Water On Passenger Floor Of My Car

water on passenger floorI have just bought an Acura Legend. I just noticed water (moisture) on the passenger side floorboard. Really a lot under the seat area (I ran my fingers across it and it seems to be clear w/o an odor).

It also seems to create fog/moisture on my windows when I am riding with the heater on. Moisture/fog is always on my car windows even when the car is sitting. I guess maybe after driving with the heater on (I never noticed).

Can you tell me what this problem could be? What could cause this? What should I check? Could this be a serious problem?



Hey there Marcus,

I would check the antifreeze level inside the radiator to see if you are low, and to see if there is just clear plain water in the radiator. You could have a heater core leaking antifreeze or in your case maybe just plain water on the passenger floorboard.

Usually the heater leaks up under the carpet under the dash on the passenger side where your feet would be if you extended them as you were sitting in the seat.

When the heater core leaks, it drips antifreeze inside the vehicle (under passenger carpet under the dash) and when you run the heater blower you are just blowing air across the leaking fluid thus producing a sweet like smell out the vents. That smell coming out the vents contains moisture (from the antifreeze leak) which builds up on your windows…producing the film/fog you are witnessing.

I usually take my hand, pull back some of the carpet under the dashboard and run my hand on the carpet, and on the carpet insulation below. Then look and feel my hand, if it feels and looks greasy then its a coolant leak and a leaking heater core.

Heater Core Replacement

If the radiator is full of green antifreeze, you might have a water leak around the windshield weather stripping or the passenger window or sunroof if you have one. I would visit the local manual car wash and have someone sit inside the vehicle as you spray around those areas with the high-pressure sprayer.

Also, if the radiator is full of antifreeze and your hand was not greasy feeling you might have a restriction in the A/C drain. The A/C drains out condensation water from inside the dashboard to outside under the hood on the passenger side via a small rubber hose on the firewall. You can see that a/c water dripping out of the drain around the passenger tire area under the vehicle on a humid day.

When the drain gets clogged with leaves and debris, it backs up inside the cab of the vehicle. The difference between an A/C drain leak and a heater core leak is the A/C water is cold and clear, and the heater leak is warm and greasy feeling.

Cleaning an A/C drain

Please share this with your friends,
Austin Davis

Posted in: A/C and Heating

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