TM 10-3930-671-24 When  replacing  the  thermostat  in  the  water  header  be sure the counterbore is clean. When  installing  a  new  thermostat  in  the  water  header make sure that the temperature sensing unit goes in first or faces toward the cylinder head. Assemble    new    water    outlet    elbow    mounting    gasket Thermostat flange must seat in counter-bore with gas ket sealing contact between it and the outlet elbow. RADIATOR PRESSURE CAP If  the  coolant  Is  hot  or  if  the  engine has been running, loosen the pressure  cap  to  the  first  stop  and  let the    pressure    out    of    the    cooling system  before  removing  the  radiator cap. Many  operations  use  a  pressure  cap  on  the  radiator  to prevent overflow loss of coolant during normal operation. This  spring-loaded  valve  in  the  cap  closes  the  outlet  to the   overflow   pipe   of   the   radiator   and   thus   seals   the system,  so  that  pressure  developing  within  the  system raises  the  boiling  point  of  the  coolant  and  allows  higher temperatures  without  overflow  loss  from  boiling.    Most pressure valves open at 0.3 or 1.0 Bar (4 1/2 or 15 PSI), allowing steam and water to pass out the overflow pipe, however, the boiling point of the coolant at this pressure is 224°F (107'C) or 248OF (120'C) at sea level.  When a pressure   cap   is   used   an   air   tight   cooling   system   is necessary  with  particular  attention  to  tight  connections and a radiator designed to withstand the extra pressure. FAN BELT TENSION When tightening fan belts, loosen the alternator adjusting bolts and pull out on the alternator by hand until the belt is just snug.  Under no circumstances should a  pry  bar be  used  on  the  alternator  to  obtain  fan  belt  tension  or damage to the bearings will result. When  adjusted  correctly  the  fan  belt  deflection  on  the long side should not exceed 1/2" (13mm) . F-148