COOLING SYSTEM (160-180F).        Stop    engine,    remove    radiator    cap carefully    (if    so    equipped)    and    drain    system    by opening drain cocks on radiator and crankcase. 2. Allow   engine   to   cool,   close   drain   cocks   and   pour cleaning compound into radiator, according to directions.  Fill system with water. 3. Place a clean drain pan to catch overflow and use to maintain  level  in  radiator.    Avoid  spilling  solution  on vehicle paint. 4. Install radiator cap (if so equipped) and run engine at moderate  speed,  covering  radiator  if  necessary,  so the radiator reaches a temperature of 84°C (180F) or above but does not reach the boiling point.  Allow the engine  to  run  at  least  two  hours  at  84C  (180F)  so the  cleaning  solution  will  take  effect.    Do  not  drive vehicle  or  allow  liquid  level  in  radiator  to  drop  low enough to interfere with circulation. NOTE   -   Stop   engine   as   often   as   necessary   to prevent boiling. 5. With  the  engine  stopped,  feel  the  radiator  with  bare hands to check for cold spots, and then observe the temperature  reading.    Where  there  is  no  change  in temperature    for    some    time,    drain    the    cleaning solution. 6. If   clogging   of   the   core   is   relieved   but   not   fully corrected, allow the engine to cool, pressure-flush the system (see Pressure Flushing), and repeat cleaning operation. 7. If  clogging  of  core,  indicated  by  cool  spots  on  the core  is  not  relieved,  radiator  core  must  be  removed for    mechanical    cleaning.        Mechanical    cleaning requires   removal   of   upper   and   lower   tanks   and rodding out the accumulated rust and scale from the water passage of the core. PRESSURE FLUSHING 1. Disconnect  the  upper  radiator  hose  which  connects the   radiator   core   to   the   engine   water   outlet   and remove thermostat from engine water outlet. 2. Clamp  a  convenient  length  of  hose  to  the  radiator core   outlet   opening   and   attach   another   suitable length  of  hose  to  the  radiator  inlet  opening  to  carry away the flushing stream. 3. Connect   the   flushing   gun   to   compressed   air   and water pressure and clamp the gun nozzle to the hose attached to the radiator outlet opening. 4. With  radiator  cap  (if  so  equipped)  on  tight,  fill  core with   water.      Apply   air   pressure   in   short   blasts   to prevent core damage. 5. Continue  filling  radiator  with  water  and  applying  air pressure  in  short  blasts  until  the  water  comes  out clear. 6. Clamp   the   flushing   gun   nozzle   firmly   to   a   hose attached securely to the engine water outlet opening. Fill engine block with water, partly covering water inlet opening to permit complete filling. 7. Apply  compressed  air  to  blow  out  water  and  loose sediment.  Continue filling with water and blowing out with air until flushing stream comes out clear. 8. For  badly  clogged  engine  water  jackets  that  do  not respond to regular pressure flushing, remove engine cylinder head and core hole plugs and with a suitable length of small copper tubing attached to the flushing gun   nozzle,   flush   the   water   jackets   through   the openings. 9. If the vehicle is equipped with a heater connected to the  cooling  system,  flush  the  heater,  following  the same procedure as for the radiator core. 10. After completing the flushing operation, clean out the- radiator overflow pipe, inspect the water pump,  clean the  thermostat  and  the  radiator  cap  control  valve  (if so equipped).  Check thermostat for proper operation before installation.  See "Thermostat." 11. Blow insects and dirt from radiator core air passages, using water if necessary. FILLING THE COOLING SYSTEM To eliminate air being trapped within the engine or heater, the following procedure should be followed when filling the engine coolant system. 1. Set parking brake. 2. Fill  cooling  system  until  coolant  reaches  bottom  of radiator   filler   opening.      Let   stand   approximately   5 minutes; recheck level. 3. Start engine. 4. Allow engine to operate, without radiator cap, at a fast idle   until   the   engine   reaches   its   normal   operating temperature. 5. After engine reaches its normal operating temperature, trapped air will be expelled from system. 6. With engine still running, add sufficient coolant to fill system.  If the radiator has a filler neck extension with a vent hole near the top, the system is full when the coolant level is at the bottom of the extension.  If the radiator does not have an extended filler neck,  fill the system  to  approximately  25.4mm  (1  inch)  below  the bottom of the filler neck. TEST EQUIPMENT To aid the serviceman in maintaining the cooling system at top efficiency,   various   items   of   test   equipment   are   available. Among these are the Cooling System Pressure Tester and the Hydrometer. CTS-4181 Page 9