824 TRACTOR Brakes Caterpillar

1.1. Bleeding Wheel Brakes
2.1. Bleeding Brake Accumulator Cylinder and Brake Control Valve:

The wheel brakes are hydraulic expanding tube-type. They are actuated by oil pressure, supplied by the hydraulic steering system to an accumulator which in turn supplies pressure oil to the brake valve in excess of actual need. This excess oil pressure will permit five complete braking stops should the engine stop or the steering system pump fail. Pressure oil from the brake valve is modulated to the brake adjusting valve, one at each wheel brake. The brake adjusting valve applies the brakes and retains sufficient oil in the expanding tubes so that the brake actuating time is at a minimum and the wheel brakes are automatically adjusted.

The wheel brakes should be inspected periodically for lining wear and also to see that the retracting springs (1) are in serviceable condition and that none are broken or lost. Broken or missing springs should be immediately replaced. See your AVSpare dealer.

To inspect for lining wear, apply the brakes and observe the shoe plate (3). As the brake lining (2) wears, the shoe plate (3) will move farther out against the tension of the retracting spring (1). When the brake lining (2) has worn enough to permit the shoe plate (3) to contact the retracting spring (1) at the edge of the plate, new brake shoes should be installed.

1-Retracting springs. 2-Brake lining. 3-Shoe plates.

Brake Accumulator Cylinder

The brake accumulator cylinder is lubricated with oil and charged with dry nitrogen gas under pressure when assembled. No periodic lubrication is required.

Check the accumulator precharge pressure every 500 service hours. See your AVSpare dealer.


Shipment by any means on land of any gas compressed to more than 40 PSI is controlled by the Interstate Commerce Commission within or between states and by the Coast Guard for shipment on any waterway. Areas outside the United States may be controlled by other regulations. The brake accumulator cylinder charging is such that Interstate Commerce Commission and Coast Guard permits regarding shipment of compressed gases must be obtained before transporting the machine or a cylinder charged to more than 40 PSI, by any method. See your AVSpare dealer for more information about permits.

The Transportation Information Plate is located in full view of the operator.


Bleeding Wheel Brakes

Whenever there is more than a 1 second delay in wheel brake application or the wheel brakes are not fully releasing or dragging the brake system should be bled as follows:

Bleeding Brake Accumulator Cylinder and Brake Control Valve:

Whenever air enters the brake control valve or lines during servicing of the machine, the valve may chatter when the brake pedal is depressed. When valve chatter, which is a loud, vibrating sound, occurs, bleed the air from the valve. To bleed the brake control valve and accumulator cylinder:

1. Start the diesel engine to charge the accumulator cylinder with oil.
2. Stop the engine when the cylinder is fully charged. Full charge is indicated by a reading of approximately 1600 PSI on the gauge.
3. Using a light pressure, depress the brake pedal slightly and loosen the brake control valve bleed plug (1) not more than two turns. If pressure does not immediately relieve, the seal on the plug may be sticking. The seal may be loosened by hydraulic pressure or by tightening and again loosening the plug.
4. Tighten the bleed plug when oil flows out without air bubbles.
5. Apply and release the brakes several times until the pressure is exhausted from the accumulator cylinder.

Repeat steps 1, 2 and 5 three times before bleeding the wheel brakes. It may also be necessary to repeat steps 3 and 4 one or more times to bleed all air from the brake control valve. This should be done if the valve chatters.

1-Bleed plug.

Bleeding Wheel Brakes:

To keep the fluid off the braking surfaces, attach a hose (2) to each bleeder valve.

1. With the diesel engine running at low idle speed, open bleeder valve (1) and apply the wheel brakes until oil flows continuous and contains no air bubbles. Close the bleeder valve.
2. Repeat this procedure for each wheel brake. Approximately one-half gallon of oil should be flushed from each bleeder valve.

1-Brake bleeder valve. 2-Hose.

3. Apply the brakes, holding the pedal down for 10 seconds. Repeat this three times allowing 30 seconds between each brake application.
4. Release the wheel brakes and open each bleeder valve. When oil flows with no air bubbles, close the bleeder valve.
5. Repeat steps 3 and 4.

After bleeding, if the wheel brakes show any signs of dragging or overheating during the first few hours of operation, repeat the entire bleeding procedure.