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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.
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