Coolant is transferred throughout the cooling system by hoses.
Most vehicles have the engine mounted on flexible mountings to reduce noise and vibration. Since the radiator is mounted to the vehicle body, flexible hoses are needed. Coolant is also carried to the heating system which is usually inside the cabin of the vehicle.
Coolant hoses vary in diameter depending on the volume of coolant that passes through them. Heater hoses carry a smaller volume.
Most hoses are made of rubber, and since they are subject to pressure, they are reinforced with a layer of fabric. They are moulded to a special shape to suit the model and make of vehicle. Some heater coolant hoses also have special shapes. All hoses are subject to hot coolant and high under-bonnet temperatures, and they can deteriorate and fail.