TM10-3930-660-20 18-7. MLRS  ATTACHMENT  CONTROL VALVE ASSEMBLY - REPLACE (Cont'd) 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. 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. CAUTION Wipe the area clean around all hydraulic connections to be opened during removal and disassembly. Cap oil lines and plug holes after removing lines. Contamination of the hydraulic system could result in premature failure. If more than one hydraulic line is to be removed, identify lines to assure proper installation.  Use  suitable  container  to catch any hydraulic oil that may drain from  system. 18-30