Engine failure may arise for a number of reasons. Finding the reason for the problem is essential in order to prevent future breakdowns. According to Bill Mirth, North American heavy-duty sales manager with the FP Diesel brand of Federal-Mogul Corp., if a piston is found to be at fault, it is critical to find out what caused the piston to fail.
"It's important to understand that very few pistons actually fail," says Mirth. "In truth, they are damaged by a faulty operating environment. These conditions commonly include lack of lubrication, abnormal combustion, the presence of debris within the engine, clearance issues that lead to physical contact between the piston and another part and operational issues such as over-reving (sic) or overloading the engine or improper shutdown."
The life of a piston is directly related to its environment. "As a result, virtually all situations resulting in damage to a piston can be traced to an issue unrelated to the construction and quality of the piston itself," says Mirth. "In other words, the worst thing a technician can do is simply assume the piston was at fault and ignore the actual cause of the damage. In that case, he's just throwing parts at the problem, which invariably leads to additional issues."
Jay Wagner, heavy-duty brand manager with Clevite Engine Parts, cites fueling problems as another cause of piston failure. "If the engine injection system is delivering the wrong amount of fuel, at the wrong time or for the wrong duration and with a poor spray pattern, this can result in excessive heat, erosion or a washing of the cylinder walls with fuel, "explains Wagner.
In order to prevent heat build-up that can lead to piston damage, it is important the correct level of lubrication reaches the piston at the skirt and piston pin. Wagner advises technicians to examine piston oilers. "Many of these are very delicate in relationship to other parts of the engine and are bumped easily, resulting in either a broken of improperly directed oiler," he says.
Contamination wreaks havoc on pistons, too. Water contamination causes erosion and fuel and lubricant dilution. "Contamination can be water, fuel, particulates from the air intake or foreign objects," says Wagner. "Particulates can wear the ring lands, resulting in increased oil consumption. Foreign matter can be anything including nuts, bolts, valve train or turbocharger parts, and much of the time foreign matter in the combustion chamber is the result of another component failing."
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