TUBE ASSEM. (oil drain) 6N6120 - Caterpillar

Illustration 1 g00631699
Secondary steering schematic (1) Check valve. (2) Diverter valve. (3) Check valve. (4) Secondary steering pump. (5) Relief valve. (6) Pressure control valve. (7) Pressure switch. (8) Pressure reducing valve. (9) Main relief valve. (10) Shuttle valve. (A) Suction line. (B) Return line. (C) Pressure line from the main steering pump. (D) Reduced pilot oil pressure. (E) Load sensing line. (F) High pressure oil line.
Illustration 2 g00631765
Location of the secondary steering pump (4) Secondary steering pump. (7) Pressure switch. (A) Suction hose. (B) Tank line. (C) Steering pressure. (F) Supply hose to steering control valve.The secondary steering pump is ground driven. The machine must be moving in order for the secondary steering system to operate. The secondary steering pump is located on the front of the transfer case housing.Under normal conditions, high pressure oil from the main steering pump is sent through line (C). This high pressure oil passes through check valve (3). The high pressure oil can then travel to the steering control valve. The high pressure oil forces the diverter valve (2) downward. This diverts oil from secondary steering pump (4) to the hydraulic oil tank. Check valve (1) prevents the high pressure oil from the main steering pump from flowing to the secondary steering pump. Secondary steering pump (4) is always supplying oil when the machine is moving. Relief valve (5) keeps the secondary steering oil pressure below 17300 kPa (2509 psi).
Illustration 3 g00803195
High pressure oil from the main steering pump passes through pressure control valve (6) and presses on pressure switch (7). When the steering oil pressure drops, pressure switch (7) sends a warning to the operator that primary steering system pressure is lost. An indicator (11) in the cab indicates that the primary steering system has failed and the secondary steering system is being used. An action alarm will also sound.When the main steering pump fails, oil pressure that is in load sensing line (E) drops. This allows diverter valve (2) to shift into the closed position. When the diverter valve is in the closed position, oil from secondary steering pump (4) flows through check valve (1) to the steering control valve. Oil from the secondary steering pump then flows to the spool valve. The main relief valve (9) still limits the system pressure to 27600 kPa (4003 psi).The secondary steering pump can also supply pilot oil if the pilot oil pump fails. High pressure oil is sent through pressure reducing valve (8). The pressure reducing valve drops the high pressure oil to the pressure level of the pilot oil system. Pilot oil line (D) flows to the pilot control valve.