Cooling systems maintain coolant temperature within operating range to prevent engine from heating. In a water-cooled engine, the cooling system is comprised of: Radiators, thermostats, fans, oil coolers, connecting tubes and pipes and the cooling water. Coolant from the bottom side of the radiator passes through oil cooler, enters cylinder block, flows around liners to remove heat, up to cylinder head, and then back to the radiator through the thermostat. A closed cycle meant to maintain perfect engine operation. Always use genuine replacement parts!