COOLING SYSTEM.

The radiator rejects engine heat from the coolant to ambient air. Heavy-duty radiators combine a tube-and-fin core with tanks and side plates built to withstand vibration and long duty cycles.

The water pump circulates coolant through the engine block, cylinder head, radiator and coolers. It is belt- or gear-driven, and its bearing and mechanical seal determine service life.

An EGR cooler lowers the temperature of recirculated exhaust gas before it re-enters the intake, reducing NOx formation on Euro 4–6 and EPA-era engines. Hot exhaust passes through tubes surrounded by engine coolant.

An intercooler (charge-air cooler) cools the compressed air from the turbocharger before it enters the engine, increasing air density for better power, fuel economy and lower emissions.

An engine oil cooler transfers heat from the lubricating oil into the engine coolant, keeping oil viscosity and film strength within limits under heavy load. On most heavy-duty diesels it is a stacked-plate or tube-bundle core mounted on the block, with oil and coolant passing through separate sealed channels.