PLUG 3636423 - Caterpillar

Note: This machine is equipped with a pilot hydraulic system.Some terms and the definitions
Collapse is a sudden drop of a cylinder during normal operation.
Drift is a slow or creeping motion of the implement cylinders with the implement controls in the hold position.
Droop is an initial movement of the hydraulic cylinders in the direction opposite the direction commanded by the operator. The cylinders then move in the correct direction.Problem 1: The pump makes noise and the cylinder rods do not move evenly. There are also air bubbles in the oil.Probable causes:
The viscosity of the oil is incorrect.
The main relief valve opens at low oil pressure.
The implement pump has too much wear. Problem 2: The oil temperature is too high.Probable causes:
The machine is being operated above the intended capacity or in ambient temperatures that are too high for the machine's design.
The viscosity of the oil is incorrect.
The setting of the main relief valve is too low. This will cause the relief valve to open.
The implement pump has too much wear.
There is a restriction in an oil passage.
There is a leak in one or more circuits.
The load on the system is too high. This causes the relief valve to open.
The oil level is low.
The oil is contaminated.
The air flow through the oil cooler is too low.
The oil flow through the oil cooler is too low.
There is air in the hydraulic oil. Note: A problem with air in the hydraulic oil must be corrected before the hydraulic system will operate at normal temperatures. There are two conditions that cause air to be in the hydraulic oil:
Return oil is flowing into the hydraulic oil tank above the level of oil that is in the tank.
There are leaks in the lines between the implement pump and the hydraulic tank.
The hydraulic oil temperature sensor is faulty. Problem 3: The pump output is low.Probable causes:
The oil level is low.
The viscosity of the oil is incorrect.
The pump has too much wear. Problem 4: The oil pressure is low.Probable causes:
The main relief valve opens at low oil pressure.
The implement pump has too much wear.
An O-ring seal in the system failed.
The control valve and the valve spool have excessive wear. Problem 5: The attachment moves while the control lever is in the HOLD position.Probable causes:
The control valve and the valve spool have excessive wear.
A piston seal in a cylinder has excessive wear.
There is a leak in a connection between the control valve and the drifting cylinder(s).
A check valve is not closing because of dirt or because of a worn seat.
The control valve is not centering correctly.
The control levers are not in the center position when the engine start key was turned to the ON position. There may be dirt or the return spring may be broken. Problem 6: The attachment droops when the lift control lever is moved from HOLD to RAISE.Probable causes:
The oil is too cold.
The piston seals and/or the lift cylinders are worn.
The load check valve is not closing because the spring is weak or broken or