Presented are results from numerical investigations of buoyancy driven flow in a simplified representation of an engine bay. A main motivation for this study is the necessity for a valid correlation of results from numerical methods and procedures with physical measurements in order to evaluate the accuracy and feasibility of the available numerical tools for prediction of natural convection. This analysis is based on previously performed PIV and temperature measurements in a controlled physical setup, which reproduced thermal soak conditions in the engine compartment as they occur for a vehicle parked in a quiescent ambient after sustaining high thermal loads. Thermal soak is an important phenomenon in the engine bay primarily driven by natural convection and radiation after there had been a high power demand on the engine. With the cooling fan turned off and in quiescent environment, buoyancy driven convection and radiation are the dominating modes of heat transfer. The unsteady and turbulent nature of this complex phenomenon requires high spatial and temporal resolutions and an effective computational strategy. A CFD procedure for modeling buoyancy driven flow in vehicle underhood is demonstrated. Computed temperature and velocity of air under the enclosure are compared with experimental data at a number of different locations in the control volume. The numerical results exhibit satisfactory consistency with measured values.