As part of global efforts to reduce greenhouse gas emissions, the automotive industry is moving towards the electrification of its fleet – including full electric and hybrid vehicles. Considering hybrid vehicles, the energy efficiency and thermal management of powertrains including IC engines remains an important contribution. In this regard, engineers need accurate tools to understand heat-transfer in engine bays. This work presents a flexible test rig design to be used for the validation of CFD simulations of an underhood environment. The test rig and measurement equipment are introduced in detail with experimental data (and CAD) being available. A possible test scenario presented in this research is when an engine is subjected to heavy loads (i.e., constant uphill driving) and the vehicle is subsequently stopped. The experimental results are analysed and, furthermore, the data in terms of flow and temperature fields is compared against the results of the numerical simulations. This sort of comparison is the main usage scenario for the constructed rig, and it demonstrates the value of this facility for research. The rig's geometry and the experimental data being available can additionally be used to facilitate development and validation of various CAE methodology as well as simulation techniques.