With the new EPA regulations requiring an EGR cooler installation into all diesel vehicles, it’s important to A) know what an EGR cooler is, and B) know how it works and how to keep it working. Let’s take a 6.4L engine; a pretty good sized diesel engine at that. The EGR circuit that houses the EGR would also have the cooler running in the same circuit.
As the EGR pulls the exhaust emissions back into the engine through itself, the emissions have to go through the cooler first. The cooler does exactly as its name implies; it cools. The cooled exhaust acts as an additional way to cool the combustion chambers inside the engine, producing less exhaust because the efforts of the engine are less from being cooled. So the process continues until the truck is turned off ad started again the next day.
In a 6.4L powerstroke engine, the engine is already working overtime. The recirculated and cooled exhaust comes back through and slows down the strokes of the engine, even when the engine is still working to keep the truck up to the current speed. The EGR cooler never fully shuts off, but continues to work hard to keep the combustion chambers from exploding because of excess heat. It’s important that a diesel combustion engine doesn’t overheat because then it produces too much NOx emissions for the EGR to filter.