The Vehicle Engine Cooling System Simulation (VECSS) computer code has been developed at the Michigan Technological University to simulate the thermal response of a cooling system for an on-highway heavy duty diesel powered truck under steady and transient operation. In Part 1 of this research, the code development and verification has been presented. The revised and enhanced VECSS (version 8.1) software is capable of simulating in real-time a Freightliner FLD 120 truck with a Detroit Diesel Series 60 engine, Behr McCord radiator, Allied signal / Garrett Automotive charge air cooler and turbocharger, Kysor DST variable speed fan clutch, DDC oil and coolant thermostat. Other cooling system components were run and compared with experimental data provided by Kysor Cooling Systems. The experimental data were collected using the Detroit Diesel Electronic Control's (DDEC) Electronic Control Module (ECM) and the Hewlett Packard (HP) data acquisition system. The engine speed, fuel flow rate and vehicle speed that describe the operating condition of the truck are the main time varying input variables to the code for simulation. Ambient temperature and pressure, relative humidity, and wind velocity are also needed as input. The enhanced VECSS results were validated by comparing the predicted top tank coolant temperature, oil sump temperature, and engine power with corresponding experimental data. The results were compared to three stationary and three transient on-the-road test runs. In general, the predicted responses match well, within 0.5 to 3.5°C (1 to 6°F) of the experimental data, both qualitatively and quantitatively. Intake air temperature generally agreed within 8°C (14°F) between the model and the experimental data. A parametric study was also conducted with ambient temperature as the variable in order to study the performance of the fan and the thermostat.