TM10-3930-660-20 18-3. HYDRAULIC SYSTEM - SERVICE (Cont‘d) PURGING AIR FROM PISTON PUMP To prevent internal damage to piston pump (1) be sure pump housing is filled with oil before beginning purging procedures. The piston pump (1) supplies hydraulic pressure to the MLRS attachment cylinder assembly, to the carriage tilt cylinders, and to the fork sideshift cylinders. 1. PURGE AIR FROM PUMP a. Loosen but do not from reducer (3) a (1). remove hose (2) t tee (4). place suitable container under pump (1) to catch any oil lost during the purging process. b. Place auxiliary fuel shut-off switch in the "off” position, TM10-3930-660-10. NoTE A solid stream of fluid will flow out of loosened hose (2) when air is purged from pump (l). c. d. Crank engine until solid stream of fluid is flowing from hose (2) at reducer  (3). While continuing to crank engine, have assistant tighten  hose  (2). Stop cranking engine. Place auxiliary fuel shut-off switch the ‘on” position, TM10-3930-660-10. 18-3