Case 21F, 121F, 221F, 321F Wheel Loader Repair Manual

Model: Case 21F, 121F, 221F and 321F Tire 4, Tire 4B, Stage 3B
Manuals: Service Manual
Introduction
Engine
Four Wheel Drive System
Front Axle
Rear Axle
Hydrostatic Drive
Brakes and Controls
Hydraulic System
Frames and Ballasting
Steering
Cab Climate control
Electrical System
Front Loader and Bucket
Platform, Cab, Bodywork and Decals
Special Tool Index
Manual Extract: Steering Control

The gear pump, and the variable displacement pump activated by the diesel engine, sucks oil from the oil tank and delivers it to the priority valve . When the steering system is inoperative, the power steering does not send any signal in the form of pressure to the priority valve, therefore delivery oil is available for working attachment.

When the steering is activated, a pressure generates inside the pipe for control delivery, which moves the switching piston of the priority valve.
According the intensity of the signal, the priority valve now sends a higher or lower quantity of oil to the power steering .

Downstream, the steering is ensured by two valves inside the power steering, set at 240 bar (3480 psi). After the activation of the steering cylinder, the oil, through the power steering , and through the return filter , returns to the oil tank .

The check valve allows the power steering to suck oil from the tank, in case of pump fault, thus allowing further movements of the steering
Identify the Tier Level of your Equipment (Read our Article on Tier Level )