TUBE AS 4388840 - Caterpillar

Illustration 1 g00530811
Pressure Control Valve
(1) Charge pump port
(2) Cooler port and charge filter port
(3) Spring
(4) Passage
(5) Makeup valve spool
(6) Passage
(7) Check valve
(8) Implement control valve port
(9) Passage
(10) Passage
(11) Chamber
(12) Drain passage
(13) Relief valve
(14) Spring
(15) Nut
(16) Cold oil relief valve
(17) Retainer
(18) Tank return passage
(19) Cooling orifice
(20) Tank return port
(21) Return port from steering pilot valve
(22) Return port from steering motor case
(23) Supply port to steering motor case
(24) Return port from steering pump case The pressure control valve is located under the steering pump and to the left of the torque converter. The valve provides a cold oil relief valve (16), a makeup valve (5), and cooling orifice (19).Cold oil relief valve (16) protects the cooler and the charge filter from high pressures. The pressure setting of the valve is approximately 2200 kPa (320 psi). During normal operating conditions, oil from the charge pump enters port (1), flows through passage (10), and through port (2). The oil then flows to the cooler and the charge filter. The pressure of the oil in passage (1) is against pilot valve (13). The force of spring (14) keeps pilot valve (13) closed when the pressure is less than the setting of the relief valve.When the pressure in passage (10) and the charge line pressure reaches the relief valve setting, pilot valve (13) opens. Oil flows around pilot valve (13), into chamber (11) and through drain passage (12) to tank return passage (18). An increase or a decrease in the force of spring (14) changes the relief valve setting. Loosen nut (15) and turn retainer (17) clockwise in order to increase the setting. Turn the retainer counterclockwise in order to decrease the setting.The makeup valve is a pressure reducing valve. The valve protects the charge circuit from low pressure. Also, the valve adds makeup oil to the steering circuit. The pressure setting of the valve is approximately 1360 kPa (200 psi). During normal operating conditions, the charge pump flow enters port (1), flows through passage (10), and exits through port (2). Then, the oil flows to the cooler and the charge filter. The pressure of the oil in passage (1) also flows through passage (4), around makeup spool (5), and through passage (6). Then, the oil moves the spool against spring (3). The spool shuts off makeup flow from the implement control valve. When the pressure of passage (10) decreases and the pressure reaches the setting of the makeup valve, makeup spool (5) opens. The makeup valve meters the flow from the implement control valve. The oil enters port (8), flows through check valve (7), and through passage (9). Then, the oil flows into the charge circuit.Cooling orifice (19) provides additional flow to the motor case in order to help cool the case. Steering pump case flow enters port (24). Most of the oil flows around cooling orifice (19) and into tank return passage (18). Some of the oil exits port (23) and flows to the motor case. Return flow from the motor case enters