COOLING SYSTEM and   attacks   and   coats   the   metallic   surfaces   of   the   cooling system.      This   coating   reduces   the   heat   transfer.      Cooling system  conditioners  which  contain  these  inhibitors  must   be added  to  maintain  corrosion  protection.    These  conditioners are available as a liquid or in a coolant filter. Freezing Point C (F) Percentage Anti- Freeze Concentrat ion by Volume Specific Gravity @ 16°C (60°F) 0^° (+ 32) 0 1.000 - 7^° (+20) 15 1.025 -12° (+10) 25 1.040 -18° (0) 33 1.053 - 23^° (-10) 40 1.062 29% (- 20) 45 1.070 -34° (-30) 48 1.074 -40° (-40) 53 1.080 -46° (-50) 56 1.088 -51° (-60) 59 1.092 -57° (-70) 62 1.095 -63° (-80) 65 1.097 -68° (-90) 67 1.098 - 69^° (- 92) 68 NOTE: As shown below, a further increase in antifreeze volume increases the freezing point. -63° (-80) 71 1.100 -57' (-70) 75 1.106 -51° (-60) 79 1.110 -46° (-50) 83 1.113 -40° (-40) 87 1.117 -34° (-30) 91 1.119 - ^34° ( - 30) 95 1.123 -22° ^(- 8) 100 1.127 MT-28258 Figure 1.  - Coolant Mixture Freezing Points The   two   types   of   recommended   conditioners   are   as follows: 1. IH   coolant   conditioner   is   a   complete   inhibitor system, of a non-chromate type, which provides corrosion  protection,  pH  control  for  maintaining an   acid   free   coolant   and   water   softening   to prevent  the  formation  of  mineral  deposits.    It  is compatible  with  both  water  and  IH   anti-freeze and coolant. 2. The   coolant   filters   available   on    IH    vehicles, contain    a    blend    of    metaborate,    tetraborate, nitrite,  nitrate,    silicate,  M.B.T.,  phenolphthalein, and   an   organic   polymer   designed   to   provide superior     cooling     system     protection     to     that obtained  with  either  chromate  or  borate  coolant filters. These   coolant   filters   should    only    be    used    with ethylene  glycol  type  anti-freezes  that  do  not  contain anti-leak    additives.        The    anti-leak    or    stop    leak additives are removed by the water filter.  This could restrict coolant flow through the filter. 3. Soluble  oil  is  not  recommended  for  use  on  IH  truck engines  as  its  use  will  reduce  heat  transfer.    There are   no   miracle   additives   that   will   increase   heat transfer or prevent overheating.  Conditioned water is still the best coolant. COOLANT SYSTEM COMPONENTS The following is a list of the major components making up the cooling system.  Points  of  inspection  of  each  component  are covered in general terms. RADIATOR This component is one of the most important, as this is where most of the heat of the system is dissipated.  The radiator is made up of the following parts: Top and Bottom Tank Look  for  leaks,  particularly  where  tank  is  soldered  to  core. Vibration  and  pulsation  from  pressure  can  fatigue  soldered seams. Filler Neck The  sealing  seat  must  be  smooth  and  clean.    Cams  on  the filler neck must not be bent or worn, as this will not allow the cap  to  seal  properly.    Ensure  that  the  overflow  tube  is  not plugged. Tubes Because  these  are  very  small,  they  can  become  clogged,  or partially blocked, by rust and scale.  The general condition of the cooling system and operating temperature are indications as to the cleanliness of the tubes.  Another good test is to feel the core for cold spots. Fins These thin metal sheets radiate,  or  pass  off,  the  heat  picked up  by  the  tubes.    They  should  be  kept  free  of  bugs,  leaves, straw and other interference to allow free passage of air.  Bent fins should be straightened for maximum heat dissipation. Radiator Cap (Pressure-Sealing Type) Its   purpose   is   to   hold   the   cooling   system   under   a   slight pressure,  increasing  the  boiling  point  of  the  cooling  solution and  preventing  loss  of  the  solution  due  to  evaporation  and overflow. The  cap  (Figure  2)  has  a  spring-loaded  valve,  the  seat  of which   is   below   the   overflow   pipe   in   the   filler   neck.      This prevents the escape of air or liquid while the cap is in position. When  the  cooling  system  pressure  reaches  a  predetermined point,  the  cap  valve  opens  and  will  again  close  when  the pressure drops below the predetermined point. When   removing   the   pressure   type   cap   from   the   radiator, perform the operation in two steps.  Loosen the cap to its first notch   to   raise   the   valve   from   the   gasket   and   release   the pressure through the overflow pipe.  In the first stage CTS-4181 Page 4