrench Kit (view on Amazon) to get things done.
Conclusion — Symptoms of Water Pump Failure
In conclusion, here are the 11 most prevalent bad water pump symptoms:
- Leaking Coolant
- Outlier Temperature Readings
- Engine Noises
- Gunk Deposit
- Cavitation
- Frequent Serpentine Belt Issues
- Moisture Around the Timing Belt Cover
- Leaking Weep Hole
- Corrosion
- Overheating Engine
- Radiator/Alternator Steam
This list does not include rough idling and oil contamination, as these indicators are often intertwined with fuel system problems. Nevertheless, they are encountered by many car owners and should be ruled out, too, when experienced.
In addition to this guide, many online resources provide a wealth of information on how to best identify and address these symptoms. I recommend using as many reliable references as possible to help nip water pump failure in the bud!
Kris is an avid off-roader and outdoor enthusiast who loves to brave the elements and take on challenging terrain. He also enjoys sharing his passion and knowledge with others so that they, too, can appreciate the ride.
About Kris