PIN-YM 4181945 - Caterpillar

Bench Test
Lower all attachments to the ground.
Stop the engine. Move the hydraulic control levers to all positions so that the pressure in the hydraulic system is released.
Relieve the pressure in the hydraulic tank.
Remove the relief valve that needs to be tested.
Install the relief valve in the manifold.
Connect the manifold to the hydraulic test bench.
Slowly increase pressure. Note the pressure when the relief valve opens. Make an adjustment to the relief valve, if necessary.Relief Valve Adjustments
Illustration 5 g00483359
Typical Combination Line Relief and Makeup Valve (4) Cap (5) Locknut (6) Adjustment Screw
Remove protective cap (4) .
Loosen locknut (5) .
Turn adjustment screw (6) clockwise for an increase in the pressure setting. Turn adjustment screw (6) counterclockwise for a decrease in the pressure setting.
After screw (6) is turned for an adjustment, tighten locknut (5) and test the adjustment.
Install cap (4) after the setting is correct.Troubleshooting
Problem List
Problem List for the Hydraulic Pump and the Hydraulic System
(A) The temperature of the oil is too high.
(A) The pump makes unusual noise. The cylinder rods do not move smoothly and there are air bubbles in the oil.
(A) There is a large amount of air in the oil.
(A) The setting for low pressure standby is too low.
(A) The setting for low pressure standby is too high.
(A) The margin pressure is too low.
(A) The margin pressure is too high.
(A) Pump discharge pressure is too high.
(A) Pump discharge pressure is too low.
(A) There is a pause before pressure is reached in all circuits.
(A) Signal pressure is not zero when all valves are in the HOLD position.Problem List for the Equipment System
(B) Any attachment moves with the control levers in the HOLD position.
(B) The control stem on a valve will not shift into the body.
(B) The attachments exhibit excessive drift.
(B) The attachments droop when the attachments are raised.
(B) The cycle times of the attachments are too slow.
(B) The bulldozer blade moves upward. This occurs with the control lever in the HOLD position.
(B) The cycle times of the attachments are too fast.
(B) There is too long of a pause at ground level before the bulldozer starts to raise.
(B) The line relief valves are too noisy.Probable Cause List
Probable Cause List for the Hydraulic Pump and the Hydraulic SystemProblem 1. (A)The temperature of the oil is too high.Probable Cause
Wrong oil viscosity
Excessive wear in the pump
Restriction in an oil passage
Excessive load on the system
Oil aeration
Low oil level
Wrong setting of flow compensator valve
High outside air temperatureProblem 2. (A)The pump makes unusual noise. The cylinder rods do not move smoothly and there are air bubbles in the oil.Probable Cause
Wrong oil viscosity
Oil aeration
Excessive wear in the pump
Low oil levelProblem 3. (A)There is a large amount of air in the oil.Probable Cause
Oil aeration
Low oil level
Leakage around cylinder sealsProblem 4. (A)The setting for low pressure standby is too low.Probable Cause
Wrong setting of flow compensator valve
Broken spring in flow compensator valve
Malfunctioning pump
Wrong setting of pressure compensator valve
Broken spring in pressure compensator valveProblem 5. (A)The setting for low pressure standby is too high.Probable Cause
Wrong setting of flow compensator valve
Signal pressure above zeroProblem