This paper describes multi-resolution, distributed design and simulation software for rapid prototyping and analysis of complex systems using a Co-simulation approach. The current focus of this work is on the modeling of the engine cooling system in the Ford Escape Hybrid SUV vehicle. In that particular vehicle the cooling system consists of three coupled subsystems: a) engine cooling; b) electronic transaxle cooling; and battery cooling. This paper discusses two aspects of this work: a) high level description of the developed models and co-simulation approaches; and b) comparison of co-simulation to test data. Most of the model predictions deviated from the test data by less than 5%. Results indicate that distributed multi-resolution simulations can significantly accelerate the analysis of flow-thermal processes in complex vehicle systems. Moreover, the approach allows coupling of different codes with different functionalities to obtain integrated results not possible with any one individual code.