Why Is My Car Leaking Water? 15 Common Causes

Reasons behind a car leaking water include AC and exhaust condensation, obstructed drain channels, and issues with the windshield washer system and evaporator core. Especially during the rainy season or even winter, ensuring your vehicle cabin is kept dry and comfortable is of the essence. Otherwise, you may have to bear with damp seats and flooring (not to mention anxiety) when traveling.

This article will go over 15 of the most prevalent causes of a car leaking water:

1. Clogged cowl or drain plugs
2. AC system or exhaust condensation
3. Debris or any obstruction in the drain hose
4. Issues with the windshield washer system
5. Old or dilapidated weather stripping
6. Puckered, distorted, or leaking seals
7. Aging sunroof drains
8. Plugged muffler drains
9. Broken condensate drain pan
10. Loose hinges and disengaged latches
11. Damaged door membrane or seals
12. Overfilled header tank
13. Dirty evaporator coils
14. Ambient temperature
15. Physical damage

This non-exhaustive list aptly covers the top reasons behind water leaking from cars. Additionally, this entire guide aims to familiarize you with each and get you up to speed on how to best address the issue.

Many of the items here involve inspecting your vehicle components and replacing worn parts as needed, while others require the expertise of a licensed mechanic or technician.

Without further ado, let’s delve into the causes of those water leaks!

Why Is My Car Leaking Water?

1. Clogged Cowl or Drain Plugs

The main answer to the question, “Why is my car dripping water?” is problems with the windshield/wiper cowl or drain plugs (a.k.a. cowl leak). The components mentioned above are two of the many parts of your vehicle’s drain system.

The cowl protects your windshield wiper system and cabin filter area from foreign elements. It is located at the base of the windshield (where wiper linkages park) and is usually covered by a slotted metal or plastic cover connecting to drain channels.

The drain plugs are situated on each side of the car (just behind the front wheels on most vehicles), where water from the windshield cowl exit. Jeep Wranglers can have up to four drain plugs.

Leaves, acorns, debris, and increment weather are the main causes of a cowl leak. The first three can get stuck in the cowl slots and eventually sucked into the cabin filter (view on Amazon) and drain lines, resulting in a clog. Meanwhile, the third can speed up rust formation and lead to worn cowling seals and cowl holes draining water into the engine.

To prevent the cowl and drain plugs from getting plugged, regularly inspect them for holes, obstructions, or early signs of corrosion. Make sure to include the heater core area in your inspection. Use sandpaper and a wire brush to remove any visible rust. And apply a rust converter or rust encapsulator on affected areas to stop corrosion from spreading.

For extremely clogged cowls, clean them by first removing larger objects. Next, use a leaf blower or air compressor to eliminate smaller debris in the cowl, cowl drains, and air ducts. While at it, blow out areas around the hood of your car where dirt collects, like the grille and fenders.

2. AC System or Exhaust Condensation

Another reason for water leaks or puddles from under a vehicle is condensation from your exhaust or AC unit. In some cases, these water leaks can be seen by the rear of the engine bay. AC condensation is primarily the reason behind those surprise puddles (particularly when water drips under your car when the AC is on). But if your air conditioning is off, the exhaust is the next likely culprit.

Either type of condensation should not really be a cause for concern. However, spotting large clouds of white condensation from the tailpipe should be. Seeing this symptom suggests the presence of coolant in the vehicle’s combustion chambers, which, in turn, means that you may have a damaged head gasket.

Blown head gaskets aside, you can reduce the occurrence of your car AC leaking water by using the AC unit’s recirculation setting instead of its fresh air option. Doing so ensures you do not bring fresh air containing more moisture inside your car cabin. This will also prompt you to keep your vehicle’s interior always smelling fresh since you will recycle the air inside every time you turn on the AC.

3. Debris or Any Obstruction in the Drain Hose

If your car drips water inside and when AC is on, the problem source could be obstructed drain tubes in your vehicle’s air conditioning system. When drain tubes get clogged, the AC condensation gets pooled within the AC box, resulting in the car leaking water on the passenger side (into the floor) or some other area inside the vehicle.

This incident would be hard not to notice, as it is characterized by a dank in-cabin smell (similar to when wet laundry stays inside the washing machine for a day too long).

4. Issues With the Windshield Washer System

Your vehicle’s windshield washer system is what you activate to improve on-road visibility. Its reservoir is usually located under multiple engine components, with fill tubes easily accessible from the passenger or driver side.

Under ideal circumstances, this system is not prone to wear as its parts are made of durable, high-grade plastic. But when the windshield washer reservoir breaks, you may notice water leaking from under your car.

There are only two things that will cause the reservoir to break. One is an on-road accident, and the other is a user error. Some car owners erroneously fill the reservoir with water instead of washer fluid. This is a costly mistake (especially during winter) since the frozen water inside causes the reservoir plastic to harden and crack when it thaws. And you know what will happen next — car water leaks (or fluid leaks, for that matter) will occur.

5. Old or Dilapidated Weather Stripping

Weather stripping is that small band of rubber that rests against your side windows and windshield and prevents water ingress inside and out. But if it is not flush with the glass, water could seep through the spaces, run through the car door or windshield, and into your vehicle cabin.

Spots to watch out for leaks in your vehicle are your car doors, dashboard, and trunk. Water leaks are often the case for old weather stripping but could also result from new weather stripping that has been incorrectly installed.

6. Puckered, Distorted, or Leaking Seals

Like your windows and windshield, other areas of your vehicle, such as top covers, flare holes, and cowl side panel, also come with seals. If these seals are damaged or punctured in any way, water leaks will inevitably happen. Age is the #1 cause of leaking seals. But accumulated dirt, debris, and even engine vibration are also part of its list of culprits.

7. Aging Sunroof Drains

Sunroofs would arguably be the most common cause of water leaks if all vehicles had them. Sunroofs (or any other type of moveable roof glass) are best kept in free-flowing condition, lest you will be welcomed with a cold morning shower on your way to work.

Sure, this feature has water-collection trays around the perimeter of its opening. But if these trays get plugged with leaves, tree droppings, or other forms of obstruction, water will not be able to reach the small-diameter hoses and travel down the lower drains in the undercarriage.

Pour some water into the corner trays to keep sunroof drains in tip-top shape. Similarly, treat stubborn clogs with a mild shot of compressed air alongside a small stream of water. Never try to clean these trays by poking them with a sharp object, as their rubber tubes are easily punctured.

8. Plugged Muffler Drains

This small hole drilled at the rear face of a muffler is not necessarily a standard feature in cars. It only applies to vehicles with “less water flow in their exhaust systems due to mounting and under-carriage configuration constraints.” It is meant to help with normal exhaust condensation. But if it gets plugged with grit buildup, it could leak water from under the vehicle.

Muffler drains will require your attention if you use your vehicle mainly for off-roading. And even if you do not, you would still have to inspect them regularly as water pooling in these drains can exacerbate corrosion of your exhaust. If you’re unsure whether your vehicle has this fixture or not, consult your oil-change provider or local mechanic to have them check your car’s muffler.

9. Broken Condensate Drain Pan

A damaged condensate drain pan is not something that happens overnight — it starts with a simple clog. When left unattended, more dust and dirt accumulate over time, resulting in a severely inhibited flow through the drain line. Initially, this leads to anecdotal water leaks from the vehicle’s AC.

But if the leaks happen more frequently, the dirt buildup on the drain pan produces more rust and algae, ultimately damaging the component and resulting in repeated episodes of your car leaking water. You can end this vicious cycle by cleaning the condensate drain pan and having it repaired or replaced as needed.

10. Loose Hinges and Disengaged Latches

Tight-fit hinges and latches are especially crucial for vehicles with removal tube doors and interchangeable hard and soft top covers (view on Amazon) — to name a few. When these parts become loose, they allow water outside the car to enter the cabin.

This may not be important during summer and drier seasons, but it would cause significant inconvenience when driving during winter or in inclement weather. Not only are they likely causes of water leaks but also hard-to-breathe air and unpleasant, dank smells inside your vehicle.

11. Damaged Door Membrane or Seals

Most cars have rubber seals lining the edge of the doors and a membrane inside. These fixtures keep the vehicle doors waterproof, permitting water to only drain out of holes in the door and outside of the cabin. However, there are instances when they could either be installed incorrectly or damaged.

If you notice water accumulation in the passenger footwell, inspect if your door membrane is peeling away. Similarly, regularly examine your door seals to ensure the rubber is not frail or brittle. Otherwise, get those seals immediately replaced.

12. Overfilled Header Tank

A header tank is a liquid container inside your vehicle positioned higher than the main tank. It has a feed from the bottom, is unpressurized, and relies on the radiator cap to decrease pressure and allow liquid passage.

A header tank is designed to accommodate the extra volume of water that materializes when a vehicle reaches normal operating temperature. So if it gets overfilled with water when the car is cool, it is expected for heated water to overflow through the overflow hose, creating a water leak.

13. Dirty Evaporator Coils

Evaporator coils like ACDelco 15-63852 Auxiliary Air Conditioning Evaporator Core (view on Amazon) not only impact your AC unit’s ability to function effectively but also result in your car dripping water. And the reason for both is the same — clogged, dirty evaporator coils. If an evaporator coil becomes coated with dirt, water can no longer coat its surface and ends up dripping to the floor.

This situation is made worse when the condensate drain pans are clogged with mold, dirt, or insects or become rusted. Fortunately, cleaning the evaporator coils is no rocket science. Easy-to-follow steps are detailed in this other article.

14. Ambient Temperature

Different weather conditions can lead to your car leaking water. For instance, your car exhaust tends to produce more condensation on colder days. Conversely, running the AC unit of your vehicle in humid climates can cause a steady drip or even a stream of water condensation.

Both scenarios should not be too much of a cause for concern, as exhaust condensation immediately clears up after warming the muffler or driving around for a while.

15. Physical Damage

If all other components check out, then physical damage to your vehicle may be the cause of your car leaking water inside. It could be a leak in the water pump, a hole in the coolant reservoir, or something more serious. In this situation, however, you would likely notice your car leaking water only when it rains or after prolonged exposure to moisture.

The reason behind this conditional leak is that the water is coming from an external source. Hence, water would only get a chance to seep through cracks and crevices during inclement weather if pressurized water was applied to the vehicle (typically in a car wash) or if the car was parked by a sprinkler.

For all these causes, confirm if the water dripping under your car is, in fact, water. This step may seem ridiculous, but it is necessary since H2O is not the only thing that could leak from your car. You may have a coolant or oil leakage.

To rule other substances out, first look for density, smell, and color distinctions. You may rule out whether the substance is oil-based or not by touching it. However, this may prove tricky if your vehicle is on a dark and uneven surface like a parking lot or asphalt driveway.

Fluid Color

The same can be said when determining the color of the mixture — which is why it is best to dab a piece of paper or an old cloth in the puddle or collect it in a pan to take a closer look. For reference, here is a color guide that will give you an idea of what kind of fluid you are dealing with (or if it is just plain water):

Color	Fluid
Dark Brown	Brake fluid or older engine oil
Light Brown	Newer engine oil or gear lubricant
Red, Pink	Transmission or power steering fluid
Orange	Transmission fluid or radiator coolant
Yellow	Radiator coolant
Green	Antifreeze from water pump, hoses, radiator, or windshield wiper fluid
Blue	Windshield wiper fluid

Coolant usually has a yellow, blue, or green hue with a sweetish smell and is relatively easy to differentiate from a water leak. You may have trouble distinguishing them if your car’s cooling system uses pure water or if you mistakenly put H2O into the coolant chamber. Either way, take your vehicle to a local mechanic immediately.

Water Leaking From Car and Overheating

If you experience your car leaking water while overheating, it could be an indication of a potential engine issue. In that case, have your car towed to the nearest repair shop.

Conclusion – 15 Reasons My Car Leaks Water

In summary, here are the most common causes of water leaks in your vehicle:

1. Clogged cowl or drain plugs
2. AC system or exhaust condensation
3. Debris or any obstruction in the drain hose
4. Issues with the windshield washer system
5. Old or dilapidated weather stripping
6. Puckered, distorted, or leaking seals
7. Aging sunroof drains
8. Plugged muffler drains
9. Broken condensate drain pan
10. Loose hinges and disengaged latches
11. Damaged door membrane or seals
12. Overfilled header tank
13. Dirty evaporator coils
14. Ambient temperature
15. Physical damage

Barring complications, your car leaking water proves that your car systems are working and should be considered harmless. But if the leaks become more than a patch of water on the ground, you should immediately exercise due diligence and check the condition of relevant engine and HVAC components.

Furthermore, consider other symptoms accompanying these water leaks, as they may indicate more serious vehicular problems.