LINER 2652491 - Caterpillar

Hydraulic oil pressure can remain in the hydraulic system on this machine after the engine and pump have been stopped. Serious injury can result if this pressure is not released before any service is done on the hydraulic system. In order to prevent possible injury, release the hydraulic system pressure before working on any fitting, hose, or hydraulic component.Lower all work tools to the ground before service is started. If the hydraulic system must be serviced, tested, or adjusted with the work tool in the raised position, the work tool and lift cylinders must be supported properly.Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are being made.
Required Tools
Illustration 1 g00995714
Table 1
Required Tools    
Tool     Item     Part Number     Description     Qty    
A     A1     6V-4143     Coupler     2    
A2 6V-3989     Fitting     1    
A3 8T-0861     Pressure Gauge (60000 kPa (8700 psi))     1    
A4 177-7860     Hose As     1    Procedure
Illustration 2 g01007140
Connect tooling (A) to pressure tap (B) .
Do not stall the implements during hydraulic system warm-up. Stalling the implements causes oil to flow across the relief valve. This can damage the vane-type hydraulic pump when the system is cold. Before you allow the implements to stall, wait until the hydraulic system reaches operating temperature.
Start the engine and raise the temperature of the oil to normal operating temperature.
Raise the lift arms as far as possible.
Increase the engine speed to HIGH IDLE. Observe the pressure gauge and move the control lever to the full RAISE position. Stall the cylinder at the end of the stroke for 5 seconds or less. The high reading on the pressure gauge is the pressure setting of the main relief valve. The correct pressure setting of the main relief valve is 24000 350 kPa (3480 50 psi).Note: Do NOT stall the cylinders for more than five seconds.
Illustration 3 g01007143
(1) Implement pump body (2) Main relief valve
Illustration 4 g01007145
(2) Main relief valve
If a pressure change is required, lower all of the work tools to the ground and stop the engine. The main control valve body (2) can be reached through the floorplates in the cab. For instructions on removing and installing the floorplates, refer to the Disassembly and Assembly manual for your machine. Move all control levers to all positions in order to release any pressure that is trapped in the cylinders. Slowly remove the cap on the hydraulic tank in order to relieve any tank pressure.
Loosen jam nut (3) on the retainer assembly.
Turn retainer assembly (4) clockwise with an allen wrench for an increase in the pressure setting of the main relief valve.Turn retainer assembly (4) counterclockwise with an allen wrench for a decrease in the pressure setting of the main relief valve.Note: One full turn of the retainer assembly will