I have a 2008 Toyota Kluger and have a water leak under the dash. It seems to be worse going around a right hand turn or round about. I can hear it splashing.
I think it might be the heater but could be a build up of condensation from the air con I guess.
If it's just water you are getting from under the dash, then it is most likely the drain for the AC/heater box is blocked up. When you run the AC, condensation forms on the evaporator and builds up in the box. Since the drain isn't working, it builds up until it spills over into the passenger compartment. To fix this, get a long, stiff piece of wire. Jack up the front end of the car and place on jack stands. Locate the drain tube which should be on the passenger side of the vehicle near the firewall at the back of the engine compartment. It will be a rubber tube just hanging out in the breeze, but probably not below the level of the bottom of the vehicle. Take your wire and insert it into the tube and run it up the tube ... this could take anywhere from a foot to two feet of wire (say 2/3 of a meter). You'll know when the blockage is clear, because you'll probably get a face full of water out of the tube.
If you have anti-freeze coming into the compartment, you have a leak in the heater core and it would need to be replaced.
