:The objective of this study was to determine the effects of vehicle front end components on engine compartment air flow. Isothermal road tests were conducted on a 1989, four door sedan car having a 3.0 liter V-6 engine and an automatic transmission. The vehicle under study had a combined grille area of 0.1194 square meters. The engine occupied approximately 35% of the under hood plan view area.The air velocities measured at the radiator exit section (between the radiator and the fan shroud) were the data of interest. No coolant was circulating in the OE radiator or heater core, and no refrigerant was flowing in the OE condenser or evaporator. However, constant air temperature runs were accomplished by having a remote radiator installed at the rear of the vehicle for engine cooling during the tests.The road test data for the “Fan Off” condition showed that the total available air flow (as measured by air velocity exiting the radiator) was reduced: (a) 48% by the underhood air conditioning and engine cooling components; and (b) 36% by the vehicle front end components, thus resulting in a total air flow reduction of 84%.The road test data for the “Fan On” condition showed the fan, motor and shroud assembly to be effective in improving engine compartment air flow up to a vehicle speed of 96km/hr.Any improvements in the design and installation of the underhood HVAC and Engine Cooling components would result in improving engine compartment air flow.For verification of test results and instrumentation used, the road air flow data was correlated with the component wind tunnel data.