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Home / Symptoms / Car Leaking Water

Four common causes for leaking water from the vehicle and their related parts.

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Is Your Car Leaking Water?

The water leak is caused by condensation in the air conditioning system. In this case, don’t sweat; the leak is actually a designed condensation release as long as it is not leaking into the passenger compartment. However, there could also be serious reasons, like a window washer tube leak, damaged windshield, window or door seals, or sunroof leak.

If you see a puddle under your vehicle, check if it's a vital fluid, like coolant or engine oil. Sometimes, it may just be water. While leaking water usually isn't as catastrophic, water leaks can damage your vehicle.

Keeping your vehicle's interior dry and sealed is the key to preventing water damage. Unfortunately, finding the source of the leak isn't always easy and sometimes requires a technical solution.

Watch out: Water leaking into your vehicle is likely to develop problems. Aside from damage to your headliner and carpet, water can disrupt and interfere with the car's electrical system, causing a short circuit. Moist environments also present the danger of mold or mildew inhalation.

The most common causes for water leaking inside a vehicle

The most common causes for water leaking inside and outside your vehicle are:

Clogged air box drain: An air box drain, also known as an air filter housing, is an opening that allows water to pass. This water we're referring to is the one that gets in your vehicle through rain, puddles, or any external wet source. So, this water seeps inside your vehicle, passing through the air box drain, and getting safely disposed outside. But if the air box drain is clogged, the water can get stuck, making it seem like your vehicle leaks water.
Windshield leak: The windshield is the big wide glass covering the area from the driver's to the passenger's forward vision. It offers all sorts of protection against debris, wind, weather, etc. The windshield is tightly put in place through sealings and glue. If the windshield is too old, gets misplaced, or cracks, water might seep through the gaps and enter your vehicle's cabin.
Leaking doors: Your vehicle's doors have a sort of rubber sealing, which helps create tight pressure to keep the door gaps impenetrable by rain, debris, insects, etc. However, if this rubber is worn or cracked, or even if the door is bent and not shutting right, this sealing loses effect, allowing water to sneak inside your vehicle.
Leaking sunroof: Much like your doors, the sunroof has rubber sealings around it creating pressure to prevent water from entering your cabin. However, if this sealing is loose or worn, or if the sunroof glass is bent or cracked, water will seep through the gaps, entering your cabin.
Air conditioning condensation: Have you ever noticed how those air conditioning boxes that stay on the other side of the room's wall keep constantly dripping water when the air conditioner is on? That's a common condensation of water that all air conditioners do, and vehicle ACs are no different. When you activate your vehicle's AC, condensation starts, and water droplets might fall underneath the vehicle — that's normal!
Leaking window washer: When you push that lever — or press that button — to wash your windshield, soapy water comes from inside a container, travels through hoses, and leaps into your windshield; it follows a specific track. But, if anything in this track fails, for example, one of the rubber hoses the water passes through cracks, it'll result in leaks.

Frequently Asked Questions

Is there a puddle of water under your vehicle near the footwell after driving on a hot day with the AC on?

You may also smell a musty odor inside the vehicle, or the carpet on the passenger side may get wet.

The air conditioning freezes moisture in the air and condenses them on the evaporator core (where hot air is exchanged for cool air). This condensation drains into a catch pan attached to a drain hose. This hose is meant to discard the water under the vehicle. This is a normal part of a vehicle's functioning air conditioning process.
Is the carpet wet from water on the passenger side?

You may also hear a sloshing noise under the dash or feel cold water dripping on your feet while driving.

During the air conditioning, moisture in the air freezes and condenses on the evaporator core (where hot air is exchanged for cool air). This condensation drains into a catch pan attached to a drain hose. This hose is meant to discard the water under the vehicle, but if it's clogged, the condensation will accumulate in the catch pan until it overflows. This water winds up soaking the carpet on the car's passenger side without proper drainage.
Are there stains around the headliner near the sunroof?

You may hear a whistling noise while driving or find the trunk's carpets wet.

A vehicle's sunroof has a weatherproof seal between the glass and the roof. Since this seal is made from rubber, it degrades over time and with exposure to weather. If it gets brittle or torn, water can leak onto the headliner (the vehicle's ceiling liner), causing visible stains.
Is there water on your vehicle's dash when it rains?

You may hear a whistling noise while driving or smell a musty odor from the vehicle.

Modern vehicles use a high-strength adhesive to bind the windshield's glass to the frame. The seal will be breached if this binding material becomes stiff and cracks. This allows water to seep in during wet conditions, causing you to see droplets of moisture on the dash.
Do you hear a whistling noise when driving down the road?

You may also have intermittent electrical issues or find the carpet in the back seat is wet.

There is a continuous weather strip that forms an airtight seal around the doors of the vehicle. However, since the weather strip is made of rubber, it degrades and gets hard over time. As a result, opening and closing the car doors wear on it as well. Plus, if the weather strips no longer form an airtight seal, wind leaks in when you drive, creating a whistling noise as it blows through the breaches in the seal.
Is there a puddle of blue fluid under your vehicle after you use your windshield wiper fluid?

You may also find puddles of water under the vehicle near the floorboard or under the middle or back of the car.

The front windshield washer system comprises a reservoir, hoses, and spray nozzles. Unfortunately, any of these components can get damaged with age, wear, or exposure to weather. If this happens, they become brittle and crack, leading to leaks. These leaks allow blue windshield washer fluid to spill out and become puddles underneath the vehicle.

Typical fixes to address the cause(s)

These are typical processes and repair services that fix a check engine light issue

The most common cause: Air conditioning condensation

The most common reason for water leaking inside or outside a car is regular air conditioning condensation. The condensation from regular air conditioning commonly confuses drivers who believe something is leaking, becoming the most regular concern. The water that puddled under the vehicle after you parked is normal if you were driving with the AC on.

Symptoms it causes: Apart from water droplets under the vehicle, you shouldn't notice any other symptoms.
No risk of priority: The condensation and water droplets under the car are to be expected — nothing to see here. There's no damage happening if it's regular puddling that happens after driving with the AC on.

How exactly does condensation work?

The condensation is basically ice melting. Inside your vehicle's AC, there is a cold coil named "evaporator coil" that's extra freezing temperature. While the air conditioning cooling process is happening, warm air from inside your vehicle's cabin enters the AC system and reaches this freezing coil, making ice particles melt from it. This is like when you get a cup of water and it starts to sweat. The water resulting from this interaction is called condensed water, and this interaction is known as condensation. The condensed water goes through a drain system that disposes of it safely outside your vehicle.

Go safe: If you're noticing water puddling under your vehicle every time, even when you're not using the AC, or if the puddles are too large and frequent to be normal, consider having a DVI or a vehicle inspection. Better be safe.

What’s a vehicle inspection? It’s “detective work” on your vehicle, checking its systems to see if anything prevents the car from working as expected. In this case, mechanics examine different parts of your vehicle to track if anything is causing the water to leak excessively. They’ll also check the condition of components during their inspection, noting which are causing the problem and which got affected by it, recommending to replace them in order of priority.

Transparency example in a condensed water service

An HVAC (heating, ventilation, and air conditioning) inspection is the most transparent process to understand if the water coming from the AC is expected. This is because many components surrounding the AC system, internal components, and drainage system can have a say in the issue, indicating problems and culprits.

Let’s read an example of how this kind of inspection helps to service a condensed water situation.

The proof image shows condensed water coming from the air box drain tube during normal air conditioning operations. That is regular on vehicles with a functioning air conditioner system.

A customer dropped off their vehicle upon noticing a puddle of clear liquid underneath it when parked. They thought something was wrong with the cooling system, causing antifreeze to leak onto the ground.

The technician noticed nothing about the customer's concerns on the test drive or the vehicle health inspection.

The mechanic raised the vehicle onto the lift and noticed water on the ground. They traced the water up to the drain hose of the evaporator air box drain. The technician informed the customer that this was normal behavior for this vehicle.

So, the water wasn't leaking because of a faulty part or damaged seal; the droplets were expected per the vehicle's build. In summary, water expelled by air conditioners through the car's underside is ordinary.

Condensation from air conditioner

In this case, there were no "Immediate attention" tags as there were no issues with the vehicle.

Similar Symptoms

Below are just a few examples of typical Symptoms and Fixes your car might be experiencing

Four common causes for a vehicle Leaking Oil and their related parts.

Is Your Car Leaking Water?

The most common causes for water leaking inside a vehicle

Frequently Asked Questions

Is there a puddle of water under your vehicle near the footwell after driving on a hot day with the AC on?

Is the carpet wet from water on the passenger side?

Are there stains around the headliner near the sunroof?

Is there water on your vehicle's dash when it rains?

Do you hear a whistling noise when driving down the road?

Is there a puddle of blue fluid under your vehicle after you use your windshield wiper fluid?

Typical fixes to address the cause(s)

The most common cause: Air conditioning condensation

How exactly does condensation work?

Transparency example in a condensed water service

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