d. Air Shutter System. The radiator shutters are operated by an air cylinder connected with a shutterstat and an air
filter to an air line from the air receiver. The shutterstat is mounted in the coolant connection between the water pump
body and the radiator. As long as the temperature of the coolant remains normal (below 180 F.), the air line from the air
receiver to the air cylinder is "open" and the cylinder plunger holds the pivoting shutter lever in a raised position to keep the
radiator shutter closed. However, as the temperature of the coolant approaches 180 F., the shutterstat element expands,
forcing the needle valve toward its Seat. Thus, the air pressure to the cylinder is decreased gradually, and the cylinder
spring forces the plunger toward the cylinder air inlet. The shutter lever is pivoted downward, opening the radiator
shutters.
80. Flushing the Cooling System
The entire cooling system must be flushed approximately every 1,024 hours of operation to remove dirt, foreign
matter, and liming deposits. In hard water areas, flush the system more frequently. The flushing procedure is as follows:
a. Open the radiator drain cock and the two drain cocks in the crankcase, and drain all coolant from the entire
system.
Note. One crankcase drain cock is located on each side of the engine-compressor crankcase. Be
sure to open both drain cocks.
b. Prepare a cleaning solution of one pound of washing soda to every three gallons of water (a total of 5 1/2 pounds
of washing soda and 16 1/2 gallons of water). Close the radiator drain cock and fill the system with the cleaning solution.
c. Start the engine and allow it to run for 30 minutes after it has reached normal operating temperature (180 to 215
F.).
d. Drain the cleaning solution from the cooling system (a, above) and thoroughly flush the system with clean, soft
water to remove all traces of solution.
e. After the system has been thoroughly flushed with clean soft water, close the radiator drain cock and fill the
cooling system with 10-gallons of antifreeze solution and 6 1/2 gallons water. Add an acceptable rust inhibitor.
81. Shutterstat
a. Removal.
(1) Close the shutoff cock (29) in the air filter air inlet line (27).
(2) Disconnect the air line (9) from filter to shutterstat and the elbow (10) at the top of the shutterstat.
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