In order to cope with new regulations and find a better compromise between fuel consumption, pollutant emissions and comfort, thermal management technologies are getting more complex. This is especially true when it requires replacing a basic passive solution with a mechatronic system.A new Active Cooling Thermal-management (ACT) valve concept has been developed to specifically replace wax thermostat while keeping the same packaging and cost range and bringing closed loop temperature control, fast response time and precision. This new module is manufactured by assembling injected thermoplastic components. By essence it leads to dimension tolerances, deformation and wear over its life. Those uncertainties and deviations have to be taken into account when the nominal part is designed to ensure part efficiency till the end of its life.The purpose of this work is to increase the robustness of the design process since the very beginning by developing a multi-physic core model using Matlab/Simscape to describe the actual environment, the function and the aging of the ACT valve. The first part of the paper will describe the mechanical concept of the valve, the modelling philosophy and the development platform. The second part will be focused on the local models of contact and wear. The third part is dedicated to the hydraulic model and the hydro mechanical coupling process. Finally a comparison of the simulation results with experiments will validate the model choices and first results of sensitivity analysis will be shown. In future works, an optimization strategy will be applied and then allow to find the more stable part design fulfilling functional specifications over its lifetime.