TM 10-3930-671-24 The   function   of   the   cooling   system   is   to   prevent   the temperatures in the combustion chamber from damaging the  engine  and  at   the   same   time   keep   the   operating temperatures within safe limits. Maintaining the cooling system efficiency is important, as engine    temperatures    must    be    brought    up    to    and maintained within satisfactory range for efficient operation;   however,   this   system   must   be   kept   from overheating    in    order    to    prevent    damage    to    valves, pistons, and bearings. Never  pour  cold  water  or  cold  anti- freeze   into   the   radiator   of   an   over- heated  engine.    Allow  the  engine  to cool and avoid the danger of cracking the   cylinder   head   or   block.      Keep engine running while adding coolant. COOLING SYSTEM All Continental industrial diesel engines have the coolant force-circulated  by  a  water  pump  and  use  a  thermostat and by-pass system to control the temperature range. The coolant from the pump enters the front of the block, passing  along  and  between  the  cylinder  bores  and  is metered by the head gasket into and across the cylinder head to cool the pre-combustion chambers, valve seats, and guides. Upon  leaving  the  cylinder  head,  the  coolant  enters  the thermostat   housing,   in   which   is   mounted   the   positive shut-off   thermostat   that   controls   the   opening   to   the radiator or heat exchanger.  Upon being discharged from the thermostat housing, the coolant enters the radiator or heat  exchanger,  depending  upon  the  application,  where it  is  cooled  before  reentry  into  the  engine.    Continental industrial   diesel   engines   operate   most   efficiently   with coolant temperatures of 1800 - 200°F (810 93°C) and a thermostat  and  bypass  system  is  used  to  control  these temperatures. The thermostat valve remains closed and only allows the coolant  to  circulate  within  the  engine  itself  until  normal operating  temperatures  are  reached.    This  provides  for both  rapid  and  even  temperature  increase  of  all  engine parts    during    the    warm-up    period.        When    desired temperature   is   reached,   the   thermostat   valve   opens allowing  all  the  coolant  to   circulate   through   both   the engine and radiator while shutting-off the bypass system. IMPORTANT Present thermostats begin to open at 81°C  (180"F)  and   are   fully   open   at 940C (202°F).  Operation of engines in this temperature range is not harmful. However, temperature gauges are not always  accurate  and  may  sometimes Indicate higher than actual temperature.  This can lead operators to   believe   engines   are   overheating when    they    are    actually    operating normally. Sectional View showing Coolant Passages in Head & Block EXPANSION OF WATER Water    has    always    been    the    most    commonly    used coolant  for  internal  combustion  engines  because  it  has excellent   heat   transfer   ability   and   is   readily   obtained everywhere.  Like all liquids, it expands when heated (the rate of expansion being 1/4 pint per gallon (1/32 liter per liter)  when  the  temperature  is  raised  from  40°  to  180°F (40 to 81°C). For   example:      If   a   4   gallon   cooling   system   is   filled completely full of water at 40°F (4°C), 1 pint will be lost through the radiator overflow pipe by the time the water temperature reaches 180°F (81°C). WATER FILTERS In some areas, the chemical content of the water is such that  even  the  best  of  rust  inhibitors  will  not  protect  the cooling system from the formation of rust and scale. F-145 Section 4- Cooling System