In today’s advanced diesel engines, the cooling system stands at the center of attention. Studies have shown that four out of 10 engine problems are related to improper mixture of coolant and additives or inadequate cooling system maintenance. The cooling system includes many components: radiator, water pump, deareation tank and cap, thermostat, fan and clutch drive, fan shroud, shutters, oil cooler, transmission cooler, belts, pulleys, hoses and clamps, block heater, sensors and switches. These components work in unison to maintain an operating temperature that will allow efficient engine operation.

Unseen dangers lurk
Improperly maintained cooling systems can lead to gradual damage of engine components. The true effects go unseen until costly repairs become necessary. Overheating causes oil to break down, leading to valvetrain problems, while overcooling creates an overfueling condition that can lead to the formation of sludge and acid in the crankcase. Ethylene glycol and propylene glycol are the two most common antifreeze/coolant types in use today. Ethylene glycol is the traditional coolant, whereas propylene glycol is being sold as an extended-life coolant. These two types should never be mixed because their anti-corrosion additives are different. The advantage of propylene glycol is extended service life due to slower depletion of the acid-based additives. Not all engines can use this coolant because it is incompatible with certain metallic and non-metallic materials. Check with the engine manufacturer before use. Coolant is traditionally purchased full- strength in bulk and mixed with tap water. This provides freezing and cooling protection but not necessarily prevention of deposits or corrosion, which can shorten engine life. Corrosion perforates cylinder walls and liners, while deposits plug passages, reducing heat transfer and causing overheating. These conditions promote cavitation and seizing or cracking of engine components. Premixed coolant or coolant mixed with distilled water is recommended. In addition, automotive antifreeze should not be used in diesel engines. Those products contain higher silicate levels that can plug coolant passages. Commercial antifreeze, with a silicate level of 0.10 percent or lower, should be used in diesel engines.

Additives bolster protection
Supplemental coolant additives (SCA) are added to coolant used in diesel engines. SCA provides protection against foaming, scale build-up, acidity, corrosion and cavitation. Maintaining proper levels of SCA can be accomplished with pre-measured, in-line cooling system filters or by adding liquid SCA to the coolant. Levels are monitored with test strips and should be checked at least twice annually. Vehicles under heavy or severe use should be checked approximately every 10,000 miles because high mileage and heavy loads deplete additives more rapidly. Continued monitoring of vehicles’ cooling systems will reduce wear and minimize major repairs or replacements due to extreme engine temperatures.

Jeffrey W. Janka is a senior mechanic for the transportation department at Cleveland Municipal School District.