WRENCH 1U6221 - Caterpillar

Illustration 1 g03864624
Schematic of the return system
(1) Blade shutoff valve
(2) Travel motor
(3) Stabilizer shutoff valve
(4) Swivel (main)
(5) Swivel (pilot)
(6) Joystick steering control valve
(7) Steering valve
(8) Quick coupler control valve
(9) VA boom lowering control valve
(10) Boom lowering control valve
(11) Stick lowering control valve
(12) Anti drift valve
(13) Anti drift valve (if equipped)
(14) Multi combination valve
(15) Main control valve
(16) Swing motor
(17) Breather cap
(18) Return filter
(19) Clog pressure switch
(20) Medium pressure pilot pump
(21) Swing pump
(22) Main pump
(23) Engine
(24) Hydraulic fan pump
(26) Hydraulic oil cooler
(27) Hydraulic fan motor
(28) Hydraulic oil tank
(29) Brake valve
(30) Brake safety valve (if equipped)
(31) Pilot manifold
(32) Blade/stabilizer control lever
(33) Left joystick control
(34) VA boom pedal (if equipped)
(35) Right joystick control
(36) Smart boom control valve
Illustration 2 g03747477
(17) Breather cap
(18) Return filter
(19) Clog pressure switch
(28) Hydraulic oil tank
(37) Line from multi combination valve (if equipped)
(38) Line from hydraulic oil cooler
(39) Line from main control valve (port "T")
(40) Line from swing motor and drive case drain
(41) Line from main control valve (port "L") Note: The return hydraulic system consists of various low flow drains as well as high flow return circuits. The low flow drains are typically returned directly to hydraulic oil tank (28). The higher flow return lines are typically filtered before returning to hydraulic oil tank (28).Return filter (18) receives drain oil flow from components through lines (37, 38, 39, 40 and 41). Oil flows through return filter (18) and enters directly into hydraulic oil tank (28).The oil drains directly to hydraulic oil tank (28) from the following components:
Joystick steering valve (6)
Steering valve (7)
Quick coupler control valve (8)
VA boom lowering control valve (9)
Boom lowering control valve (10)
Stick lowering control valve (11)
Standard anti drift valve (12)
Anti drift valve (13)
Brake valve (29)
Brake safety valve (30)
Pilot manifold (31)
Operator controls (32, 33, 34 and 35)
Smart boom control valve (36)The drain oil flow from blade shutoff valve (if equipped) (1) and stabilizer shutoff valve (if equipped) (3) combine with the case drain oil from travel motor (2) and flow to swivel (4). The return oil flow from swivel (4) flows directly to hydraulic tank (28).Case drain oil flow from fan pump (24) and main pump (22) combine and flow to hydraulic oil tank (28) through an internal filter screen.Case drain oil flow from swing pump (21) flows to hydraulic oil tank (28) through an internal filter screen.Case drain oil from fan motor (27) flows to hydraulic oil tank (28) through an internal filter screen.The oil delivery from main pump (22) enters main control valve (15). After the implement oil is sent to the various circuits, the return oil flows back into main control valve (15).Return oil inside main control valve (15) acts against two return check valves. The slow return check valve maintains a constant back pressure. The oil flow through the slow return check valve flows to oil cooler (26). The bypass check valve creates a constant back pressure. The two return check valves are located in the body of main control valve (15). The return check valves maintain a constant pressure in the return line