TM 10-3930-671-24 METHOD 2 - Fluid Change NOTE If    old    oil    is    excessively    dirty    or hydraulic  system  contaminated,  refer to METHOD 1 procedures for draining and flushing tank. 1. Locate the hydraulic system pressure diagnostic check port. 2. Remove the snap-on cap and connect a suitable drain hose line to the diagnostic check port.  Use quick-disconnect  adapter  fitting,  Clark  Part  No. 3797029. NOTE You  will  need  a  drain  pan  of  5.5  gal minimum   capacity,   or   other   method of   disposal,   for   collecting   the   used oil.      Be   sure   the   outlet   end   of   the drain line is directed into the pan and held from moving when pressurized. 3. With   direction   control   in   NEUTRAL,   start   the engine and let it run at idle speed to operate the main hydraulic pump.  Do not accelerate engine speed.  A steady stream of used oil should flow from the drain line. 4. Continue  operation  until  sump  tank  is  emptied. This point will be reached when the pump starts to   cavitate.      When   cavitation   occurs   you   will notice a change in the sound of the pump.  Also, watch  the  drain  line.    The  oil  flow  will  become erratic or will stop when the pump can no longer pick up oil from the sump tank. CAUTION Be    careful    when    sump    is    nearly emptied.    Watch   for   signs   of   pump cavitation.  Do not operate pump after cavitation occurs or damage to equipment may occur. 5. Stop the engine.  Turn key switch OFF as soon as pump cavitation is noted. 6. Disconnect  drain  hose  from  the  truck.    Replace cap on the hydraulic pressure check port fitting. 7. Remove and discard used oil filter.  Install a new hydraulic oil filter. 8. Remove the used sump tank fill cap/breather. F-452