TM 10-3930-671-24 Hydraulic System Fluid and Filter Change NOTE It is recommended to: • Drain  and  replace  the  hydraulic  sump fluid   every   2000   operating   hours,   or once a year. • Replace the hydraulic oil filter every 500 hours and at each oil change. • Replace  the  sump  tank  breather/fill  cap every 500 operating hours. There   is   no   drain   plug   in   the   hydraulic   sump   tank. Unless  the  sump  tank  is  to  be  removed  for  other  repair or  maintenance,  the  hydraulic  fluid  can  be  changed  by using one of the following methods: METHOD   1.      Removal   of   the   hydraulic   sump   cover assembly  and  pumping  the  fluid  out  by  suction  using  a separate pump and hose.  This method should be used when  the  hydraulic  fluid  is  severely  contaminated,  e.g., after a pump or other major hydraulic component failure. METHOD  2.    Pumping  the  fluid  out  by  using  the  truck hydraulic system.  This method may be used most easily and  satisfactorily  for  routine  changes  of  the  fluid.    Both methods are described below. NOTE To perform this service procedure, it is recommended that you first: • Park truck on a level surface. • Put the upright in a vertical position and lower the carriage fully down. • Return  all  controls  to  neutral  and  turn key   switch   OFF,   except   as   otherwise directed. • Apply  the  parking  brake  and  block  the wheels. Open the engine compartment for access to main valve, sump tank fill cap/breather and oil filter. METHOD 1 Fluid Change 1. Loosen  the  sump  tank  cover  clamping  ring  and remove  the  cover  assembly  and  seal  from  the tank.    Store  temporarily  in  a  manner  to  keep  it from  being  damaged  or  contaminated  with  dirt (Suggestion: Wrap with clean plastic). 2. Insert suction hose from the separate pump into the sump tank to pump out the hydraulic fluid (or use a siphon hose to drain the fluid from tank). NOTE If   old   oil   is   extremely   dirty,   it   is advisable to flush the tank with clean oil to remove all contaminants. 3. Examine  the  screen  in  the  cover  assembly.    If dirty, it should be cleaned thoroughly. 4. Reinstall the sump cover assembly.  Be sure the seal is properly seated.  Tighten clamping ring. 5. Refill   sump   tank   with   recommended   fluid   and replace   filter   and   breather   cap   as   noted   after Method 2 description below. Hydraulic Sump Tank Capacity, Useable Volume: 5.5 gal (20.82 L). F-451