I have an 04 Tiburon GT and there is some water behind the firewall. It used to drain into the car(not good), but now its not draining at all. Don't know where to find the drain plug to unplug drain.

Is this water or engine coolant? If it's water then the Air conditioning condensate drain may be plugged. Water can also enter if the body sealant has dried out where the firewall meets the body at the A post. If it's engine coolant then the heater core is leaking into the air box.

from under the car , Look on the passenger side, along the firewall for the drain tube,, gently use a wire for a slow prodding of the hose,, the water build up behind the clog will flush it out, and you don't want to jam the clog up more than it is,, a simple push and pull motion should clear it,, but be ready for water to come flowing out

There is a drain hose that allows the water to drain outside the car, it is clogged, jack up the car and support it on the right front, on the right side behind the right tire against the firewall you will see a black hose (it might be tucked in there a little, flashlight is good), use a long bottle brush or a cloths hanger, watch your eyes.

it's usually on the firewall on the passenger side. Short tube pointing downward about 1 inch long. You shuld see water drip out with a/c on and set for outside air, not recirc mode.

It is the condensation from the ac,the drain is stopped up,it is located under the hood,under the ac lines that go into the firewall,look directly below them,it will be there,and there is a elbow boot on the drain,remove it,and blow air into the drain,and if it clears it out,the water will pour out like a water fall,if this was at all helpful,please rate,thank you.

You will need to have the heater/ac box drain hole cleaned out,this drain is located on the firewall coming from the heaterbox, you should see a small hose sticking out of firewall on the pass/side,near the bottom, blow air into it and water will pour out or use a coat hanger and slide into drain hole gentle and water will run out.

If it is clean water then your A/C condensation drain is stopped up and overflowing into the car.If it is coolant then your heater core is leaking and will need replaced.To clean the drain just push a wire or coathanger in and out it a few times or compressed air.You can access it from under the car, it comes out at the bottom of the firewall.

-- open the driver's door
-- locate where the air conditioner blower box is attached to the passenger side of the firewall - see photo #1 - look to the immediate right at the top of the gas pedal arm

-- condensation flows toward the front of the vehicle through the firewall at the leftmost edge of the air conditioner blower box - drain channel
-- open the hood and stand next to the front wheel on the driver's side
-- look down at the firewall over the battery and to the passenger side of the brake master cylinder - see photo #2

-- locate the small diameter metal lines running horizontally and attached to the engine compartment firewall
-- locate the hole in the engine compartment firewall panel behind the small diameter metal brake lines
-- this hole leads to the drain opening in the air conditioner blower box mounted in the passenger compartment
-- follow the brake lines as they run from under the vehicle and turn toward the front wheel on the driver's side
-- locate the hole in the engine compartment panel behind the brake lines
-- insert a short length of stiff wire into the hole through the engine compartment panel to unblock the drain hole

Look on the firewall and under the truck near the firewall -- there's a hose there which let's excess condensation drain out... once you find it, use compressed air to clear it.

The condensation drain is plugged in the heater/AC plenum, the drain is under the hood at the very bottom of the firewall on the passenger side.
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