EGR cooler and engine failures on the 6.0L Power Stroke can often be traced to a chain reaction that starts with the Engine Oil Cooler failure. The engine oil cooler has small narrow, flat cooling tubes that are easily clogged by foreign material in the coolant. Engine coolant flows through the engine oil cooler first and then to the EGR cooler. So if the engine oil cooler becomes clogged, then engine oil may become overheated causing poor performance and eventually engine damage. The restricted downstream flow of coolant will also cause coolant within the EGR cooler to flash-boil and spill coolant into the overflow tank. Eventually the overflow tank overfills, coolant is lost and the engine will overheat. In time, the EGR Cooler can also become corroded under these conditions, and will leak coolant into the engine oil.