EGR Cooler System Overview

The manufacturers of diesel engines have made many changes to meet government guidelines on Nitrogen Oxide (Nox) reduction. Problems posed to the engine and cooling system have not been acceptably addressed, even though the governmental guidelines have been met.

For Nox to form, the cylinder head temperature needs to be high with a rapid ignition and an abundance of air. The purpose of the exhaust gas recirculation (EGR) system is to extract spent exhaust gases and reintroduce them into the engine via the intake manifold. Diluting the air/fuel mixture with exhaust gas from the EGR reduces cylinder head temperature enough to discourage the formation of Nox. The computer opens The EGR at part throttle only on a diesel.

Coolant flows from the water pump through a hose to the oil cooler on the intake manifold. The coolant exits the top of the oil cooler and flows to the passenger side EGR cooler. The cooler appears as a long tube next to the exhaust manifold with the EGR occupying the rear of the tube near the exhaust pickup line. Coolant flows through a metal line with cooling fins used to cool the passing EGR gas before its introduced into the intake manifold.

The problems originate in either the EGR valve or EGR cooler, oil cooler or its screen, intake manifold or gasket. All these problems are associated with increased temperatures.

First and foremost is the problems associated with a failure of the EGR cooler. The small cooling surfaces make it susceptible to blockage due to rust, scale, particulates of various origins as well as sand from the casting of the block. The result is overheating of the coolant, block and oil. A partially blocked cooler is susceptible to flash boiling which could blow the head gasket among other problems.

The oil cooler screen blocks easily due to the increase in oil temperature which produces carbon particulates that bond to make a hard black substance which will clog the oil cooler screen and filter. This results in lowering the oil pressure and causing a bypass of the oil filter.

The oil cooler fractures and allows water into the oil or cylinders or becomes plugged and reduces the oil pressure and flow.

The intake manifold covers the lifter galleys between the cylinder heads it known for blowing seals between the cylinder head and manifold. The intake manifold rests on the top of the engine between the cylinder heads. It has tubes that direct the fuel/air mixture into the cylinders. Water leaking from an intake gasket seal into a cylinder can cause major engine damage.