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ENGINE COMPONENTS
36
9.0 THERMOSTAT:
Thermostat: Temperature Range 92
0
C
The thermostat controls the flow of coolant as
follows:
During a cold start, thermostat does not allow
coolant to flow to radiator since it is closed;
instead the coolant flows through thermostat
bypass outlet back to the engine. Thus short
circuiting of radiator which helps in attaining
engine working temperature in a very short period.
As soon as the coolant temperature reaches the
opening temperature (92
0
± 2
0
C) of the
thermostat, the thermostat valve starts opening
gradually and coolant starts flowing to the
radiator. At the same time the thermostat by-pass
starts closing gradually.
As the engine working temperature reaches
thermostat full open temperature (99
0
± 2
0
C), the
thermostat valve opens fully and thermostat by-
pass valve closes completely. In this condition
maximum quantity of engine coolant flows from
radiator to water pump.
A. Constructional Detail and Part List:
Constructional Details:
Part List:
Sr. No.
Part Description
1
Stem
2
Flange
3
Frame
4
Element
5
Main Spring
B. Testing Parameters:
Thermostat start open temperature is 92
0
± 2
0
C at 0.1 mm travel.
Full open temperature is 99
0
± 2
0
C at 7 mm
(Min.) travel.
Maximum thermostat travel 11.5 mm at 125
0
C.