416C, 426C, 428C, 436C and 438C Backhoe Loaders Axles, Differential and Brakes Caterpillar

Purge Procedure For Two-Wheel Steer

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Personal injury or death can result if two persons are not used in the following procedure.

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Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing serious injury, and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

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Illustration 1	g00354012
Rear Axle (1) Left air purge screw. (2) Right air purge screw.

1. Fill the brake fluid reservoir with oil. Add oil to the brake reservoir during the purge procedure in order to maintain the proper level. Refer to Operation and Maintenance Manual, SEBU6873, "Recommended Oils" and Operation and Maintenance Manual, SEBU6873, "Refill Capacities".

2. Fasten one end of a transparent tube that is 6.4 mm (.25 inch) in diameter to the left air purge screw (1). Put the other end of the tube into a suitable container for collecting the hydraulic oil.

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Illustration 2	g00354214
Brake Pedals (4) Left brake pedal. (5) Right brake pedal. (6) Lock bar.

3. Unlock the lock bar (6) .

4. Depress the right brake pedal (5) and release the right brake pedal. Depress the left brake pedal (4) and release the left brake pedal. This process is called stroking. Continue this process until pressure in the brake system is obtained.

5. Depress both brake pedals and hold both brake pedals.

6. Loosen the left air purge screw (1). Continue depressing the left brake pedal (4) while you hold the right brake pedal (5). As the hydraulic oil flows through the tube, look for air bubbles in the oil. Before the left brake pedal (4) reaches full travel, tighten the left air purge screw (1) .

7. Repeat steps 4 through 6 until there are no air bubbles for five strokes.

8. Repeat steps 4 through 7.

9. Remove the transparent tube from the left air purge screw (1) .

10. Fasten one end of the transparent tube to the right air purge screw (2). The other end of the tube remains in the suitable container for collecting the hydraulic fluid.

11. Stroke the left brake pedal (4) and stroke the right brake pedal (5). Continue this process until pressure in the brake system is obtained.

12. Depress both brake pedals and hold both brake pedals.

13. Loosen the right air purge screw (2). Continue depressing the right brake pedal (5) while you hold the left brake pedal (4). As the hydraulic oil flows through the tube, look for air bubbles in the oil. Before the right brake pedal (5) reaches full travel, tighten the right air purge screw (2) .

14. Repeat steps 11 through 13 until there are no air bubbles for five strokes.

15. Repeat steps 11 through 14.

16. Remove the tube from the air purge screw.

17. Inspect the brake system for leaks.

18. Fill the brake reservoir with oil.

19. Lock the lock bar (6) .

20. Perform the braking system test. Refer to Operation and Maintenance Manual, SEBU6873, "Braking System - Test".

Note: If the brake pedal is spongy during the first hours of operation, perform this procedure again.

Purge Procedure for All Wheel Steer

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Personal injury or death can result if two persons are not used in the following procedure.

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Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing serious injury, and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

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Illustration 3	g00361313
Front View of the Rear Axle (1) Right air purge screw. (2) Left air purge screw.

1. Fill the hydraulic tank with oil. Add oil to the hydraulic tank during the purge procedure in order to maintain the proper level. Refer to Operation and Maintenance Manual, SEBU6873, "Recommended Oils" and Operation and Maintenance Manual, SEBU6873, "Refill Capacities".

2. Fasten one end of a transparent tube that is 6.4 mm (.25 inch) in diameter to the right air purge screw (1). Put the other end of the tube into a suitable container for collecting the hydraulic oil.

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Illustration 4	g00361412
(3) Brake pedal.

3. Depress the brake pedal (3) and release the brake pedal. This process is called stroking. Continue this process until pressure in the brake system is obtained.

4. Depress the brake pedal and hold the brake pedal.

5. Loosen the right air purge screw (1). Continue depressing the brake pedal (3). As the hydraulic oil flows through the tube, look for air bubbles in the oil. Before the brake pedal (3) reaches full travel, tighten the right air purge screw (1) .

6. Repeat steps 3 through 5 until there are no air bubbles for five strokes.

7. Repeat steps 3 through 6.

8. Fasten one end of the transparent tube to the left air purge screw (2). The other end of the tube remains in the suitable container for collecting the hydraulic fluid.

9. Stroke the brake pedal (3). Continue this process until pressure in the brake system is obtained.

10. Depress the brake pedal and hold the brake pedal.

11. Loosen the left air purge screw (2). Continue depressing the brake pedal (3). As the hydraulic oil flows through the tube, look for air bubbles in the oil. Before the brake pedal (3) reaches full travel, tighten the left air purge screw (2) .

12. Repeat steps 9 through 11 until there are no air bubbles for five strokes.

13. Repeat steps 9 through 12.

14. Remove the tube from the air purge screw.

15. Inspect the brake system for leaks.

16. Fill the hydraulic tank.

17. Perform the braking system test. Refer to Operation and Maintenance Manual, SEBU6873, "Braking System - Test".

Note: If the brake pedal is spongy during the first hours of operation, perform this procedure again.