Where is the heater core in the Subaru legacy wagon when there is a leak on the floor?

The heater core is found on the passenger side, up under the dash. To remove it is quite a mission but do-able. You will need to remove the dashboard including disconnecting a lot of the wiring looms (take digital pictures before you start and during so you can get it all back together again) You will also need to unbolt the steering assembly although it can stay connected. I did mine but it took a few calls to my mate (a Subaru mechanic) to get it all sorted. You obviously can't drive the car once you start so make sure you have alternate transport sorted. One final word of warning - when you are looking at the wiring don't get too excited when you see some disconnected wires when you stick your head under the dash. They are only connected when you want to get fault readings from the motor or to reset the computer. So the photos of what was connected will help a lot. If you think you want to do it then the starting point is the centre console armrest. this gives you access to the other bolts holding on the centre console which you need to remove to get the stereo out and so on and so on. Hope this helps

Take your time and take photos :)