TM 1-1500-204-23-1 5 If  not  more  than  two  additional granular  particles  are  found  during  screen  and  sump inspection   after   runup,   engine   may   be   released   for service  in  accordance  with  the  applicable  maintenance manual. (b) When  aluminum  flakes  are  found, proceed as follows: NOTE Aluminum flakes may not necessarily require    engine    removal    In    winter operations, when warped piston ring lands     are     frequent,     considerable quantities  of  aluminum  from  pistons may   be   discharged   Into   engine   oil system.        It    will    be    necessary    to exercise judgment before continuing with    the    following    procedure,    for Instance,   if   oil   sump   or   screen   is found     choked     with     a     mass     of aluminum flakes or particles, regardless of size, it will probably be necessary   to   remove   engine   even though faulty piston can be located. 1 Make   a   careful   Inspection   of cylinders    by    examination    of    cylinder    bores    and    a compression check In an effort to locate faulty piston. 2 When  not  more  than  two  faulty pistons   are   found,   change   faulty   piston   and   cylinder assemblies   before   continuing   with   procedure.      When more than two faulty pistons are found, remove engine If  two  or  less  faulty  pistons  are  found,  continue  with procedure. 3 Drain  oil  system,  flush  oil  tank, and clean oil screen. 4 Test  engine  In  accordance  with the applicable maintenance manual. 5 If    more    than    five    additional aluminum   flakes   are   found   during   screen   and   sump inspection after runup, remove engine.  If less than this quantity is found, engine may be released for service in accordance with the applicable maintenance manual. (4)   Silver particles.  Silver particles in granular form  indicate  a  master  rod  bearing  failure  in  advanced stages.  When these particles are found in any quantity, remove   engine.      Silver   is   used   in   plating   numerous other   parts,   and   silver   flakes,   not   exceeding   10   in number, do not necessarily indicate a part failure.  Since silver  is  quite  soft,  some  small  flakes  will  occasionally be  released  by  normal  working  of  these  parts.    A  very small  quantity  of  silver  from  master  rod  bearings  will make a large number of tiny flakes as it passes through roller bearings or gears within engine.  Large quantities of silver flakes indicate an excessive loss of bearing or plating   surface   and   engine   must   be   removed   as   a precautionary measure. (5) Copper  or  bronze  particles.    Copper   or bronze   particles,   in   granular   form   and   in   quantities greater than a few particles, indicate disintegration of a bushing  or  valve  guide  and  engine  must  be  removed. Copper or bronze flakes, in quantities not exceeding 10 flakes,  do  not  necessarily  indicate  part  failure.    Bronze flakes may be formed in small quantities through normal seating  of  bushings  or  valve  guides.    Larger  quantities of   copper   or   bronze   flakes,   however,   may   Indicate excessive  loss  of  bushing  metal  and  engine  must  be removed as a precautionary measure. g. Additional   Metal   Particles   Test.      This   test   is made to subject engine to sufficient operations to cause any additional metal in oil system to collect on oil screen and   in   main   sump   and   also   to   reveal   any   Incipient trouble.    This  additional  metal  will  determine  whether engine  needs  to  be  removed  or  allowed  to  continue  In service Test using the following procedures. (1) Drain and flush external oil system (2) Run    engine    to    bring    it    to    operating temperatures   and   make   a   minimum   of   three   power checks  (Allow  engine  to  cool  between  checks).    Take care not to exceed allowable limits for ground operation. (3) Again   remove   oil   screens   and   examine for metal accumulation.  Examine main sump plug and screen for metal accumulation.  If engine is released for service, it must be watched closely for next 25 hours for any indications of malfunctions or internal failure. h. Excessive Spark Plug Copper or Silver Runout. If  copper  runout  is  noted,  replace  cylinder  from  which spark  plug  was  removed  as  this  Indicates  the  cylinder temperature   has   exceeded   1981 °F   (1083 °C).      Silver runout   may   be   caused   on   a   fine   wire   electrode-type spark   plug   if   plug   is   subjected   to   pre-ignition   and/or detonation.      Excessive   temperature   may   cause   the silver spindle of the center electrode to flow toward the firing   end   of   the   electrode.      Copper   or   silver   runout indicates affected cylinders should be replaced. Engines  having  runout  on  more  than  25  percent  of  the cylinders should be removed. 7-27