TM10-3930-660-20 18-6. MAIN CONTROL VALVE ASSEMBLY - ADJUST/REPLACE (Cont’d) 4. PURGE AIR FROM HYDRAULIC CIRCUIT. a. Start engine, TM10-3930-660-10. b. Cycle boom hoist and extend functions five times. C. Shut off engine and check for leaks, TM10-3930-10. 5. INSTALL TRANSMISSION COVER, PARA.  16-6. ADJUSTMENT  -  MAIN RELIEF VALVE Adjustment of main control valve assembly is limited to adjustment of relief  valves. There are a total of four relief valves on the main control valve  assembly. 1. CONNECT PRESSURE GAUGE TO VALVE PORT. a. b. c. d. Remove main relief valve plug assembly  (l). Connect O to 5000 psi pressure gauge to plug assembly port (2). Start  engine. TM10-3930-660-10. Operate boom hoist, lower, extend, or retract function until cylinder bottoms out and hydraulic oil is passing over relief valve. Continue to hold hydraulic lever in that position so oil passes over relief valve during relief valve adjustment. Engine may be operated at idle or full throttle when performing tests/ adjustments. 2.   READ RELIEF VALVE PRESSURE ON GAUGE. PRESSURE RANGE IS 2,750 to 2,850 psi. IF RELIEF VALVE PRESSURE IS NOT WITHIN SPECIFICATIONS, ADJUST AS FOLLOWS: 18-20