Chapter 8 - Caterpillar Engine and Related Systems
248
9c. Use the non-contact thermometer to moni-
tor the temperature in two spots as the
engine warms-up from a cold start:
Check the engine block adjacent to the
water pump.
Check the to-radiator pipe.
See Figure 8.72.
9d. Interpretation:
• If the two temperatures follow each-other
closely, the thermostat has been removed or has
failed in the open position.
• If the block temperature steadily rises past 160
deg.f. (71 deg.c.), and the temperature in the
pipe does not make a rapid shift upward, the
thermostat has failed in the closed position or
coolant is not circulating because of some other
problem (belt, water pump, obstruction).
• If the block temperature rises to nearly 160 deg.
f. (71deg.c.) and the to-radiator pipe remains
cool until that point then suddenly rises to the
same temperature, the thermostat is operating
correctly.
NOTE: The thermostat opens at 167 deg. f. (75
deg.c.), but the insulating properties of the metal
reduce the surface reading. There is a weep
hole in the body of the thermostat to allow some
movement of coolant, even when the thermostat
is closed. See Figure 8.73.
NOTE: The correct direction for thermostat
installation is with the copper-colored wax-stat
section facing into the water jacket of the engine.
If installed wrong-way-round it will not open at
the correct temperature. See Figure 8.74.
Figure 8.72
Figure 8.73
Weep hole
Figure 8.74
Thermostat
housing
NOTE:
correct
positioning
of the
thermostat
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