HOSE 7W4852 - Caterpillar

Hydraulic Schematic For Return Circuit
Illustration 1 g00704221
(1) Swing motor (2) Travel motors (3) Drain line (swing) (4) Drain line (travel) (5) Makeup line (6) Return passage (7) Main control valve (8) Center bypass passage (9) Orifice (10) Orifice (11) Drain line (12) Center bypass passage (13) Return line (14) Upper pump (15) Pilot pump (16) Drain filter (17) Slow return check valve (18) Oil cooler (19) Return filter (20) Hydraulic tank (21) Lower pump (22) Bypass check valve (23) Suction line (24) Return line (25) Drain line (26) Return lineIntroduction
The oil from upper pump (14) and lower pump (21) enters the main control valve. The oil then flows to return passage (6) in one of the following manners.There is no load on the machine.
Upper pump oil flows into center bypass passage (8) and orifice (9) to return passage (6) .
Lower pump oil flows into center bypass passage (12) and orifice (10) to return line (13) .
Return oil from each control valve for travel, swing and implements flows to return passage (6) .The oil from return line (13) flows through return passage (6) and slow return check valve (17). The oil then flows to the hydraulic tank in the following manner.
With very low oil temperature, most of the oil is returned through bypass check valve (22) to hydraulic tank (20). The remainder of the oil flows into oil cooler (18) and return filter (19) to hydraulic tank (20) .
When the oil temperature increases, the rate of oil flow through bypass check valve (22) decreases. This causes the rate of oil flow through oil cooler (18) to increase.Case drain oil from swing motor (1) and travel motors (2) flows into respective drain lines (3) and (4), and combines at drain line (11). The oil then returns to hydraulic tank (20) through case drain filter (16) .If a vacuum occurs in the swing motor, makeup line (5) will route oil to the inlet of the motor. Routing oil to the inlet of the motor will eliminate the vacuum condition.Components In Return Circuit
This section contains the description on the construction and operation of the following return circuit components.
Oil cooler (18)
Bypass check valve (22)
Return filter (19) and hydraulic tank (20)
Drain filter (16) Slow Return Check Valve And Oil Cooler
Illustration 2 g00474329
Main control valve compartment (return circuit) (5) Makeup line (7) Control Valve (13) Return line (17) Slow return check valve (24) Return line
Illustration 3 g00474330
Rear view of cab (24) Return line (25) Inlet line to oil cooler (18) (26) Return line (27) Block (built-in bypass check valve (22) )
Illustration 4 g00474331
Oil cooler (18) Oil cooler (25) Inlet line to oil cooler (18) (28) Outlet line (oil cooler to the hydraulic tank)Slow return check valve (17) is contained in return line (24). Slow return check valve (17) restricts the oil flow which causes a pressure increase in return line (24). Oil from return line (24) flows into makeup line (5). This removes the vacuum condition in the swing motor.Note: For more information on the makeup operation,