The rising concerns on climate change is accelerating the transition from fossil fuel-based technologies to sustainable energy systems. In this framework, Proton Exchange Membrane Fuel Cells (PEMFCs) are gaining an increasing interest due to their high efficiency and wide range of applications. Nevertheless, these systems experience significant performance losses under high loads, associated with significant heat generation, making thermal management a fundamental design aspect. In this study, a 200-kW low temperature PEMFC was investigated through the development of a 0D – 1D model of a simplified cooling circuit implemented in GT – SUITE environment. The model was used to evaluate the influence of design parameters on the effective efficiency of the system to dissipate the excessive heat. Additionally, a detailed stack-only model, comprehensive of the Membrane Electrode Assembly (MEA) subcomponents, was developed to verify the temperature differences between coolant fluid and membrane. Further, based on the stack-only model results, a temperature-based damage index formulation has been implemented to assess PEMFC performance along 25000 hours of service life. Considering an optimal operating range of the MEA between 60°C and 80°C, the results obtained indicate the need for a radiator capable of dissipating at least 75 kW of thermal power under critical conditions. The start-up phase was identified as particularly challenging, suggesting the implementation of a ramp-up strategy to mitigate the temperature gradient and overshooting before achieving stable conditions by the radiator. With the pump operating at maximum regime (5500 rpm), the stack-only model showed a temperature difference between the membrane and coolant fluid of approximately 2.8°C of the inner cells, while the external cells exhibited higher temperature differences up to 7.4°C, potentially leading to increased thermally induced stress mechanisms. Further, at the end of life (EOL) the single contributions of chemical degradation (83.5%) and thermal gradients (49.0%) were noted to dominate over other thermal aging mechanisms.