PLATE 1293032 - Caterpillar

Do not adjust the main relief valve above the specified pressure. Adjustment of the main relief valve above the specified pressure may cause damage to the gear pump.
Perform the main relief valve test in order to determine if the main relief valve for the work tool is damaged or improperly set.
Engage the parking brake. Stop the engine.
Raise the cab. Refer to Operation and Maintenance Manual, "Cab Support Operation" for the proper procedure.
Illustration 1 g01055240
(1) Test port
Connect one end of the 177-7861 Hose to the test port (1) for the work tool. Connect the 8T-0860 Gauge to the other end of the 177-7861 Hose .
Route the test hose so that the cab will not rest on the hose. Securely bolt the cab to the frame.
Sit in the operator's seat. Fasten the seat belt. Lower the armrest. Start the engine. Disengage the parking brake.
Set the engine to HIGH IDLE.
Illustration 2 g00788651
Pilot operated hydraulic control ( work tool)
Move the pilot operated control lever for the work tool to the full LOWER position. Hold the control lever until the lift arms are fully lowered and a stall condition exists. Note: Do not stall the hydraulic system for more than 10 seconds. If necessary, release the work tool from the stall condition. Release the work tool for 30 seconds and repeat the following step.
Record the system pressure for the work tool during the stall condition. Move the control lever for the work tool to the NEUTRAL position.
Table 2
MAIN RELIEF PRESSURE    
Machine     Main Relief Pressure    
267B/ 277B/ 287B    
23000 700 kPa (3336 102 psi)    
287B (1)    
23000 1000 kPa (3336 145 psi)    
( 1 ) HF XPS
Release the hydraulic control from the stall condition. Tilt the work tool until the work tool is parallel with the ground. Stop the engine.
If the pressure reading is within specifications, proceed to step 22. If the pressure reading is not to specifications, the main relief valve needs to be adjusted. Proceed to step 11. For machines equipped with High Flow XPS, if the pressure is not within specifications, proceed to Testing and Adjusting, "High Flow Hydraulic System - Test and Adjust (if equipped)".
Release the hydraulic system pressure. Refer to Testing and Adjusting, "Hydraulic System Pressure - Release" for the proper procedure.
Raise the cab of the machine.
Illustration 3 g01383119
Main relief valve for the work tool
Illustration 4 g01355287
(2) Main relief valve for the work tool (Type 1) (3) Cap (4) Locknut
Remove end cap (3) from main relief valve (2) .
Loosen locknut (4) . The adjustment screw is under the end cap (3) . Turn the adjustment screw clockwise in order to increase the relief valve setting. Turn the adjustment screw counterclockwise in order to decrease the relief valve setting.
Tighten locknut (4) and install cap (3) .
Lower the cab and repeat steps 5 through 10.
Illustration 5 g01383119
Main relief valve for the work tool
Illustration 6 g01355281
(5) Main relief valve for the work tool (Type 2) (6) Locknut (7) Adjusting nut
To adjust the relief valve pressure, hold