MOTOR TRUCK SERVICE MANUAL
COOLING SYSTEM
GENERAL
TROUBLE SHOOTING (Continued)
REMEDY
PROBLEM
POSSIBLE CAUSE
Engine Running
2. Linkage Adjusted to Tight.
2. Adjust linkage.
Too Cold (Continued)
3. Thermostat Dimensional
3. Remove shutter
Setting Incorrect.
control and adjust.
4. Incorrect Shutter Control
4. Install correct
Thermostat Temperature Range.
thermostat.
5. Faulty Shutter Control
5. Replace thermostat.
Thermostat.
6. Shutter Linkage Binding.
6. Free linkage.
NOTE
The degree rating of the engine thermostat and shutter control thermostat should be identical.
For example, if a 180 engine thermostat is used, a 180 shutter control thermostat unit should also be
used. The engine thermostat will open at approximately 180 and allow the coolant to flow to the radiator
top tank. As the coolant flows down through the radiator core, a drop in coolant temperature of
approximately 10 will take place. The shutter blades will remain closed until the coolant temperature in
the bottom tank is raised to the arbitrary figure of 180. This will cause the coolant temperature in the
engine to actually be slightly above 180 which will keep the engine thermostat open, allowing the shutter
control thermostat to control the operating temperature.
Shutter control thermostat units are available in temperature control ratings of 160, 170, 175 and 180.
Fig. 5 Shutter Control Thermostat Unit Adjustment.
250