ARMY TM 9-2815-253-24 AIR FORCE TO 38G1-93-2 MARINE CORPS TM 2815-24/3 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 retorque 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 head 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. o. When removing/disconnecting fuel or lubrication lines and coolant hoses cap/cover all openings to prevent entry of foreign material. 3-8