How to Test and Adjust the Caterpillar 320C Excavator Pilot Relief Valve
(1) Park the machine on flat ground.
(2) Turn off the engine.
(3) Release the pressure of the hydraulic system, refer to the “Pressure Relief of the Hydraulic System” section.
(4) As shown in Figure 2-3-169, connect a 6000kPa pressure gauge to the pressure measuring joint 30.
(5) Start the engine.
(6) Set the machine control volume as follows: the engine tachometer is set to 10, and the AEC switch is set to OFF. See the “Engine Performance Testing” section for engine RPM settings.
(7) Increase the hydraulic oil temperature to (55 ±5)°C.
(8) Check the setting of the pilot safety valve at pressure measuring joint 30.
(9) The pilot safety valve should be set at (4100 ± 200) kPa. If the setting is not within specifications,
adjust the pilot relief valve.
(10) To adjust the pilot relief valve, loosen the locknut 28.
(11) Rotate the set screw 29 until the pressure gauge connected to the pressure test joint 30 reads
(4100
± 200) kPa. NOTE: Turn the set screw 29 clockwise to increase the pressure; turn the set screw 29
counterclockwise to decrease the pressure. Always make final pressure adjustments as pressure
increases.
(12) Tighten the lock nut 28 so that the tightening torque is (49±4.9) N.m. Note: The engine and pump
are required to be running properly to make pressure adjustments. If the pressure adjustment is not
correct, check the characteristic curves of the engine and pump.
13. Test and adjustment of the main safety valve (1) Park the machine on a flat ground and turn off the
engine. (2) Release the pressure of the hydraulic system. See “Pressure Relief of Hydraulic System”
