ARMY TM 9-2815-252-24 AIR FORCE TO 38G1-92-2 Section III.  GENERAL MAINTENANCE 3-3. GENERAL. This section provides general maintenance not found in other sections of Chapter 3. 3-3.1. General Instructions. Warning Where applicable, prior to performing engine maintenance, ensure batteries are disconnected. Failure to observe this warning could result in personal injury. NOTE Refer to end item maintenance manual for removal of any components necessary to gain access to engine. a. It  is  strongly  recommended  that  bolts  or  nuts  securing  cylinder  heads,  covers,  and  doors  be  tightened  in  proper sequence. b. When assembling an engine, it is always advisable to replace nuts, bolts and lockwashers that have been removed from  high  stress  locations,  in  particular  nuts  and/or  bolts  from  connecting  rods  and  cylinder  heads  should  be replaced. c. When assembling an engine it is always advisable to apply a small quantity of new lubricating oil to all moving parts. After any maintenance work on engine has been completed lubricating oil and fuel levels must be checked and all safety guards installed before operating. d. When a new fan drive belt has been installed, check belt tension after first 20 hours of operation. e. Wear protective overalls, and keep items of loose clothing clear of all hot and moving parts. f. Whenever  possible,  clean  components  and  surrounding  area  before  removing  or  disassembling.    Take  care  to exclude all dirt and debris from fuel injection equipment while it is being serviced. g. Some parts are cemented with gasket compound with others being dry.  Before assembly, remove all traces of old gasket and compound.  Take extreme care to exclude dirt from all gasket surfaces and gasket compound from all tapped holes unless otherwise specified. h. It  is  recommended  that  all  oil  seals  are  replaced  once  they  have  been  removed  from  their  original  position.  Seals must  be  installed  square  in  housing  and  all  lip  seals  must  be  installed  with  lip  facing  lubricant  to  be  retained.    A service  tool  should  be  used  to  install  all  oil  seals  and  care  must  be  taken  to  prevent  damaging  new  seal  when  it passes over shafts. i. Replace  all  nuts,  bolts,  capscrews  and  studs  with  damaged  threads.    Do  not  use  a  tap  or  die  to  repair  damaged threads which may impair the strength and closeness of the threads and is not recommended. j. Do not allow grease or oil to enter a blind threaded hole as hydraulic action present when bolt or stud is screwed in could split or stress housing. k. To check or re-torque a bolt or nut, item is slackened a quarter of a turn and then tightened to specified value. I. A  steel  ISO  metric  bolt,  capscrew  or  nut  can  be  identified  by  the  letter  M  either  on  hem  or  one  hexagon  flat.  The strength grade will also be marked on top or one flat. m.   On nuts with identification marks on one face the frictional area of that surface will be reduced, therefore nut should be installed with unmarked face towards component. n. Service   tools   are   designed   to   aid   disassembly   and   assembly   procedures   and   their   use   will   prevent   possible unnecessary damage to components.  It is recommended that service tools are always used, some operations cannot be safely carried out without aid of relevant tool. 3-11