D1146/D1146TI/DE08TIS
MAINTENANCE MANUAL
99
Printed in Jan. 2001 PS-MMA0415-E1A
4.1.3. Thermostat
z General descriptions and main data
The thermostat maintains a constant
temperature of coolant and improves
thermal efficiency of the engine by
preventing heat loss.
Namely, when the temperature of
coolant is low, the thermostat valve is
closed to make the coolant bypass to
directly enter the water pump; when the
coolant temperature rises to open wide
the thermostat valve, the bypass circuit
is closed and the water passage to the
radiator is opened so that the coolant is
forced to flow into the radiator.
Specifications
In moderate climates
Item
Bus Truck
In tropical climates
Type Wax-pallet type Wax-pallet type
Open at
79 °C 83 °C 71 °C
Open wide at
94 °C 95 °C 85 °C
Valve lift 8mm or more
10mm or
more
Bus : 8mm or more
Truck : 10 mm or more
CAUTION :
There are 2 kinds of thermostats
according to surrounding and operating
conditions. One is named by 71 °C type
and the other is 83 °C.
z Inspecting
(1) Check the wax pallet and spring for
damage.
(2) Put the thermostat in a container of
water, then heat the water slowly and
check temperature with a thermometer.
If the valve lift is 0.1 mm (starting to
open) at temperature of 83 °C and 8
Thermometer
Wood plate
Ruler
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