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Fan and Shroud - 14081_47
Figure  1-50.-Expansion  tank.

Equipment Operator Basic - Beginning construction equipment operators manual
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Figure  1-48.-Thermostat  operation. from the block to the pump when the passage to the radiator is blocked by the closed thermostat (fig. 1-48). Some  stationary  engines  and  large  trucks  are equipped with shutters that supplement the action of the thermostat  in  providing  a  faster  warmup  and  in maintaining proper operating temperatures. When the engine  coolant  is  below  a  predetermined  temperature, between 185°F to 195°F, the shutters, located in front of the radiator, remain closed and restrict the flow of air through the radiator. Then, as the coolant reaches proper temperature,  the  shutters  start  to  open. AIR-COOLING SYSTEM The simplest type of cooling is the air-cooled, or direct method, in which the heat is drawn off by moving air in direct contact with the engine. The rate of the cooling is dependent upon the area exposed to the cooling air, the heat conductivity of the metal used, the volume of the metal or its size in cross section, the amount of air flowing over the heated surfaces, and the difference  in  temperature  between  the  exposed  metal Overflow Tank The overflow tank serves as a receptacle for coolant forced out of the radiator overflow pipe and provides for its  return  to  the  system.  As  the  engine  cools,  the balancing of pressures causes the coolant to siphon back into the radiator. Cooling systems using an overflow tank are known as closed cooling systems (fig. 1-49). Coolant is usually added to this system through the overflow tank that is marked  for  proper  coolant  level.  NEVER remove  the radiator cap located on the radiator unless you are positive the system is cold. If there is any pressure in the radiator, it will spray you with hot steam and coolant. Use  extreme  caution  when  performing  operator’s maintenance on a closed cooling system. Expansion Tank Some engines use an expansion tank in their cooling system (fig. 1-50). The tank is mounted in series with the upper radiator hose and is used to supply extra room for coolant expansion and generally takes the place of the upper radiator tank. The pressure cap and the overflow  line  are  also  mounted  on  the  expansion  tank. Figure 1-49.-Closed cooling system. 1-36







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