Car Leaking Water Underneath Passenger Side

Is your car leaking water underneath passenger side after a car wash or driving under heavy rain? It can be the result of a blocked drain tube, leaked door seal, and damaged gasket. But if your car leak water under the passenger side during summer or while traveling in a humid area, it can cause due to running the air conditioning system.

Water leaking isn’t concerning except for a little bit irritating. However, you can repair the door seal, close the door properly and repair the AC to avoid excessive water leaking under the passenger side. 

Why is my Car Leaking Water underneath Passenger Side?

The common sources of normal water drip under the car’s passenger side are AC drains, sunroof drains, and heater cores. Other potential reasons are faulty seal, defective door seal, or coolant leak. However, you must make sure the liquid leaking under the passenger side is water.

The reason is that coolant or other engine fluid can also leak from the same root that is serious concern and needs different repairs. To determine it, check the liquid using your fingertip. If it’s oily and colored orange or green, its coolant which is more concerning. But if the liquid is only clean water, below are the potential reasons and solutions:

1. Blocked Drain Tube

If you notice water leaking underneath the passenger side and wet the carpet, the water may come from the clogged drain tube. The drain tube runs under the passenger side and is placed behind the carpet where the passenger rests their left foot. The drain tube also runs through the floorboard to the outside of the car to drain water below the car. 

It can be blocked due to debris and prevent water discharge properly. So you can notice water leaking under the passenger side. It can also get cracked and prevent draining water. The drain tube should be visible after pulling the carpet out from the slanted floor. To repair the damaged drain tube, wiggle the tube top of the nozzle. Then use a can of aerosol duster to blow the tube out and clean the nozzle using Q-tip. 

2. Faulty Seal and Gasket

If you notice the water is leaking into the car’s passenger side, particularly after replacing the engine, the faulty seal can be the reason. There is a seal between the car’s body and engine that prevent water from entering the cabin of the car. This seal can leak water inside from the passenger side due to becoming weak or if not installed properly.

Faulty Seal and Gasket

The improperly sealed gasket can’t also prevent moisture from seeping through which can leak water. The water can also enter the cabin through the passenger side due to holes or cracks in the firewall. To fix this problem, make sure all the gaskets and seals are installed properly and are in good condition after replacing the engine. 

3. Air Conditioner

If you are driving a car in a humid area and using the car’s air condition system, you may notice that the vehicle leaking water underneath the passenger side. If so, don’t panic as it’s only the melt-water. When running the car’s AC in a humid area, ice can build up on the pipe that carries AC fluid between the heat exchanger and the compressor. After turning off the vehicle, the ice may start melting slowly and leak under the passenger side. 

The water may also condense in the AC’s heat exchanger that is placed inside the car’s dashboard and may drain away under the car through the passenger side. There is nothing to worry about if water leaks out of the AC during the summer season. In extremely humid climates, your car can leak a steady drip or even a stream of water underneath the passenger side. But if you are worried about it, seek professional help.

4. Defective Door Seal

Your car can also leak water underneath the passenger side due to a faulty door seal. If you experience the problem particularly while driving the car on wet roads, a defective door seal is an obvious reason. To determine this problem, carefully check the place where the car’s door closes against the car’s body.

Car Defective Door Seal

There is a thick rubber gasket running around the opening that prevents rainwater or road splash from entering the car. It also keeps the cars inside dry during the car wash. If the seal gets leaked, water may enter the cabin and drain under the passenger side. If so, you have to replace the leaked door seal to fix the problem.

The sunroof can also get a leak that runs down the pillar. Rarely, some modern car leak water underneath the passenger side due to the floor plan’s faulty grommet or leakage around the mounting belt. In this case, you’ll have to bring the car to an auto repair shop.

5. Header Tank

The exhaust may push out a little water as a result of the fuel’s combustion. So you can notice a wet patch underneath the tailpipe which is pretty normal. But an overheated motor can cause the water steam in the cooling system and small puddles.

If so, you shouldn’t ignore it. You may also notice water under the passenger side of water in the system overflow. Water can also overflow from the header tank. When the car reaches the operating temperature, the water will overflow through a hose to the passenger side.

6. Crack Windshield Seal

Water may also leak inside the vehicle on the passenger side and run down on the carpet due to cracked water. It’s particularly true if the car leak water after a car wash or driving under heavy rain.

Crack Windshield Seal

The windshield seal can crack down due to accident or rough use. However, you can experience the same consequences due to door seals, closing the door inaccurately, or blockage of the AC. So it needs deep inspection.

Should you be Worried if Car Leak Water underneath the Passenger Side?

No, water leaking is not a major concern. Since it can cause due to AC, damaged rubber seal, and exhaust condensation, it won’t impact the performance of your car. However, whether you should concern or not is depend on the cause of the water leaking under the passenger side. If your car leak water due to running the AC during summer or in a humid area, don’t worry.

It’s also okay if you notice some water under the passenger side after a car wash or driving under heavy rain. Simply check the door seal and gasket and replace them if required.

But if the leaking water is the result of clogged drain water or a cracked windshield, it can be risky and irritating to drive. In this case, bring the car to the nearest auto repair shop and fix the issue. Otherwise, excess water under the passenger side can cause corrosion or mold buildup.

Fixing Cost of Water Leakage under Passenger Side

In most cases, you won’t have to break the bank to fix the water leak problem. But if you need to replace the AC evaporator to fix the water leakage, it can cost about $1000.

Fixing Cost of Water Leakage under Passenger Side

The other expensive repair is repairing the car’s window and door and replacing the heater core which can cost $500 and $1200 respectively. But in most cases, you may only need to repair the rubber seal which won’t cost more than a hundred dollars.


Is water leaking from the car AC normal?

It’s normal if your AC leak water outside the vehicle. But if the water leak inside the vehicle after turning on the AC and if it’s too much water, don’t take it lightly. Instead, consult with an expert mechanic. 

Why is my car leaking water under it when parked?

You may notice water leaking under it after parked; it can be the result of the condensation of your car’s AC system. If your car’s air conditioning system produces condensation, the water will start dripping and forming a puddle that you’ll notice near the engine housing. 

Why is the car leak water from the front?

Your car may leak water from the front due to an overheated motor or excessive water in the cooling system. A faulty radiator cap or loose hose can also cause water to leak from the front of a vehicle. 

Final Words

If your car leaking water underneath the passenger side, don’t panic. Instead, troubleshoot the underlying source that causing water leakage. Above all, make sure your car leaking water as it isn’t concerning at all.

But if your car leaks oily or green coolant or engine fluid, consult with a professional mechanic immediately. The reason is that it can be the result of some serious concerns like tank leakage, insufficient fluid, or engine damage.

My name is Tom Vanderbilt. I am an automotive expert and renowned for my profound knowledge of automobiles. I have made significant contributions to the industry through my experience and expertise. I have a natural curiosity and fascination for cars. My journey is to explore the intricate dynamics between people, their vehicles, and the ever-evolving transportation landscape.

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