TM 10-3930-671-24 NOTE ANY UNUSUAL NOISE Operators    familiar    with    daily    engine    operation    soon become alert to any noise not normally present.  This is very  valuable  in  correcting  defects  in  the  early  stages and preventing expensive repairs or delays. EVERY 50 HOURS 1. REPEAT DAILY OPERATIONS OUTUNED Follow previous instructions. 2. CHANGE CRANKCASE OIL Engine  life  is  dependent  upon  clean  oil  being  circulated to    all    moving    parts;    therefore,    the    frequency    of    oil changes and oil filter replacement  is  very  important  and should be made at regular, scheduled periods. The schedule for changing oil is directly dependent upon the operational environment: an extremely clean operation   could   go   100   hours   while   a   dirty   operation (foundry or cement factory) could be 50 hours or less. Replace   the   oil   filter   element   every   time   the   oil   is changed. Thoroughly  clean  the  sealing  surfaces  before  replacing new element and gasket. Do   not   put   kerosene   into   the   crankcase.      The   best method is to drain the oil when the engine is thoroughly heated-which will carry off most of the sediment. Some operators unwisely put kerosene in the crankcase after  draining  the  engine  oil,  then  turn  the  engine  over with the starter in the belief they are doing a better job of crankcase cleaning. In doing this, kerosene is circulated through the oil pump, the  main  oil  header,  and  the  branches  leading  into  the engine bearings, thereby washing away the protective oil film.    In  addition,  some  of  the  kerosene  will  be  trapped and remain to thin out the new oil, reducing its lubricating qualities. 3. SERVICE AIR CLEANER Clean element with compressed air (See Daily Instructions).  Be sure that no unfiltered air can enter the engine. 4. CHECK FAN BELT TENSION Inspect  wear  condition  of  fan  belt;  note  alignment  and check  belt  tension  which  should  allow  not  over  13ram (1/2") deflection on the long span. 5. CHECK BATTERY WARNING Stop  engine  before  checking  battery terminals   or   electrical   connections. Sparks or flames near a battery could cause  an  explosion  or  fire.    Battery acid     can     cause     corrosive     burns. Always  wear  eye  protection.    Use  of jumper   cables    or    battery    charging should    be    done    only    directed    by manufactures’ safety instructions. Check  specific  gravity  of  each  cell-which  should  be  at feast 1.250.  Add distilled water, if required, to raise level 9.5mm (3/8’) above the separators. Particular   attention   should   be   given   the   battery during cold weather.  The cranking power of a fully charged  battery  @27°C  (80°F)  is  reduced  60%  @  - 18"C  (0°F)but  yet  the  power  required  to  crank  the engine  is  2  1/2  times  greater  at  -18°C  (0°F)  than  0 27°C (80°F). F-165