The hoses from the heater core don't connect directly to the engine itself. They connect to the
engine's cooling system. Specifically, they usually connect to the
heater hoses that are part of the larger coolant circulation system. These hoses are usually located near the firewall, where the heater core is situated inside the vehicle's passenger compartment.
One hose is a supply line bringing hot coolant *from* the engine, and the other is a return line taking cooled coolant *back* to the engine. The exact location of these connections varies significantly depending on the make, model, and year of the vehicle. A repair manual specific to your car will show you the precise location.
