TUBE 3079636 - Caterpillar

Table 1
Required Tools    
Part Number    Description    Qty    
198-4240     Digital Pressure Indicator     1    
6V-9508     Face Seal Plug     2    
6V-8397     O-Ring Seal     2    Test
Illustration 1 g00853523
Main pump (front view) (1) Pressure tap (front pump delivery pressure) (2) Pressure tap (rear pump delivery pressure)
Connect a 34475 kPa (5000 psi) pressure sensor to pressure tap (1) or (2) .
Illustration 2 g00883033
(3) Load sensing line (4) Pressure tap (power shift pressure) (5) Pressure tap (load sensing) (6) Power shift line
Disconnect load sensing line (3) from the pump regulator. Install 6V-8397 O-Ring Seal and 6V-9508 Face Seal Plug in the open end of load sensing line (3) .
Disconnect power shift line (6) from the pump regulator. Install 6V-8397 O-Ring Seal and 6V-9508 Face Seal Plug in the open end of power shift line (6) .
Connect a 3450 kPa (500 psi) pressure sensor to pressure tap (5) .
Connect a 34475 kPa (5000 psi) pressure sensor to pressure tap (4) .
Start the engine. Set the engine speed dial at position 2.Note: The initial standby pressure is 2000 kPa (290 psi) and load sensing pressure is 450 kPa (65 psi) when the oil temperature is 32 °C (90 °F).
Illustration 3 g00883139
(7) Rear pump regulator (8) Adjustment screw (9) Locknut
Mark the position of adjustment screw (8) and locknut (9) .
Loosen locknut (9) .
While you turn adjustment screw (8) clockwise, observe the pressure gauge for the standby pressure.
At approximately 3450 kPa (500 psi) to 3550 kPa (515 psi), the gauge for the standby pressure will fluctuate as the differential relief valve opens. If the pressure fluctuates at a lower pressure, then one of the differential relief valves is faulty.
Turn adjustment screw (8) counterclockwise to the original position.
Repeat Steps 9 through 11 for each engine speed setting up to setting 5.
Adjust the margin pressure to the correct specification. Refer to Testing and Adjusting, "Margin Pressure - Test and Adjust".Replacement of Relief Valve
Note: Replacement of the differential relief valve is not necessary when all of the checked pressures are normal.
Illustration 4 g00839535
Main control valve (1) Differential relief valve (2) Differential relief valveNote: Use a new differential relief valve for replacement when the following problems occur:
Replace differential relief valve (1) when the delivery pressure is normal and all of the following pressures are too low: line relief valves in the stick circuit and line relief valves in the travel circuit.
Replace differential relief valve (2) when the delivery pressure is normal and all of the following pressures are too low: line relief valves in the boom circuit, line relief valves in the bucket circuit and line relief valves in the attachment circuit.