COOLING SYSTEM CAUTION - CORRECT THIS CONDITION IMMEDIATELY OR SERIOUS DAMAGE TO ENGINE WILL RESULT. Boiling May be caused by any of the following: 1. Radiator or other parts of cooling system clogged with rust or scale. 2. Grille or bug screen clogged. 3. Radiator core fins damaged. 4. Thermostat defective -  stuck closed. 5. Water pump leaking air into system. 6. Radiator hose collapsed or rotting inwardly. 7. Radiator pressure cap defective. 8. Cylinder  head  loose,  causing   exhaust   gas   leakage into cooling system. 9. Water pump impeller corroded or loose on shaft. 10. Anti-freeze    protection    inadequate,    causing    partial freeze-up. After-Boil Boiling which may occur in a cooling system after the engine is shut off even though it did not occur during operation is known as after-boil.  This condition, which usually happens to cooling systems  that  need  attention,    occurs  because  the  coolant  is still picking up heat from the engine and the heat is not being dispersed by circulation through the radiator.  Other causes of after-boil    are    over-protection    or    use    of    high-temperature thermostat  with  alcohol-type  anti-freeze,  improper  installation of the thermostat, or a thermostat that is operating improperly. Foaming Foaming of coolant may also cause coolant loss.  This occurs only   with   a   very   dirty   cooling   system    and    under    severe operating  conditions.    Usually  an  air  or  exhaust  leak  in  the system  contributes  to  foaming  and  this  is  caused  by  a  faulty gasket,  leaky  radiator  hose  or  water  pump  seal.    Foam  is  an excellent   insulator   and   can   seriously   interfere   with   proper circulation. Evaporation Evaporation   reduces   the   amount   of   coolant   in   the   system. This is a common occurance where alcohol-base types of anti- freeze are used.  A faulty pressure cap may also be the cause of evaporation. CAUSES OF OVERHEATING Cooling System 1. Low coolant supply. 2. Leaks     at     any     of     the     following:     gaskets,     hose connections,    water    pump,    radiator,    heater,    core plugs, drain cock or plugs, cracked head or block. 3. Broken or loose fan belt. 4. Radiator clogged. 5. Collapsed or clogged hose. 6. Defective pressure cap. 7. Worn or corroded impeller on water pump. 8. Foaming. 9. Radiator air flow obstructed. 10. Bent fan blade. 11. Improper or defective thermostat. Miscellaneous 1. Clogged muffler or tail pipe. 2. Stiff re-built engine. 3. Dragging brakes. 4. Low engine oil level. 5. Engine overloaded. CAUSES OF OVERCOOLING 1. Missing thermostat. 2. Defective thermostat stuck open. 3. Short runs and intermittent driving. TROUBLESHOOTING THE CONTINUOUS DEAERATION COOLING SYSTEM If the  engine  fails  to  reach  normal  operating  temperature,  the following checks should be made to find the possible cause: 1. Visually  inspect  the  thermostat  to  be  sure  it  is  the correct thermostat and has the proper range. 2. Check  the  thermostat  to  make  sure  the  valve  is  not held  open  by  foreign  matter  and  that  the  thermostat valve closes with a good seal. 3. Check  the  operation  of  the  thermostat  in  a  pan  of water.  Heat the water.  The thermostat should begin to   open   at   about   95°C   (170°F).      The   thermostat should   be   fully   open   at   102C   (185F).      At   any temperature   below   95°C   (170F),   the   thermostat valve should be tightly closed. 4. The  engine  will  not  warm  up  properly  if  accessories such  as  heaters,  air  compressors  or  cooling  system water filters are not connected in the proper manner. These  accessories  should  not  be  connected  so  that the  outlet  coolant  goes  to  the  radiator  core.    These units  should  not  be  connected  to  the  make-up  line, because the make-up line will not be large enough to carry the excess coolant. CTS-4181 Page 11