BASIC AIR CONTROL VALVE GROUP 8D7306 - Caterpillar

Problem: 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 main control valve and the valve spool have an excessive amount of wear.Problem: The attachment moves while the joystick control lever is in the HOLD position.
Probable causes:
The pilot control actuator on the main control valve is damaged.
The control valve and the valve spool have an excessive amount of wear.
A piston seal in a cylinder has an excessive amount of wear.
There is a leak in a connection between the control valve and the moving cylinder(s).
A load check valve is not closing because of dirt or because of a worn seat.
The control valve is not centering correctly.Problem: The attachment droops when the joystick control lever is moved from the HOLD position to the RAISE position.
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 return spring is weak or broken, or because there is dirt or debris in the load check valve.Problem: The hydraulic force is too low when the joystick control lever is moved to the RAISE position or to the LOWER position.
Probable causes:
The machine is being operated incorrectly.
The pilot system pressure is too low.
The main control valve is contaminated or damaged.
The load check valve is not closing because the return spring is weak or broken, or because there is dirt or debris in the load check valve.
The pilot control valve is contaminated or damaged.
The main relief valve setting is too low.Problem: All implement functions are sluggish.
Probable causes:
The oil level is too low.
The implement pump is worn or damaged.
The main relief valve setting is too low.
The oil in the hydraulic system is contaminated.Problem: The implement functions are erratic or intermittent.
Probable causes:
The oil level is too low.
The implement pump has too much wear.
The main control valve is contaminated or damaged.
The load check valve is not closing because the spring is weak or broken, or because there is dirt or debris in the load check valve.
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 oil suction line between the hydraulic pump and the tank.Problem: There is too much lift cylinder drift.
Probable causes:
The piston seals and/or the lift cylinders are worn.
The components of the main control valve are worn or damaged.
The load check valve is not closing because the spring is weak or broken or because there is dirt or debris in the check valve.Problem: The hydraulic force is too low when the joystick control lever is moved to the TILT BACK position or to the DUMP position.
Probable causes:
The machine is being operated incorrectly.
The settings of the line relief valves