The need to improve the engine performance and fuel consumption subject to ever more stringent emission standard spar the interest in the aspects of understanding and quantifying the thermal behavior of engine components and systems. Considering these points during the design of the vehicle thermal management system based on test would consume far too many resources. Fortunately, the simulation tools have become more prominent in the pre-prototype phase of the vehicle development process and they had reached a mature stage; where they can contribute successfully to a significant extend to meet the vehicle development targets.In this work, a methodology to model the Vehicle Thermal Management System (VTMS) in order to understand and quantify its behavior has been developed. The partial systems under consideration are: the gas circuit, the cooling circuit, the lubrication circuit and the thermal capacitance of the engine structure under the vehicle driving conditions. The results obtained by using the integrated VTM sub-systems tools are in a good agreement with the measurements. The integrated system has been used to study the thermal transient behavior of the vehicle under a given driving cycle (e.g. European Transient test Cycle, ETC). Due to the dramatic increase in the computer performance today, one can say that the computing time of the global system based on the 1-D simulation tools is possible.