ENGINE AR-PRIMARY 4244164 - Caterpillar

Return Hydraulic System
The oil delivery from the drive pump and the idler pump enters the main control valve. The oil then flows through the return passage onto the hydraulic tank in the following manner.When all joysticks and/or travel levers/pedals are in the NEUTRAL position, pump low pressure standby oil from drive pump flows through internal passages and the bypass cut spool to the return passage. Pump low pressure standby oil from idler pump flows through internal passages and the bypass cut spool to the return passage. From the return passage, the return oil flows through slow return check valve, hydraulic oil cooler, and returns to the hydraulic tankWhen any one of the joysticks and/or travel levers/pedals is shifted from the NEUTRAL position, bypass cut spools shifts to the closed position. Pump oil is then directed to the cylinders and/or motors. The return oil from the cylinders and/or motors now flows through the cylinder-to-tank spool or motor-to-tank spool and returns into the internal passages. From return passage the return oil flows through slow return check valve, hydraulic oil cooler, and returns to the hydraulic tank.Other components of the return system include:
Slow return check valve
Bypass check valve
Hydraulic oil cooler
Hydraulic tank and filter
Case drain filterNote: Refer to the appropriate sections in this manual for more information.