TM 10-3930-669-20 WARNING · High-pressure   hydraulics   [oil   under   3,000   psi   (20,700   kPa)   pressure]   operate   this equipment.      Refer   to   vehicle   operator   and   maintenance   manuals   for   hydraulic   oil pressure.  Never disconnect any hydraulic line or fitting without first dropping pressure to zero.  Failure to comply may result in injury to personnel. · Hydraulic oil is slippery and can cause falls.  To avoid injury, wipe up spilled oil with rags. VISUAL INSPECTION Inspect stack valve. (a) If stack valve is damaged or leaks, notify DS Maintenance. (c) If stack valve is not damaged and does not leak, stack valve is OK. VISUAL INSPECTION (1) Remove cab floor plate (Para 15-12). (2) Inspect     reservoir     return     hoses     and fittings   from   steering   control   pump   to priority valve to stack valve to hydraulic filter   to   reservoir   for   looseness   and damage. (a) If  hose  fittings  are  loose,  tighten fittings. (b) If hose(s) and/or fittings are damaged,  replace  hose(s)  and/or fittings (Para 17-10). (c) If   hoses   and/or   fittings   are   not loose or damaged, hoses are OK. (3) Close right-hand engine access cover. (4) Install cab floor plate (Para 15-12). 2-479