TM 1-1500-204-23-1 NOTE Excessive damage requires replacement. (2) Tighten  loose  mountings  to  obtain  torque values specified In maintenance manual. (3) Repair  or  replace  vibration  isolators  that show any evidence of radial slippage. (4) Properly secure all engine mount retaining bolts with safety wire. (5) Replace vibration isolators when metal or rubber parts indicate sagging or deterioration. 7-12.        Preservation    of    Reciprocating    Engines. Corrosion of aircraft metals and alloys is primarily a light against moisture.  There are two main types of surface corrosion,     direct     chemical     attack     on     metal,     and electrochemical     action     In     which     the     metal     being corroded  becomes  a  part  of  an  electrolytic  cell  In  the presence  of  moisture.    Both  reactions  are  effectively retarded In the absence of moisture.  Corrosion will not occur   in   a   clean   atmosphere   when   moisture   is   not permitted    to    reach    the    metal    surface.    Preserve reciprocating engines using the following paragraphs. a. Preservation of Accident-Involved Engines. Engines    removed    from    an    aircraft    that    has    been involved   in   an   accident   In   which   engine   failure   or malfunction Is known or suspected to have been a factor should   not   be   treated   with   corrosion   protective.      No attempt     should     be     made     to     operate,     motor,     or disassemble  an  accident-involved  engine.    All  accident involved   engine   must   be   transported   to   an   overhaul depot or a designated investigation area within 10 days after  the  accident.    The  accident-involved  engine  shall be preserved using the following procedures. (1) Without    disconnecting    lines    or    fittings, make  every  effort  to  prevent  remaining  fuel  and  oil  In engines from leaking out (2) Plug all ports and cap all fittings and lines. Seal openings with applicable covers. (3) Install   engine   in   bottom   half   of   metal, reusable shipping and storage container. (4) Ground  engine  to  container  to  prevent  a possible  explosion  of  dangerous  vapors  which  may  be ignited by static electricity or a spark. (5) Secure all loose metal components to the container  with  tape,  PPP-T-60,  to  prevent  a  possible spark during shipment. b. Preservation     of     Operable     Engines     to     be removed  for  Overhaul.    Engines  to  be  removed  from aircraft   for   overhaul,   that   can   be   operated   without further damaging the engine or any of its parts, shall be preserved using the following procedures CAUTION While injecting the preservation compound,    be    sure    none    of    the compound  is  injected  into  airstream of  the  carburetor  or  master  control. Do not inject the compound upstream of the throttle valve. Damage may otherwise result. (1) Drain  oil  system  and  refill  with  corrosion preventive MIL-C-6529, Type II. NOTE Type II corrosion preventive consists of   a   ready   mixed   blend   of   1   part corrosion preventive, MIL-C-6529, Type  1  and  3  parts  new  lubricating oil, MIL-L-6082, Grade 1100. (2) Prior    to    starting    engine    for    final    run, connect discharge nozzle. NOTE Discharge  nozzles  shall  conform  to designs  set  forth  in  figure  7-24  and be   modified   in   length   and   thread configuration to suit engine type and point of application. (3) Locate    nozzle    in    a    position    so    that corrosion preventive mixture Is properly distributed to all cylinders.      Modify   nozzle   discharge   are   to   provide sufficient   restriction   to   prevent   exhausting   corrosion preventive supply prior to cessation of engine rotation. NOTE For radial engines, precautions shall be  taken  to  ensure  that  the  quantity of  mixture  aspired  and  the  location employed  provides  an  even  amount of  coating  for  both  upper  and  lower cylinders. 7-40