There is no fix other than a heater core replacement.
There are a couple of ways to do this, ranging from a full dashboard removal, to adventures in cutting the heating/cooling "plenum".
See "Related Questions" below for both and tons of real-world tips and tricks and sage advice.
Heater core.
Right side
Do you mean that your heater core is leaking coolant ? That would mean that the heater core is clogged. The heater core is like a mini-rad, if it is clogged it leaks.AnswerNo, there is not an overflow tube/outlet on the heater core.See "Related Questions" below for more about Taurus / Sable heating/cooling systems.
the heater core, heater core hoses or heater control valve is leaking
If "heater coil" is just another term for "Heater core", then yes, most all cars have them.See "Related Questions" below for tons of information about Taurus / Sable heater cores.
If it is leaking inside the car, the heater core has failed.If it is leaking inside the car, the heater core has failed.
roof or heater core leaking roof or heater core leaking
A leaking heater core will cause the engine to overheat because the coolant is leaking out.
The heater hose connection is fully inside the engine compartment - so if you have leakage inside the car, chances are extremely high the core has sprung a leak. See "Related Questions" below for more
Leaking heater core.Leaking heater core.
heater core is leaking.
Heater core leaking.