Automatic Transmission Oil Cooler Tube. Engine Coolant Reservoir Hose. Flexible Hose that is part of The Engine Cooling System. Hose A.T.F. Hose Connecting The Expansion Tank to The Cooling System. HVAC Heater Hose. Radiator Coolant Hose. Heater Hose transfers heat from a vehicles Engine to The Heater Core. which warms The Air in The Cabin.