This paper deals with engine evaporative cooling on the VW TDI diesel engine at high heat rejection running points. Engine tests and thermohydraulic 3D computations inside the engine head are used. First, the basic engine is studied. Then, the flow rate corresponding to evaporation is determined. Around this flow rate, the influence of inlet coolant temperature and circuit pressure are studied. The engine tests and 3D calculations give hydraulic ways of improvements consisting in balancing the flows around the different cylinders. Geometrical modifications of the inside engine circuit (gasket....) are then tested to achieve these improvements.