TM 10-3930-671-24 There  are  instances  where  this  corrosive  element  has eaten holes through cast iron parts such as water pump impellers   and   bodies.      This   condition   is   caused   by electrolysis  taking  place  in  the  parts  involved.    Where these conditions exist, water filters should be incorporated in the assembly to remove these troublesome elements and off-set the electrolytic action. EFFECT OF ALTITUDE ON COOLING Water    boils    at    212°F    (100°C)    under    atmospheric pressure  at  sea  level.    This  pressure  becomes  less  at higher altitudes and the reduced pressure causes water and other liquids to boil at a lower temperature. ANTI-FREEZES Water   freezes   at   32°F   (0°C),   forming   solid   ice   and expanding about 9% in volume-which causes tremendous pressure and serious damage when allowed to  freeze  inside  the  cooling  system.    When  operating temperatures are below 32°F (0°C), an anti-freeze liquid must  be  added  which  will  lower  the  freezing  point  to  a safe margin below the anticipated temperature of outside air.    Permanent  anti-freeze  will  also  raise  the  boiling temperature  of  the  coolant.    The  correct  proportion  of anti-freeze  is  also  important  when  the  engine  is  to  be operated under high ambient temperature conditions. CORROSION INHIBITORS Corrosion  inhibitors  can   cause   damage to  the  eyes  or  skin.    n  contact  is  made, immediately  wash  skin  with  water.    For the eyes, Immediately flush the eyes with water    for    several    minutes.        In    either event, seek prompt medical attention. Water forms rust due to its natural tendency to combine chemically with iron and air in the system.  Rust inhibitors for   water   are   inexpensive,   simple   to   use   and   make cleaning  and  flushing  necessary  only  after  long  periods of operation. The addition of a corrosion inhibitor is not necessary if an anti-freeze containing a rust inhibitor is used. RADIATOR The  radiator  or  heat  exchanger  consists  of  a  series  of metal  tubes  through  which  the  coolant  is  circulated.    In standard radiator design fins are connected to the metal tubes  to  give  an  extended  surface  through  which  heat can  be  dissipated.    It  is  important  that  these  tubes  be kept clean on the inside and the  fins  free  of  dirt  on  the outside so the maximum heat transfer can take place in the radiator. Blowing   out   between   the   fins   of   the   radiator,   using compressed air, in a direction opposite to that of the fan circulated air, will serve to keep  the  cooling  surfaces  of the   core   free   of   dirt   and   other   particles.      Operating conditions  will  determine  the  frequency  of  this  service. Every  500  hours  of  operation  the  radiator  and  cooling system  should  be  well  cleaned  and  flushed  with  clean water. Radiator Coolant Inlet Wherever possible, only soft clean water should be used in  the  cooling  system.    Hard  water  will  cause  scale  to form  in  the  radiator  and  the  engine  water  jackets  and cause poor heat transfer.  Where the use of hard water cannot  be  avoided  an  approved  water  softener  can  be used. CLEANING COOLING SYSTEM Deposits   of   sludge,   scale   and   rust   on   the   cooling surfaces  prevent  normal  heat  transfer  from  the  metal surfaces to the coolant and, in time, render the cooling F-146