7.6
Section 7
Cooling System
Figure 7-12. Intake/Thermostat.
To Test
Remove the thermostat from the system. Hang or
suspend the thermostat by its frame in a container of
water, so the thermostat does not touch the bottom of
the container. Heat the water and measure the
temperature (an oven thermometer can be used). The
spring-loaded valve of the thermostat should begin to
open at 79.4°C (175°F), and can be completely open
at 90°C (195°F). If the valve opens at a temperature
more than 10 degrees below the specified opening or
fails to open at a temperature 10 to 15 degrees above
the specified opening, the thermostat should be
replaced. If the valve in the thermostat can be moved
or pushed off its seat with a slight effort when the
thermostat is cold, the unit may be considered
defective and should be replaced. The thermostat
should be replaced if operation is found to be
questionable or faulty.
Installation
1. Thoroughly clean the sealing surfaces of the
intake manifold and thermostat housing with an
aerosol gasket remover. Make sure the sealing
surfaces are clean and free of nicks or damage.
Make sure the notch in the intake manifold is
clean.
2. Install a new thermostat into the intake manifold,
so the larger spring end is down into the well of
the intake manifold. Position a new thermostat
gasket on the intake manifold.
3. Install the thermostat housing onto the intake
manifold.
4. Install and torque the two hex. flange screws to
9.9 N·m (88 in. lb.).
Figure 7-13. Warning Devices.
If the warning device activates, or the engine kills,
indicating an excessive operating temperature, check
the following:
1. Make sure fan belt is in good condition and
properly tensioned.
2. Make sure cooling fan is properly secured, not
broken, damaged, or missing blades.
3. Make sure all air intake and cooling surfaces are
clean and free of debris accumulation.
Temperature Sensor
Audible Alarm
5. Reconnect the radiator hose and secure with the
hose clamp, if separated previously.
High Temperature Sensor
A high temperature sensor may be mounted in the
intake manifold and is used to activate a warning light,
audible alarm, or kill the engine (depending on the
application), if the safe operating temperature is
exceeded. The sensor is a ‘‘normally open’’ switch
which completes a circuit, when the coolant
temperature reaches the rated temperature limit of the
switch. For these engines the temperature sensor limit
is 123.8°C (255°F).
Intake
Manifold
Thermostat
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