A typical cooling system setup for generator sets and power units with a single radiator and single pump. 

Most Generators and power units will use a typical Single Pump Single Loop setup to cool down the engine. In this setup, coolant is circulated through the engine via a pump typically mounted on the front of the engine. The pump pulls cooled coolant from the radiator into the engine and intercooler. The coolant travels through the intercooler and exits into the oil cooler. After leaving the oil cooler, the coolant is now hot and must travel back to the radiator to get cooled off. The fan pulls in air through the radiator in order to cool the radiator and the hot coolant traveling through it. 

Below is a visual representation of how this system works.