Why would water be leaking from under the dashboard on the passenger side of a car?

Answer 1

• If you have air conditioning it's condensation from your AC spilling into your vehicle instead of outside on the ground. It's a clogged line to your air conditioner which has been clogged with debris, leaves and such. A little compressed air should do the trick.
• It might also be a coolant leak from your heater core. It will have a slimy, greasy feel if it's coolant. It will also have a sweet odor. Do not taste - its poisonous.
• Yes, the mysterious water swooshing noise in the dashboard when turning, and/or water leaking under the dash at the passenger side, as well as possibly the heater fan sounding like it's spitting water…there can be only one explanation and this is IT.
• First, let me assure you that all manner of answers from mechanics have been researched and considered, but so far no one has yet answered this satisfactorily in any forum I have come across. Usually it is something along the lines of "coolant leak", evaporator core issues, etc etc but these fellows are missing the vital point…it is WATER not some exotic liquid cocktail usually associated with serious and expensive vehicle problems.
• I own a 1996 Mercury Villager / Nissan Quest which developed this problem after a heavy rainfall. Coincidence? NO WAY!
• I had the proverbial water leak beneath the passenger side dash, as well as what sounded like a bathtub full of water behind my dash swooshing back and forth.
• So here's the deal. These vehicles, like many others have a reservoir above the firewall just beneath the plastic cover at the base of the windshield, which also houses the wiper motor, etc. typically the reservoir collects any water running from the windshield or rain in general. There are two drains one at the drivers side and one at the passenger side. These drains usually work great except when they become plugged with silt, debris from trees shedding leaves, insect matter etc. When this happens, the water simply collects and fills the reservoir with nowhere to go except into the fresh air intake for the cabin heating/cooling system located just above the passenger side glove compartment.
• The water then leaks into the venting ducts and onto the floor. It also stays in the reservoir and sloshes back and forth while driving.
• Any mechanic worth his salt should be able to figure this out and charge you ½ hr labor to remove the plastic shroud and unplug the drains. That's pretty much the extent of it. I did it myself and it took about 20 minutes.
• The wipers have to be removed. There is a release clip at the bottom of the wiper coupling where it meets the drive shaft. Pull it back and lift the wiper straight up and off the shaft. Remove the plastic pins ( they look like slotted screws) along the top of the shroud by turning them 90 degrees and pulling them straight out with some needle nose pliers. Open the hood and remove the rubber seal strip along the edge of the shroud. Find the little plastic holding pins and reach around to the bottom of each pin. You need to compress the little barbs on both sides of the pin to allow it to be pushed up through the hole. There are also 4 plastic push-lock pins holding the bottom edge of the shroud. You will have to pull up on the center (looks like a screw) of each pin and pull it almost all the way out. Then remove the whole pin assembly. A small sharp pair of end cutters works great. Now with a little bit of twisting and careful manipulation you should be able to pull the plastic piece up and out of the way. Start at the corners and pull the piece down and out from under the windshield trim. Then lift it up carefully and move it to rest on the windshield being careful not to disconnect any rubber hoses from the washer nozzles.
• The drains are located at the far edge of the trough in each corner. Use a straightened coat hanger or something similar to poke and clear the drain. Get your garden hose and with a good straight stream of water flush out each drain hole and make sure it is draining. Water will pour out of the rear of each wheel well just under the front of each door.
• Try using a spray of Lysol or other household disinfectant into the trough since it may have had stagnant water for some time. This will kill any bacteria that may have found it a haven for while and ensure that you will not be blowing it into the passenger compartment every time you turn on your blower.
• This happened to me, two huge puddles on my passenger side floor mat twice in one day. I looked up below the dash and found the hole it was dripping from. I found a nearby hose sticking out about two inches that wasn't connected to anything. Reconnected and problem solved. Just a disconnected hose.