The Tatra 815 is a heavy-duty truck equipped with the T3-930-51 air-cooled V12 diesel engine, designed for both road and off-road applications. This study focuses on the engine’s cooling system, which relies on airflow regulation to maintain optimal operating temperatures. A 2D numerical simulation using Ansys Fluent was conducted to analyze air-flow distribution and heat dissipation among the cylinders. The simulation was done at a cross-section through the motor's cylinders at a 90° angle. An experimental measurement was performed to gain an intake air velocity, which served as input data for the simulation. Results showed that airflow distribution was relatively uniform, but overheating in cylinders 6 and 12 likely results from overall engine temperature rather than localized cooling inefficiencies. The study suggests that airflow is not the primary cause of overheating. Future research will include 3D numerical simulations to better understand airflow behavior, heat transfer, and potential improvements in the cooling system design.