PLUG, TUBE 26570026 - Caterpillar

Introduction
Note: Run the tests for the machine control module before troubleshooting the hydraulic system. Check the event list on the Caterpillar Monitoring System before you troubleshoot the hydraulic system.
Correct oil flow and pressure are necessary for correct operation. Pump output, or the oil flow is dependent on the engine speed. Oil pressure is caused by resistance to the oil flow.
Always warm the hydraulic oil to a minimum temperature of 50°C (122°F) before starting any testing and adjusting procedure.
Use the following engine speeds during testing.Low Idle ... 700 20 rpmFull Load ... 1745 5 rpmHigh Idle ... 1850 20 rpm
The implement and travel control valve is composed of single control valve spools. The spools are the stick, the boom, the bucket, the left track, and the right track. The implement and travel control valve is supplied with hydraulic oil from the three implement piston pumps.
Each of the implement circuits has a check valve which prevents cylinder drift during spool movement. Each implement circuit has makeup valves. The makeup valves allow the flow of oil to both ends of the cylinders and the motors. There is also a line relief valve for each of the circuits.
Main hydraulic system pressure is controlled by the load sensing signal relief valve. The load sensing signal relief valve has two settings. The load sensing signal relief valve is set at 32000 500 kPa (4650 72 psi) for the implement circuit. The load sensing signal relief valve is set at 35000 500 kPa (5080 75 psi) for the travel circuit.
A load sensing signal relief valve that is set too low can result in reduced forces for the implements and in increased cycle times.
The three margin relief valves are located on the discharge ports of the hydraulic piston pumps. The margin relief valve is set to open when the discharge pressure of the implement piston pump is 2930 kPa (425 psi) above the load sensing pressure.
During individual circuit operation, a line relief valve that is set too low may result in the following problems: increased cycle times, excessive heat in the hydraulic system, poor performance and noise from the opening and closing of the line relief valve. The line relief valves for the boom circuit, the stick circuit and the bucket circuits are set to open at 34000 350 kPa (4930 50 psi). The line relief valves for the travel circuit are set to open at 38000 700 kPa (5515 100 psi).
The spools for the implement and travel control valve are actuated by pilot system pressure from the implement pilot valves. The travel spools are actuated by pilot system pressure from the travel pilot valves. The pressure in the pilot system is regulated by the low pressure pilot relief valve.
Swing system pressure is set by the swing