CONNECTION 0814228 - Caterpillar

Illustration 1 g00567807
View from the underside of the machine near the front of the engine
(1) Secondary steering pump
(2) Unloader valve
Illustration 2 g00568158
(1) Secondary steering pump
(2) Unloading valve
(3) Diverter valve
(4) Line from steering hydraulic pump
(5) Line to the hydraulic tank
(6) Relief valve
(7) Line to the steering metering unit If the engine stops or the hydraulic pump fails, the secondary steering system can provide oil in order to operate the steering system. The main components in the secondary steering system are secondary steering pump (1) and unloading valve (2).Secondary steering pump (1) is a ground driven gear pump. The pump turns when the machine moves. The pump is powered by the output transfer gears of the transmission. When the engine is operating, the primary hydraulic pump sends oil through the combination valve. This oil is used to operate the steering cylinders. As the machine starts to move, oil is sent from secondary steering pump (1) to unloading valve (2). When flow is present from the primary hydraulic pump, diverter valve (3) in the unloading valve sends flow from the secondary pump back to the hydraulic tank. The oil supply for steering metering unit (7) comes only from the primary steering hydraulic pump. If the primary hydraulic pump fails, unloading valve (2) will direct oil from secondary pump (1) to the steering metering unit. A flow switch is installed on the combination valve. The switch controls a circuit that is located in the operator compartment which alerts the operator of a pump failure.