TM 10-3930-671-24 9. Use a coolant tester to test the low temperature protection ("freeze") level (proportion of ethylene glycol   to   water)   of   the   coolant   solution.      Add coolant    solution    (antifreeze    and/or    water)    to provide    maximum    cooling    system    protection (50/50 mixture). Cooling System Pressure Tests If   the   need   is   indicated   for   further   maintenance   and testing of the cooling system, check for both external and internal   leaks   in   the   cooling   system   with   an   accurate pressure pump and gauge tester. Cooling System Pressure (radiator cap): 14 psi (12- 16psi) Refer   to   Section   2.1,   Service   Specifications,   Cooling System. Radiator & Cooling System 1. Pressure test the radiator cap to determine if it is holding the correct pressure.  Wash cap in clean water    to    remove    dirt    or    scale    from    sealing surfaces.      Wet   rubber   sealing   surfaces   and install cap tightly on the tester.  Pressurize tester and radiator cap. 2. The gauge pressure reading should be within the specified limits of the cap relief pressure.  If the test  relief  pressure  either  exceeds  or  is  below the specified limits, replace cap. Radiator Cap 1. Pressure test the radiator and cooling system to determine   if   it   will   hold   the   correct   pressure without leaks or failure.   Wet  the  rubber  sealing surfaces  and  install  the  tester  cap  tightly  on  the radiator filler neck.  Apply pressure to the cooling system  equal  to  the  radiator  cap  specified  relief pressure. 2. Observe    gauge    reading    for    approximately    2 minutes.    Pressure  should  not  drop  during  this time.      If   pressure   drops,   check   for   leaks   in radiator, radiator cap, hoses, connections, engine components, etc. Thermostat 1. Remove    and    test    the    engine    thermostat    to determine if it closes correctly and  opens  at  the specified temperature. 2. Place   thermostat   fully   immersed   in   a   pan   of water.  Heat the pan slowly while stirring water to produce an even temperature. Use a thermometer   to    measure    the    temperature    at which   the   thermostat   valve   cracks   (starts   to open)  and,  when  it  is  fully  open,  measure  the valve  lift  distance  of  the  fully  opened  valve.    If test    results    are    not    to    specification,    replace thermostat. 3. Replace  the  thermostat  if  even  a  slight  opening of the valve at normal temperature is found or if its   appearance   shows   any   breakage.      If   the sensing  part  is  damaged,  the  thermostat  valve will remain closed. F-96