Expansion tank to thermostat housing to heater core hose. 1 per car. As an engine heats up, the coolant expands and impacts the coolant system, hot coolant needs to flow from the top of the radiator to the expansion/recovery tank. The cooling system keeps the engine at a constant temperature to avoid overheating and potential damage the engine seals and lubricants. The engine coolant recovery tank hose allows coolant to circulate back and forth between the vehicle’s radiator and recovery tank for temperature and pressure regulation. It’s important that this hose is in good shape and not squishy to the touch, or you may be in danger of a failure resulting in a breakdown.
