Usage:
Troubleshooting
PROBLEM 1: Brake pedal rests too low or on the floor.
PROBABLE CAUSE:
1. Brake pedal return spring may be worn out or disconnected.
2. Check brake pedal pivot point for binding.
3. Check for excessive clearance between brake shoes and brake drum. Adjust brakes or replace shoes, if necessary.
4. Check the clearance between the push rod and the master cylinder piston. When brake pedal is at rest, this clearance should be at least .79 mm (.031 in.).
5. Automatic adjusters on service brakes may not be working. Make several forward and reverse brake stops. If pedal does not come up, automatic adjusters may need to be repaired.
6. Check valve in master cylinder could be leaking. Replace the check valve, if necessary.
PROBLEM 2: Brake pedal goes to floor under steady pressure.
PROBABLE CAUSE:
1. Check the brake fluid level in the master cylinder. If low, add clean fluid and bleed the brake system.
2. Poor quality brake fluid. Drain the brake system and refill with approved brake fluid.
3. Air may be trapped in the brake lines. Bleed the brake system to remove air.
4. Check brake lines and components for hydraulic leaks. Repair or replace damaged components.
5. Master cylinder may have damaged components or internal leakage. Repair or replace the master cylinder.
PROBLEM 3: Brake pedal feels soft or spongy when pressed.
PROBABLE CAUSE:
1. Air may be trapped in the brake lines. Bleed the brake system to remove air.
2. Poor quality brake fluid. Drain the brake system and refill with approved brake fluid.
3. Check brake lines and components for hydraulic leaks. Repair or replace damaged components.
4. Brake hoses may be weakened and expanding under pressure. Replace any damaged or defective hoses.
5. Brake shoes may be bent or distorted. Replace brake shoes, if necessary.
6. Check brake drums for cracks or excessive wear. Replace brake drums, if necessary.
PROBLEM 4: Excessive pedal force needed to stop machine.
PROBABLE CAUSE:
1. Brake shoe linings soaked with grease or brake fluid. Correct the source of leakage, and replace brake shoes.
2. Check brake shoe linings for glazing or other damage. Replace brake shoes, if necessary.
3. Check brake drums for cracks or excessive wear. Replace brake drums, if necessary.
4. Master cylinder may have damaged components or internal leakage. Repair or replace the master cylinder.
5. Check brake lines for restrictions. Replace any damaged lines.
PROBLEM 5: Excessive pedal travel needed to apply brakes.
PROBABLE CAUSE:
1. Check for excessive clearance between brake shoes and brake drum. Replace shoes, if necessary.
2. Automatic adjusters on service brakes may not be working. Make several forward and reverse brake stops. If pedal does not come up, automatic adjusters may need to be repaired.
3. Master cylinder may have damaged components or internal leakage. Repair or replace the master cylinder.
PROBLEM 6: Brakes over-react to brake pedal force.
PROBABLE CAUSE:
1. Check for incorrect or distorted brake shoes. Make sure linings are installed tightly on the shoes.
2. Check brake drums for scoring, hard spots, or an out-of-round condition. Refinish or replace damaged brake drums.
3. Make sure brake shoes are centered in the brake drums. Adjust shoe hold down pins, if necessary.
4. Bore of the master cylinder could be rough or corroded. Repair or replace the master cylinder.
PROBLEM 7: Brake pedal pulsates under pressure.
PROBABLE CAUSE:
1. Check brake drums for an out-of-round condition. Refinish or replace damaged brake drums.
2. Check for bent or damaged drive wheel axles. Replace if necessary.
PROBLEM 8: Excessive noise from brakes.
PROBABLE CAUSE:
1. Check for bent, damaged, or incorrect brake shoes. Replace if necessary.
2. Check linings for excessive wear. Brake shoes could be rubbing brake drum.
3. Check brake shoes for foreign material in the linings. Replace brake shoes, if necessary.
4. Check the service brakes for broken return springs or hold down pins. Repair or replace any broken parts.
5. Check brake drums for cracks or scoring. Refinish or replace damaged brake drums.
PROBLEM 9: Brakes do not release properly.
PROBABLE CAUSE:
1. Check brake pedal pivot point for binding.
2. Check the clearance between the push rod and the master cylinder piston. When brake pedal is at rest, this clearance should be at least .79 mm (.031 in.).
3. Service brakes may require adjustment. Automatic adjusters may not be working.
4. Check for bent or distorted brake shoes.
5. Internal parts of the master cylinder may be stuck or damaged. Repair or replace the master cylinder.
6. Check the service brakes for sticking pistons or swollen rubber seals. Repair or replace damaged parts.
7. Check brake lines for restictions preventing return of brake fluid. Replace any damaged brake lines.
Test Procedures
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Sudden movement of the machine or release of fluid under pressure can cause injury to persons on or near the machine. To prevent possible injury, do the procedure that follows before testing and adjusting the brake system. |
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1. Move the machine to a smooth horizontal location. Move away from working machines and personnel.
2. Permit only one operator on the machine. Keep all other personnel either away from the machine or in view of the operator.
3. Engage the parking brake.
4. Stop the engine.
5. Make sure all hydraulic pressure is released before any fitting, hose, or component is loosened, tightened, removed, or adjusted.
When troubleshooting a possible problem in the brake system, perform the Visual Checks first. If a problem is still indicated, perform the other tests and adjustments as necessary to identify and solve the problem.
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To prevent possible personal injury, when tests are made with the machine moving, make sure only one operator is on the machine. Keep other personnel away from the machine. Make sure tests are done in a flat and open area. |
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Reference: Be sure to follow correct safety practices when performing procedures covered in this module. See Safety Page, Form No. SENR7733.
Visual Checks
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Do not check for leaks with your hands. Pin hole (very small) leaks can result in a high velocity fluid stream that will be invisible close to the hose. This fluid can penetrate the skink and cause personal injury. Use cardboard or paper to locate pin holes. |
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A visual check of the brake system and its components is the first step when a diagnosis of a problem is made. Park the machine on level ground and stop the engine. Make the following inspections:
1. Check the level of the fluid in the master cylinder. The fluid level should be approximately 5 mm (.25 in.) from the top edge of the master cylinder reservoir. The fluid should appear clean.
2. If the fluid appears clean but the level is low, add clean fluid as instructed in the Operation and Maintenance Guide for the machine.
3. If the brake fluid is dirty or contaminated, the following steps should be done:
a. Drain the brake fluid from the system.
b. Replace all cups and seals in the master cylinder and service brakes.
c. Flush the brake system with clean brake fluid or alcohol.
d. Fill the system with clean brake fluid.
4. Check for signs of fluid leakage on brake components, and on the ground under the machine.
Service Brake Operation Checks
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These checks involve driving the machine in forward and reverse at full speed. Perform these checks on a hard, level surface. Clear area to the front and rear of the machine. |
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1. With the engine off, press the brake pedal firmly. The pedal should go no more than half way to the floor, and the brake should feel firm.
2. Continue holding the brake pedal down for thirty seconds. The pedal must remain firm, and must not sink down to the floor.
3. Start the engine and allow time for the system to warm up.
4. Release the parking brake.
5. Move the transmission shift lever to the Second Gear position.
6. Move the shuttle lever to the right (Forward) position. Slowly push the shuttle lever forward to propel the machine at full speed.
7. Pull the shuttle lever back toward the Neutral position and use the brake pedal to stop the machine.
8. Place the shuttle lever in the Neutral position.
9. Move the shuttle lever to the left (Reverse) position. Slowly pull the shuttle lever back to propel the machine at full speed.
10. Push the shuttle lever back toward the Neutral position and use the brake pedal to stop the machine.
11. Place the shuttle lever in the Neutral position.
12. Shut the engine off.
13. The service brake should stop the machine within 5.4 meters (18 ft.) in second gear. Braking should be quick and smooth.
14. If the service brake does not perform correctly in these checks, or if there is a different problem with the brake, see Troubleshooting to identify and solve the problem.
Bleeding the Service Brake System
Service Brake Bleeding
(1) Service brake. (2) Bleeder screw. (3) Brake line.
1. Check the master cylinder reservoir level. Add brake fluid, if necessary, so the reservoir is full.
2. Attach a hose to bleeder screw (2) on one of the service brakes (1). Place the other end of the hose in a glass jar partially filled with brake fluid, as shown.
3. Have a helper apply steady pressure to the brake pedal, and open bleeder screw (2).
4. As the brake pedal is pushed to the floor, air bubbles should flow out of the submerged end of the hose.
5. When the brake pedal is down to the floor, close the bleeder screw. Have the helper release the brake pedal slowly.
6. Recheck the brake fluid level in the master cylinder. Add clean fluid, if necessary.
7. Repeat steps 3 through 6 until the fluid coming from the submerged end of the hose is clear and free from bubbles.
8. Close bleeder screw (2) and remove the hose.
9. Repeat steps 1 through 8 for the three other service brakes on the machine.
Parking Brake Operation Check
Parking Brake
(1) Band. (2) Drum. (3) Linkage. (4) Lever. (5) Adjusting knob. (6) Nut. (7) Nut. (8) Springs.
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This test involves running the engine with the transmission engaged and the parking brake applied. Perform this test on a hard, level surface. Clear area to the front and rear of machine. Be prepared for possible movement of the machine. |
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1. Start engine and run at idle speed.
2. Move the transmission shift lever to the Fourth Gear position.
3. Pull parking brake lever (4) back and upward to apply the brake.
4. Move the shuttle lever to the right (Forward) position. Slowly push the shuttle lever forward to increase engine speed.
5. The engine should stall noticeably, and the machine should hold its position.
6. Move the shuttle lever back to the Neutral position.
7. Shut the engine off.
8. If the parking brake does not operate correctly, check the system as follows.
9. Check linkage (3) from lever (4) to band (1). Repair or replace any broken parts or connections.
10. Examine the lining material on the inside of band (1). If any part of the lining has completely worn away, or if the band is damaged, band (1) must be replaced.
11. If band (1) appears all right, but brake does not hold machine, tighten adjusting knob (5) to adjust the brake. Set the adjusting knob so that it takes approximately 27 kg (60 lbs.) of force to lock the brake lever.
12. If adjusting knob (5) does not adjust the brake correctly, do the following steps to adjust band (1).
a. Loosen nut (6).
b. Tighten nut (7). This will compress springs (8) and decrease the diameter of band (1).
c. With brake released, there should be a small gap between drum (2) and band (1). The gap must be just enough to prevent the parking brake from dragging when released.
d. Retighten nut (6).