Originally Posted by RAPTOR
I know what your problem is!
This drain line is a smaller diameter hose just poking out of the firewall well below the in/out lines for the heater right? It's there to drain the heater box should the heater core leak. So the coolant doesn't end up in a puddle inside the car. Your heater core is leaking!
The good news - heater cores don't cost too much to replace.
The bad news - you get to them from inside the car, after the whole dash assembly has been removed. Mucho labour $$$.
If you also have aircond that will have to be drained and disconnected as well. How do I know? My XG ute did the same thing, except it wasn't dribbling but rather dropped it's load. The aircond and all the smartlock electrics inside turned me off doing it myself.
To make the car useful until you get it fixed just get a 90 or 180 degree connector (I found one lying around from an irrigation kit that held up for about 8 months until I got the job done). Remove the heater hoses from the firewall and bypass the heater core using the connector (ie. join the hose ends together). Your probably gonna want it fixed before next winter though.
Just to let you know guys. The drain hole is there specifically for draining condensation build up from using the air conditioner. The drain hole unfortunately doesn't stop your floor from getting wet if the heater core leaks. This is because the coolant doesn't build up in that section of the heater box, therefore, regardless, coolant will still drip from your floor vents.
Also if you have a pool of water or dampness on your front carpet it could also be a blocked drain hole. so that when you use the air conditioner, there is nowhere for the build up of condensation to escape. Just for your info. But as RAPTOR said, if you are noticing coolant loss as well, then its most likely the heater core!