Water Leaking from Under the Car — Why and What to Do?

Have you ever seen any stains, puddles or drops of liquid that seem to drip out of your car? Our cars have a range of various fluids necessary to keep them working as smooth as possible. With time, some of them can leak as a result of deterioration, cracking or other similar damage.

When this happens to your car, it will leave stains underneath it while parked. If you notice anything like this on your driveway or in a garage, try to track down the source of the leak as soon as possible. This article will help you understand what kind of fluids can you find under your car and how to deal with them.

Water leaking from under the car.

What Kind of Leaks Are There?

With so many various fluids flowing throughout your car, it can be difficult to figure out which of them leaks. Start by inspecting the fluid you’ve found underneath your car by checking the color and rubbing it between the fingers.

Oil Leak

Oil feels greasy and slippery, with black or brown colored being the engine oil. If the oil has a red or green shade, then you might have a power steering or transmission leak.

Coolant Leak

However, if the fluid has a water-like feel to it, is is more likely your car has developed a coolant leak. Although you might expect it to be clear like water, don’t get confused if the coolant shows a shade of some color. Assuming you are taking proper care of your car, there will be an antifreeze mixture within the cooling system. Depending on the type of antifreeze used, the coolant can be blue, pink, or yellow

Windshield Washer Fluid Leak

Besides engine related leaks, you can also have a cracked washer bottle or broken hoses that connect to nozzles on the hood. If this happens, the windshield washer fluid leak either all the time or when you pull the wiper stalk. Although this issue is not as serious as coolant or an oil leak, being left with no washer fluid can be annoying. And it can even be dangerous when you are driving on dirty roads, as it impacts visibility.


There is also one benign reason that can cause water leaks to appear underneath your car. When you turn on the air-con, it causes vapor to condensate within the ventilation system of your car. This water then flows down a simple hose and drips down to the road, where it can create a small puddle. It is very common for drivers to think this is some kind of leak.

How Does a Cooling System Work?

A cooling system in your car removes excess heat from the engine by transferring it into the car interior or the atmosphere using heat exchangers called radiators. To perform its job, the cooling system must cool the engine enough to prevent damage while keeping the engine warm enough for efficient operation. In addition, the cooling system must work in all operating conditions, adjusting to changes in engine load, vehicle speed, and outside temperatures. Finally, it needs to be sturdy enough to contain increased pressures created by engine heat.

Cooling systems in most modern cars use the same components. Inside the engine, a water pump uses an engine-driven impeller to draw water from the radiator and pump it into the engine water jacket. Inside the engine, the water pump sends coolant through the engine block and cylinder head, reducing combustion chamber temperature. A thermostat controls coolant flow between the engine and the radiator depending on running temperatures. 

Outside the engine coolant hoses provide a path for the coolant. They have a rubber and fabric structure to help isolate engine vibrations from external components. The radiator and cabin heater are heat exchangers, made out of sets of tubes with fins attached to them. As coolant flows through them, radiators send excessive heat into the outside air and also warm up the passenger compartment.

Last, there is an expansion tank and radiator cap, placed at the highest point. The cap allows pressure to build in the cooling system and releases it if goes above the designated value. To prevent boiling, the cooling system operates under higher pressure. This increases the boiling point and maintains cooling efficiency.

What Is the Difference Between the Coolant and Water?

To carry heat from inside the engine to the atmosphere, the cooling system uses a liquid called coolant. Although some car owners choose a cheap route and use tap water for this purpose, there are several strong reasons against this. The most obvious is that pure water freezes at 0 degrees. When frozen solid, water cannot flow and can cause water pump damage. In addition, frozen water expands and can lead to cracks in the engine block or head. Using coolant, which is a mixture of distilled water and antifreeze, lowers the freezing point.

To meet strict emissions and fuel efficiency demands, modern engines operate at high temperatures. Besides its antifreeze properties, coolant raises the boiling point. This helps prevent engine overheating during summer and under extreme loads. In addition to allowing corrosion inside the engine and cooling system, tap water also has poor lubricating properties. Coolant has special additives, which prevent damaging engine corrosion and lubricate the water pump seal.

What Causes Coolant Leaks?

As the engine in your car runs at operating temperatures, the cooling system car has to cope with several challenges. Besides increased pressures, there are also stresses caused by temperature changes and high-velocity coolant flow. Because of these harsh conditions, any cracks or damages within the cooling system will cause an immediate leak. Sometimes, this can be so intensive that it causes major coolant loss and engine overheating in just several minutes.

Besides being caused by cracks and ruptures, coolant leaks can result from engine overheating. If the engine temperature is too high, it will increase the pressure inside the cooling system above allowable levels. When this happens, the expansion tank cap will open and let some steam and coolant out of the cooling system to ease the pressure. The most common causes for overheating are clogged radiators, broken water pumps or a cracked head gasket.

How Can I Track Down Coolant Leaks?

With the cooling system being complex and having many components, tracking down leaks can sometimes be tricky. While liquids flow and drip over various parts inside the engine bay, they can hide the actual source of the leak in areas that are not accessible. However, there are several common failure points that you should check when looking for coolant leaks.

Check Rubber Hoses

Some components that can fail easily are rubber hoses, which connect the engine with other parts like the radiator or cabin heater. They must be both strong and flexible to withstand the pressure and vibrations that happen during engine operation. Make sure that coolant hoses in your car doesn’t feel hard like a plastic tube and that there are no swelling or bulges on them. Any of these symptoms call for an immediate replacement, as hoses like that can burst with no prior warning.

Check Radiator

Another common issue is a leaking radiator, as it can suffer from damage caused by flying rocks and other road debris. Besides this, there are also issues caused by corrosion, which can work its way through the radiator walls and cause leaks. Although there are various additives that claim to stop small radiator leaks, these can cause even more damage. If your radiator is leaking, replacing it is the only solution that guarantees long-term reliability.  

Check Coolant Pump And Thermostat

Both the coolant pump and thermostat assembly are the next place you should check for leaks. The most common failure points here are the coolant pump gaskets and transfer pipe sealing rings. Sometimes, leaks will be present only under certain engine speeds or temperatures, so make sure to look at these components in various conditions. Have in mind that these parts can be hard to see, so take your time when checking them out.

Other Things to Check

In the end, there are several basic things you shouldn’t oversee, such as loose or  mis-positioned hose clamps. And if over-tightened, they can slice the hose underneath over time. Other thing to check is the expansion tank cap, as it has to hold the pressure within the cooling system when the engine reaches the operating temperature. Faulty cap will allow coolant to escape out of the expansion tank even under normal operating conditions.


As you may have seen in this article, stains and leaks under your car can have various sources. When trying to find the root of this problem, you must first determine what kind of fluid is dripping out of your car. If it is oil, the problem could be with leaking engine, transmission or power steering. Water-like stains suggest either windshield washer fluid or coolant leak, which is more severe. Whatever the cause of the problem, you should solve it as soon as possible to avoid any further damage to your car.




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