Water leak on passenger side under the dash

Asked by Dec 02, 2014 at 11:55 PM about the Nissan Truck

Question type: Maintenance & Repair

When it rains, on the passenger side there is a water leak, my vents are clear and the
seal is okay. Not sure what might be the problem.

8 Answers


Most water leaking into the passenger compartment comes from two broad categories. Environmental water (rain) may leak in through flawed sealing systems, and the more common source of leakage, from the heating and air-conditioning system. Water on the right front floorboard, under the passenger’s feet, often comes from the HVAC system. Diagnosis begins with determining the nature of the liquid. A sticky feeling spot, especially if warm to the touch, may suggest engine coolant leaking. A low coolant reservoir sometimes confirms this. Other symptoms may include a sticky film inside the windshield and a sweet odor, like antifreeze in the car. The most likely cause is a leaking heater core. Fresh water on the floor, with no odor or loss of coolant is more often humidity removed by the evaporator. Water from humidity, removed by the air conditioner, is normally drained from the evaporator case. Water seen dripping under the vehicle is from humidity removed by the air conditioner. When the system gets clogged/blocked or constricted/kinked, the condensation water may drip on the carpet and cause problems. A lack of water dripping under the car while the A/C is running could mean debris has plug the evaporator drain then water backs up and overflows into the passenger compartment. Cleaning the drip tube with compressed air will often restore the drainage. After saying all that, IF the floor is only wet after a rain then it is an environmental water leak somewhere around the windshield, roof line, firewall, or door seals. You will have to look for signs - water stains, corrosion, or you can try a non-staining water dye* to locate the leak. * http://www.poolcenter.com/p/party-pool-swimming-pool-color-dye Good luck and I hope someone posts a specific (known) fix to your problem, other than using a whole lot of silicon-sealant...

25 out of 25 people think this is helpful.

Rain leaks in? wash car, clear body drains. have helper look with flashlight. Hang wet carpet up in heated building. Find source of actual water entry during cleaning process. Rinse from the bottom up. When helper starts tapping his flashlight to indicate it is seen, Isolate. Hope this helps too.

7 out of 7 people think this is helpful.

Leaf screens at bottom of windshield can be a problem area. They can allow some types of cowl water entry to increase as weathering changes their shape. Some manufacturers have body service bulletins about these things and have updated parts and procedures available.

7 out of 7 people think this is helpful.

I have a problem with my 2014 Nissan. I think its sealed up like a wiffle ball. Did you get a resolution from anyone?

2 out of 2 people think this is helpful.

The make, model and year with VIN reported to your dealer can allow them to look up any updates or procedure change to fix what may be up with yours. This can be a simple phone call to a fast answer. Cars and trucks that leak weather water from their heater area can get it from the body parts below the wipers ? or the covers that keep the tree debris out. The correct drains for weather water can get stopped up by debris. This is why you handle this with the phonecall first, and perform procedures on your unit based on your actual findings. "the fix is where you find it" Unless theres a bulletin.

3 out of 3 people think this is helpful.

I had rain water leaking onto my passenger floor board and I finally figured out the problem. I removed the passenger side windshield cowl cover and found that the sealing around the cabin air return vent had worn away. This was allowing the rain water to seep into the air return duct and then onto the floor from behind the glove box. sealed the area with some silicone and the leak has stopped. Hope this helps

7 out of 7 people think this is helpful.

1986 720,,,,,,,,,, the water was entering to right floor board due to plugged drainage under the cowl.... remove cowl to find rusted out around the air intake for heater/air into cabin... I used the air hose and shop vac to get the drainage hole open. then I used the sheet rock tape that has holes, placed that everywhere there was a hole. then I used flexable caulking and sealed it up.... then I used metal screen, like for windows and taped it on the underside of the cowl vents using the aluminum tape you use for your furnace ducts. hopefully no more bits of leaves and stuff plugging the water drain vents.. I had to weld in replacement metal on the floor boards as they had rusted out. I then used roofing tar in a caulking tube to spread around the outside of the weld in the wheel well and underside..use latex gloves or just double up a couple bread bags to spread it around... need a few days of 80 degree days for that to set up. so far after 8 mths no more leaks inside passenger floor board.

1 out of 1 people think this is helpful.

I also caulked around the removable plastic cover above the cabin air intake. It was worn and warped which possibly let water into the intake. I called it "air return duct" in my original post but I thinks jacks description is more accurate.

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