Your heater valve is whats leaking. It is the red vacuum hose, it goes just inside the dash on the passenger side. You will have to remove the right side plastic screen for the venalation inlet. The valve is spring loaded, and reverts to full hot when goes bad. You can test it using a vacuum gauge, it gets its source from the drivers side, it is the white vacuum line going into the cabin, and it splits right at the firewall, pull the red vacumm line off and see if it hold vacuum.