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

Table of Contents

• Content
• 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 )