Geely EC715 2009, Workshop Manual

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2.8.3 System Working Principle
2.8.3.1 System Working Principle
– Cold Engine: the engine normal operating temperature is
generally around 95°C (203 ºF), in this temperature range,
all the engine parts running status will be ideal. If the engine
can not reach the ideal operating temperature in a long
time,it will increase the parts wear and tear. Because of low
temperature, the mixture combustion will be inadequate,
and there will be excessive carbon residue. The engine
heat exchange must be kept minimum so the engine can
reach normal working temperatures in a short period of
time. At this point the thermostat controls the engine
coolant only circulates within the engine block, bringing the
heat from the cylinder wall to the other engine parts, so that
the temperature increases rapidly. Water pumps makes the
engine coolant flow in the cylinder block, then in the engine
block water jacket, throttle body and cylinder head cover.
This is called "small loop".
– Engine at normal working temperature: With the engine
running, the engine coolant temperature quickly increases,
when the thermostat reaches 82°C (179.6 ºF), the engine
coolant is drawn into the engine block water jacket, intake
manifolds, cylinder head and radiator by the water pump.
This is called "big loop".
–
Thermostat: the thermostat's role is to control engine
coolant flow in the cooling system. Thermostat is installed
in the front of the engine and sealed by the engine intake
pipe joints components, located in the front of the cylinder
head cover. Thermostat can prevent the engine coolant
flow from the engine to the radiator, warm up the engine
quickly and adjust the engine coolant temperature. When
the engine coolant temperature is low, the thermostat in the
closed position, preventing the engine coolant circulating
through the radiator. At this point, it only allows the engine
coolant circulates through the heater core, and thus quickly
and evenly warm up the engine. When the engine is warm,
the thermostat opens. The engine coolant flows through
radiator and exchanges the heat. Thermostat opening and
closing, allow sufficient engine coolant enter into the
radiator, maintain the engine at normal operating
temperature range. The wax ball inside the thermostat is
sealed in a metal casing. Thermostat wax ball thermal
expands when warm and contracts when cold. As the
vehicle drives and the engine warms up, engine coolant
temperature increases. When the engine coolant reaches
the required temperature, the thermostat wax ball expands,
puts pressure on the metal shell and opens the valve. This
allows the engine cooling fluid flow through the engine
cooling system and engine cools down, when the wax ball
contracts, under the action of the spring, the valve will
close. Thermostat opening temperature is 82°C (179.6 ºF),
and fully open temperature is 95°C (203 ºF).
– Cooling Fan Low-Speed Circuit Description: Engine cooling
fan circuit controls the main cooling fan and auxiliary
cooling fan. Cooling fan is controlled by the engine control
module (ECM) according to the engine coolant temperature
sensor and air pressure switch inputs. ECM monitors
conditions that meet the cooling fan Low-Speed running
conditions, ECM controls the engine wiring harness
connector EN01 terminal No.62 internal ground, and the
Low-Speed cooling fan relay pull-in. Power passes through
the low speed relay terminal No.87 to reach the cooling fan
wiring harness connector CA16 terminal No.1 and then
through the speed limit resistor, and finally reaches to the
paralleled two fan motors. Fan motors negative is
connected to the ground through the cooling fan wiring
harness connector CA16 terminal No.3. Therefore, the
Low-Speed fan motor starts running.
2-458 Cooling System JL4G18-D Engine
EC718/EC718RV EC715/EC715RV 10/2009