The EGR cooler on a diesel can be a problem if not serviced on a regular basis. The EGR on your truck serves one purpose, to reduce the production on nitrous oxide that forms in an engine’s cylinders at high temperatures.
To accomplish this, the EGR scavenges a small amount of burnt exhaust gas and directs it back into the engine. This has the effect of lowering the temperatures in the cylinder, below the point that nitrous oxide forms.
Diesels produce a large amount of soot, unlike a gasoline engine. This soot has a tendency to build up on the EGR pintle, in the EGR cooler and the intake manifold. The result is reduced air flow and a EGR pintle that fails to close allowing a continuous flow of exhaust gas into the engine.
The exhaust gas redirected by the EGR is extremely hot and is ineffective in cooling the cylinder temperatures without being cooled. To correct this situation a EGR cooler is installed between the exhaust and intake manifold.
Engine coolant directed through passages in the cooler surround and cools the passing exhaust gas before it enters the intake manifold.
The exhaust gas passing through the cooler is at a much higher temperature and super-heats the small amount of coolant passing through. The coolant then passes from EGR cooler to the oil cooler where once again it is used to cool the oil in the same manner.
The high temperatures produced by the exhaust gas reacts on the engine coolant over time and causes it to gel. The gel plugs the passages in the cooler allowing less coolant to pass. The reduced flow of coolant is now subject to the high temperatures from the EGR flow resulting in higher than normal pressure in the coolant system.
The more the cooler becomes plugged the higher the pressure resulting in a rupture of the EGR cooler. A rupture allows engine coolant to enter the cooling system and the intake manifold as well. Engine coolant is not compressible and if not corrected will cause a blown head gasket, among other problems. This can get quite pricey if left unattended for any length of time.
Remove the intake manifold, EGR cooler and the EGR. Replace the EGR cooler and clean all the soot from the intake manifold and EGR before reinstalling them. The EGR cooler gasket kit makes it possible to replace all the studs, gaskets and seals necessary in this repair. Given the severity of a failed cooler, do not reuse any seals or gaskets once removed.