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Cooling Systems

The Cooling System Provides Total Engine Temperature Control
The cooling system is designed to:
• Absorb heat from engine components
• Circulate coolant in the engine
• Dissipate heat through the radiator
• Control coolant and engine temperature with the thermostat

The coolant absorbs heat given off by the engine system. Heavy-duty coolant is more than just antifreeze. It is made up of glycol, water and chemicals that control liner pitting, corrosion, scale and more. Heat/energy is generated by the engine during the combustion process. The heavy-duty coolant absorbs the waste heat, preventing the engine from overheating, and must be maintained at the correct level and ratio recommended by the engine manufacturer in a particular operating environment.

In order for the heavy-duty coolant to function correctly, it must circulate freely throughout the system's passages and dissipate heat through the radiator. The water pump then circulates the coolant back to the engine where it absorbs more heat. Several of the water pump's components come into direct contact with the coolant.

Controlling the heat is the function of the thermostat. It must operate properly to ensure optimum engine temperature.

Potential Problems 40% of engine maintenance can be directly related to the cooling system. There are four potential problems: liner pitting, corrosion, scale, and water pump leakage.

Liner pitting or cavitation corrosion occurs when small holes form in the side of a cylinder liner. These holes allow coolant to be drawn into the combustion chamber at engine shutoff. Upon startup, hydraulic lock can occur, if coolant in the cylinder does not compress, and cause severe engine damage. Coolant in the oil can also damage engine bearings.

Liner pitting is caused when energy generated during the combustion process combines with the side to side motion of the piston and the liner vibrates at a very high frequency. This vibration causes small bubbles to form on the liner wall, which implode, and a high-speed jet of coolant hits the liner, eventually causing pitting. Unprotected engines with as little as 30,000 miles may experience pitting completely through the liner.

Corrosion can occur in any of the cooling system components. One cause of corrosion is poor water quality, especially when excessive levels of chlorides and sulfates are present. Corrosion can affect thermostat performance, water pump life and the radiator cap.

Scale build up on the cooling system components is a result of poor quality water. High calcium and magnesium levels in the water causes buildup on liners and inhibits heat dissipation. When scale builds up, the heat can't escape into the coolant, leading to liner distortion, which causes ring scuffing and, eventually, excessive ring wear and high oil consumption. Even a slight scale build-up can affect thermostat and radiator-cap efficiency and inhibit the coolant's flow through the radiator.

The Solution—Heavy-Duty Antifreeze and Coolant A good quality heavy-duty, fully formulated antifreeze provides freeze protection, boil over protection, and component protection.

A fully formulated antifreeze and coolant contains chemical additives that protect against corrosion and scale buildup. The Maintenance Council (TMC) and ASTM (American Society for Testing and Materials) provide standards for diesel engine antifreeze and coolants.