CHAPTER 5
INTERNAL COMBUSTION ENGINE COOLING AND
LUBRICATING SYSTEMS
The necessity for cooling may be emphasized by
INTRODUCTION
considering the total heat developed by an ordinary
six-cylinder engine. It is estimated that such an engine
All internal combustion engines are equipped with
operating at ordinary speeds generates sufficient heat
cooling and lubricating systems that work in
to warm a six-room house in freezing weather. Also,
conjunction with each other to promote efficient
peak combustion temperatures in gasoline engines
engine operation and performance. The cooling and
may reach as high as 4,500F, while that of a diesel
lubricating systems discussed in this chapter, along
engine may approach 5,000F. Some of this heat is
with their respective components and maintenance
absorbed by the valves, pistons, cylinder walls, and
requirements, are representative of the types of
cylinder head, all of which must be provided with some
systems you will be expected to maintain.
means of cooling to avoid excessive temperatures.
Because of the variety of engines used in support
Thus, even though very high temperatures may be
equipment, there are differences in the applications of
reached by the heated gases, the cylinder wall
features of their cooling and lubricating systems. Keep
temperatures must not be allowed to rise beyond 400
in mind that maintenance procedures and operational
to 500F. Temperatures above this will result in serious
characteristics vary from engine to engine; therefore,
damage, as already indicated. However, for best
always refer to the manufacturer's instructions for
thermal efficiency, it is desirable to operate the engine
specific information.
at temperatures closely approximating the limits
imposed by the lubricating oil properties.
COOLING SYSTEMS
The purpose of the cooling system is to absorb and
remove or transfer heat from the engine as well as
LEARNING OBJECTIVES: Identify the
regulate the operating temperature of the engine for
components of gasoline and diesel engine
best efficiency. About 25 percent of the heat produced
cooling systems. Identify procedures for
in the combustion chambers by the burning of fuel is
inspecting, repairing, and removing and
dissipated via the cooling system, along with the
replacing gasoline and diesel engine cooling
lubrication and fuel systems. Nearly 50 percent of the
systems.
Identify procedures for
heat produced passes out with the exhaust gases. An
troubleshooting gasoline and diesel engine
additional function of the cooling system is that of
cooling systems.
controlling the temperature in the vehicle passenger
compartment to a comfortable range in cold weather,
usually through use of hot water heaters.
The internal combustion engine produces power
Air is the only thing that is continually present in
by burning fuel within the cylinders, and is sometimes
large enough quantities to cool the running engine.
referred to as a "heat engine." However, only about 25
Vehicles are designed to dissipate the heat from the
percent of the heat is converted into useful power for
engine into the air through which they pass. This is
propelling the vehicle or for doing other work. What
accomplished either by direct air-cooling or indirectly
happens to the remaining 75 percent of the heat? It is
by liquid cooling. Thus, in the final analysis, the
largely absorbed by the engine parts or passes out with
c o o l i n g o f a l l a u t o m o t ive e n g i n e s i s a c t u a l l y
the exhaust gases. If this heat were not removed
air-cooling, regardless of whether they are classified as
quickly, overheating and extensive damage to the
air-cooled or liquid-cooled. In this chapter we will
engine would result. Valves would burn and warp,
discuss both types to include a description of the
various components of the systems and an explanation
would overheat and seize, and the engine would soon
of their operation.
stop.
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