COOLING SYSTEM Figure 4.  - Radiator Top Tank Used With Continuous Deaeration Cooling System When the cooling system is filled through the upper portion of the tank, coolant enters the main cooling system at the water pump   and   fills   the   radiator   core   and   the   engine   from   the bottom, forcing air out the vents. The   basic   design   of   the   radiator   top   tank,   used   with   the continuous  deaeration  cooling  system,  can  be  seen  in  Figure 3.        The    tank    piping    can    be    seen    in    Figure    2.        These illustrations   are   not   for   a   particular   installation,   but   only   a typical installation. On some IH chassis, the radiator does not have a two section top  tank.    But,  the  chassis  still  has  a  continuous  deaeration cooling  system.    On  such  chassis,  the  upper  section  of  the radiator  top  tank  is  replaced  with  a  remote  mounted  surge tank, with external housing, that duplicates the function of the vent tube and the coolant make-up line. ENGINE WATER JACKET The  water  jacket  permits  coolant  to  be  circulated  around  the cylinder  walls,  combustion  chambers  and  valve  assemblies. Some  of  the  coolant  passages  are   small   and   can   become clogged   If   the   cooling   system   does   not   receive   the   proper maintenance. Close inspection should be given to the following areas: Core Plugs These are sometimes mistakenly termed "freeze plugs". The  plugs  are  present  due  to  engine  block  casting  methods and not to protect against expansion from freezing. Core   plugs   that   show   signs   of   leaking   or   rusting   through should  be  replaced.    Refer  to  respective  Engine  Manual  for core plug replacement. Drain Plugs The drain plugs located in the water.  jacket should receive seasonal care and be kept free of rust and scale. Gaskets Must be in good condition to prevent both internal and external leaks.    If  there  are  external  leaks  around  gaskets,  there  may also be internal leaks into the engine. Proper  tightening  of  the  head  bolts  with  a  torque  wrench  is essential for preventing leaks around the head gasket. WATER PUMP The   water   pump   circulates   the   coolant   through   the   cooling system.    It  should  be  checked  carefully  for  leaks  and  proper lubrication.  If leaking or in bad condition, it should be rebuilt or replaced    promptly.        For    water    pump    rebuild,        refer    to respective Engine Manual. FAN The fan should be checked for loose or bent blades.  A loose blade could work free during operation and cause damage.  A bent blade will reduce the fan’s efficiency. THERMOSTAT Thermostats  provide  a  means  of  retarding  or  restricting  the circulation  of  coolant  during  engine  warm-up.    An  inoperative thermostat  can  cause  engine  overheating  and  a  subsequent loss of coolant.  Thermostats can be tested by submerging in hot  water  and  noting  the  opening  and  closing  temperature. Use  an  accurate  high  temperature  thermometer   for   making this   test.      Refer   to   Engine   Manual   for   proper   opening   and closing temperatures. HOSES AND CLAMPS The   only   coolants   which   are   recommended   for   use   in   IH cooling  systems  are  those  which  contain  an  ethylene  glycol base.      Other   base   coolants   may   damage   rubber    hoses, especially those made of silicone rubber.  Type of rubber used can usually be determined by color.  Silicone hoses are made in    "COLOR"    while    other    rubber    hoses    are    "BLACK".        If coolants used are not of ethylene glycol base, this may affect your engine warranty. CAUTION - ANTI-FREEZE MADE WITH METHOXY PROPANOL OR PROPYLENE GLYCOL IS NOT RECOMMENDED   FOR   USE   WITH   IH   ENGINES.      THESE TYPES OF ANTI-FREEZE CAN DAMAGE ENGINE INTERNAL SEALS AND COOLANT HOSES AND CREATE A POTENTIAL    FIRE    HAZARD    DUE    TO    LOWER    FLASH POINTS THAN ETHYLENE GLYCOL TYPE ANTI-FREEZE. Hoses  and  clamps  should  be  checked  regularly  as  they  are often the source of hidden trouble.  Hoses may appear in good condition   on   the   outside   but   the   inside   may   be   partially deteriorated.  If there are any doubts about CTS-4181 Page 6