TM10-3930-660-20 18-13. BOOM CYLINDER FLOW CONTROL VALVE - REPLACE This task covers: a. Removal b. Installation Initial Setup Tools Materials/Parts Tool Kit, Automotive Mechanics Container, 1 Gal. Tags (App. C, Item 51) Cap and Plug Set Reference Equipment  Condition TM10-3930-660-10 Vehicle parked on level ground. Boom fully lowered and MLRS attachment resting on ground. Transmission cover removed, para.  16-6. REMOVAL Hydraulic oil in the system can be under pressures over 3000 psi with the engine OFF . ALWAYS relieve pressure in hydraulic lines before attempting to remove any component in the hydraulic system. With engine OFF, starter switch in RUN position, and MLRS attachment on the ground, move control levers through all operating positions several times to relieve line pressure. Relieve pressure in hydraulic oil tank by loosening filler cap very slowly.   Failure to follow these precautions could result in serious personal injury. WARNING  _ When working underneath the boom, always support the boom using blocks, jackstands, or other rigid and stable supports. Combined weight of boom and MLRS attachment is approximately 6300 pounds. Failure to adequately support the boom could result in severe injury or death. CAUTION Wipe the area clean around all hydraulic connections to be opened during removal and disassembly. Cap out lines and plug holes after removing lines. Contamination of the hydraulic system could result in premature failure. At operating temperatures, hydraulic oil is hot and under pressure. Hot oil can cause  injuries. Allow hydraulic oil to cool before disconnecting any hydraulic lines. 18-51