Hydraulic EGR valve open (Photo credit: Wikipedia)
The EGR cooler is one of several problems encountered on diesel engines, especially the Ford 6.0 liter. Diesel engines, unlike gas engines, produce an enormous amount of soot through engine combustion.
EGR Cooler Function
Diesel engines provide superior fuel economy and longevity when compared to gas engines, but do require more service. The EGR or exhaust gas recirculation valve and cooler direct a small amount of spent exhaust gas from the exhaust system back into the engine cylinders to reduce cylinder head temperatures.
High combustion temperatures cause oxides of nitrogen (NOX) to form and expel into the atmosphere. NOX are harmful to the environment and add to the greenhouse effect. The spent exhaust gas temperature is lower than the combustion temperature and therefore, when introduced into the cylinder at the time of combustion, lowers the combustion temperature and prevents the formation of NOX.
EGR Cooler Description
The EGR cooler is a long cylinder on the passenger-side cylinder head. There is a metal pipe extending from the exhaust manifold to the cooler from which it picks up the exhaust gas. A computer operated EGR valve opens and closes to regulate the amount of exhaust gas entering the intake manifold.
The inside of the EGR cooler has a radiator core similar to the large engine coolant radiator in the front of the truck. Coolant passes through the oil cooler near the oil filter to cool the oil enters the EGR cooler and then returns to the radiator. Exhaust gas passes over and around the radiator core in the cooler that lowers the temperature of the exhaust gas. The exhaust gas temperature must be lower than the combustion temperature to be effective in reducing combustion temperatures. When the exhaust enters the cooler it is around 1500-degrees.
The designing of the cooler radiator element is the problem and remains unsolved satisfactorily. The holes in the core are to small and collect carbon from the exhaust, sand from the casting process in production of the engine and scale from the coolant. If that is not enough, it can not withstand 1500-degree heat continuously. They always fail-its just a matter of time.
Consequences of Cooler Failures
A crack developing in the EGR cooler core is common. The exhaust gas pressure within the cooler averages as much as 50-PSI. Exhaust gas enters the coolant system through the crack and raises the temperature of the coolant and the oil. Radiators are designed to hold 12 too 17-PSI, so the extra pressure blows the coolant out of the radiator through the overflow tank.
This results in the engine overheating causing a head gasket failure, cracks in the valve seats and the overheated oil causes havoc with the bearings. The increased temperature of the coolant causes the coolant to transform to sludge and further blocks the cooler, and worse, the oil cooler preventing oil flow. It’s an absolute domino effect with catastrophic results.
If coolant from the cooler core enters the intake in sufficient quantity, it will enter the cylinders. Coolant is not compressible and will cause a bent rod or broken piston.
Cleaning the EGR Cooler
There are kits at your local auto parts stores that contain three types of cleaners. They are designed to be sprayed into the intake manifold to rid it of coking, a radiator flush to clean the EGR cooler and a can of injector cleaner to be poured into the fuel tank. Accomplish this every 15,000 miles.
Given the inevitable, this may or may not extend the useful life of the cooler slightly. The best procedure is to purchase an after-market cooler that is bullet-proof. Instead of a heater core construction, it uses pipes with large openings on the inside of the cooler. They will not crack or block up. You can easily replace the cooler on your own with very little experience in two or three hours with common tools.
Read articles on the 6.0 liter engine and perform the proper preventative maintenance in a timely manner using the proper oil and filters. Replace the EGR cooler with the upgrade and use the cleaning kits regularly to remove the coke from the intake manifold and the engine will run trouble free much longer. All of the above EGR cooler failures are over $3000 to repair at the Dealer.