You'll find the heater hoses near the engine's firewall (the wall separating the engine compartment from the passenger compartment). Look for:
* Two hoses relatively close together: One will be the hot hose (carrying hot coolant from the engine to the heater core inside the car) and the other will be the return hose (carrying cooled coolant back to the engine).
* Connections to the heater core: These hoses will connect to the heater core via metal pipes or fittings that go *through* the firewall. You might see these pipes emerging from the firewall near the bottom, closer to the floor.
* Near the thermostat housing: The hot hose often originates near the thermostat housing, as this is where hot coolant is first distributed.
To be more precise: You'll need to consult a repair manual specific to your 1991 Mercury Sable's engine. A Haynes or Chilton manual will have diagrams showing the exact hose routing and locations. You can also sometimes find these diagrams online by searching for "[Your Engine Type] 1991 Mercury Sable heater hose diagram". Replacing them often requires slightly different approaches depending on engine type.
Remember safety first! The coolant system is under pressure when hot, so let the engine cool completely before working on it.
