2005 Elantra leaking under the dash on driver's side

You have to find the leak
Have a shop use their Evap Smoke Machine
Pressurize the cabin & see if smoke comes out
around the windshield,engine compartment,etc
Hate to run hose over the car, but you can see it come
in,so that is an option,with someone under the dash with
a light watching.
Check on internet for the issue on your vehicle
Call an auto glass place, for advice on what they solve

Probably coming out from under the cowling, under the wipers and leaking in side.

Well if it leaks after a heavy rain, then suspect your windshield seal is simply bad and needs resealed.if it is anytime, then it sounds like you have either a heater core leak or a hose to the core.All that is contained under the dash on the passenger side.You will need to take off the plastic covers under the dash on that side then get up under the dash with a flashlight and look while the car is running.Let it get hot and turn the heat on also then just look for the leak.if it is really wet you wont have to wait long with the car running and the heat one to see the leak.

If it smells like antifreeze it's your heater core. If it doesn't smell and you have been using your a/c then it's your condenser or maybe a blocked drain tube. If it's been raining a lot or if you noticed after going threw car wash could be door seals, or even a windshield seal.

A 2010 Elantra?... it's still under warranty. Take it in to the Hyundai Service Dept and have it diagnosed & repaired under warranty.

hi assume this water ? you are saying on floor have you ceck your coolant level? if it is low ? there is a possibility that you may have a leak on either heater hose where it connects to heater matrix or the matrix itself has popped a core and is leaking try feeling if carpet is damp around the heater area under dash ?

Look under the passenger side of the dash, behind the carpet. Feel the back side of the carpet for dampness. If so, try this: In the same area, look for a black rubber hose that comes from the heater plastic box, and pokes thru the firewall. See if it is plugged up. This is the drain pipe for the AC box, and the cowl panel if the side drains are plugged up. Try that, and please get back to me.

if you have air condition,check in the engine compartment on the fire wall under the air condition for a drain hose it may be blocked and that is causing the water to backup and leak inside the car.

I think that I can help you. It sounds like your drain-tube is plugged up. Get in the passenger side, and pull the carpet back from under the glove box. Look for a black rubber pipe that goes from a black box, and pokes thru the firewall, on the passenger side. Remove the hose from the box, and have a container ready to catch water. If water comes out of the black box, your drain hose is plugged up. Clean out the clog, and you will be golden.

The two are of course not related. Check the trunk seal for missing portion, tears, splits, etc. this has to be where the rain is coming in. You can check for leaks with a hose and climb in the trunk with a flashlight, having a trusty helper direct water to one area at a time to check for the leak. The gas cap light is probably on due to a defective evap. vent valve, which is located behind the left rear tire near fill tube for gas tank.