Troubleshooting
PROBLEM 1: Brake does not hold machine.
PROBABLE CAUSE:
Look for an electrical problem, or a hydraulic problem in the brake valve. These could cause oil to be routed to the brake caliper when the brake should be applied. Worn or damaged components in the brake caliper could also reduce the efficiency of the brake.
1. Check brake pads for excessive wear. Replace if necessary.
2. Springs in brake caliper may be weak or worn out.
3. Perform Brake Pressure Test in this module.
4. Check brake switch for damage. Replace if necessary.
5. Check for shorts in the electrical wiring to the solenoid valves and pressure switch.
PROBLEM 2: Brake will not release.
PROBABLE CAUSE:
This could be caused by damage to the brake caliper, or by an electrical or hydraulic problem preventing oil from being routed to the brake caliper.
1. Perform Brake Pressure Test in this module.
2. Check the two solenoid valves, the pressure switch, and the brake switch for damage. Replace if necessary.
3. Look for shorts in the electrical wiring to the solenoid valves and the pressure switch.
4. Check pump efficiency.
5. Check brake caliper for internal damage. Repair or replace if necessary.
PROBLEM 3: Brake pressure too low.
PROBABLE CAUSE:
Low system pressure is likely caused by leakage in the brake valve, or by insufficient pressure from the steer pump.
1. Perform Pump Efficiency Test in this module.
2. Pressure setting of relief valve, located in brake valve, may be too low.
3. Check solenoid valves, relief valve, and check valve for internal leakage. Replace damaged components.
PROBLEM 4: Brake light stays on or flickers during operation.
PROBABLE CAUSE:
This could be caused by internal leakage in the brake valve or a problem in the accumulator. Otherwise, the pressure switch or brake switch could be damaged.
1. Perform Brake Pressure Test in this module.
2. Examine the check valve, located in brake valve, for damage or leakage.
3. Perform the Pressure Switch Continuity Test in this module.
4. Check the brake switch for damage. Replace if necessary.
PROBLEM 5: Brake caliper pulsates or makes excessive noise (squealing, clicking or scraping) when brake is applied.
PROBABLE CAUSE:
This problem is either caused by worn or damaged components in the brake caliper, or by a problem with the fixed rotor.
1. Perform Pad Clearance Measurement in this module.
2. Brake pads may be bent, damaged, or worn out.
3. Check for foreign material imbedded in brake pads.
4. Check the fixed disc for excessive variation in thickness, and excessive lateral runout.
Test Procedures
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Sudden movement of the machine or release of oil 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 hydraulic system. |
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1. Move the machine to a smooth horizontal location. Move away from working machines and personnel and lower implements to the ground.
2. Permit only one operator on the machine. Keep all other personnel either away from the machine or in view of the operator.
3. Activate the parking brake.
4. Stop the engine.
5. Move the hydraulic control levers to all positions to release the pressure in the hydraulic system.
6. Carefully loosen the filler cap on the hydraulic tank to release the pressure in the tank.
7. Make sure all hydraulic pressure is released before any fitting, hose or component is loosened, tightened, removed or adjusted.
8. Tighten the filler cap on the hydraulic tank.
9. The pressure in the system has now been released and lines or components can be removed.
During a diagnosis of the hydraulic system, remember that correct oil flow and pressure are necessary for correct operation. The output of the pump (oil flow) increase with an increase in engine speed (rpm) and decreases when engine speed (rpm) is decreased. Oil pressure is caused by resistance to the flow of oil.
When troubleshooting a possible problem in the secondary/parking brake system, perform the Visual checks first, then do the Brake Operation Check. If a problem is still indicated, perform the other tests and adjustments as necessary to identify and solve the problem.
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Some of the following tests and adjustments are performed with the machine engine operating. When these tests are done away from the operator's station, two people must be working. One person performs the tests and adjustments, and the other should be at the controls. This will help prevent accidental movement of machine. |
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Do not check for leaks with your hands. Pin hole (very small) leaks can result in a high velocity oil stream that will be invisible close to the hose. This oil can penetrate the skin and cause personal injury. Use cardboard or paper to locate pin hole leaks. |
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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
A visual inspection of the hydraulic system and its components is the first step when a diagnosis of a problem is made. Stop the engine, lower the blade to the ground. To remove the tank filler cap, slowly turn the filler cap until it is loose. If oil comes out the bleed hole, let the tank pressure lower before the filler cap is removed. Make the following inspections:
1. Measure the oil level.
2. Look for air in the oil that is in the tank. Do this immediately after the machine is stopped. Use a clear bottle or container to get a sample of the oil. Look for air bubbles in the oil that is in the bottle.
3. Remove the filer elements and look for particles removed from the oil by the filter element. A magnet will separate ferrous particles from nonferrous particles (piston rings, o-ring seals, etc.).
4. Inspect all oil lines and connections for damage or leaks.
5. Inspect electrical wiring for broken connections or damaged components.
Brake Operation Check
Perform the following steps to learn whether the secondary/parking brake is operating properly. Do this check on a dry, level, compacted surface. Clear area in direction of machine travel.
1. Start engine following proper operating procedures.
2. Set speed range shift switch in LOW position.
3. Push the brake switch button down to apply the brake. Lamp, located in brake switch, should light.
4. Set throttle control lever at approximately half throttle.
5. Nudge the propel lever slightly forward. The engine should stall noticeably (or rear wheels spin) and the machine should hold its position.
6. Move the propel lever back to the center/stop position.
7. Move throttle control lever to full throttle position.
8. Pull the brake switch button up to release the brake. Brake switch lamp should darken.
9. Nudge the propel lever slightly forward. The machine should move forward as soon as the propel lever is moved.
10. Move the propel lever back to the center/stop position. Shut engine OFF. Push brake switch down to apply the brake.
11. If the machine moves forward with the brake applied in step 5, perform Brake Pressure Test in this module.
12. If the brake holds the machine in step 5 but brake switch lamp does not light, the bulb should be replaced.
13. If the machine does not move forward in step 8, the brake is not releasing properly. Perform Brake Pressure Test in this module.
Brake Pressure Test
Test Port Location
(1) Test port X4.
1. Remove cap from test port X4 (1) behind operator's seat. Install a 0 to 21 000 kPa (0 to 3000 psi) pressure gauge with a hose and quick disconnect fitting, to test port X4.
2. Start engine and run at full throttle.
3. Push the brake switch button down to apply the brake. Lamp, located in brake switch, should light.
4. Observe and record pressure gauge reading. Pressure reading should be approximately 1030 kPa (150 psi).
5. Pull the brake switch button up to release the brake. Brake switch lamp should darken.
6. Observe and record pressure gauge reading. Pressure reading should be approximately 10 300 kPa (1500 psi).
7. Move throttle control lever to the low idle position.
8. Observe pressure gauge and brake lamp for one minute. Pressure gauge reading should remain around 10 300 kPa (1500 psi), and brake lamp should not light.
9. Shut engine OFF. Push brake switch button down to apply the brake. Pressure gauge reading should drop to zero.
10. Remove pressure gauge from test port X4 (1). Reinstall cap.
11. If pressure gauge reading in step 4 is higher than 1030 kPa (150 psi), the brake solenoid may not be operating properly. Perform Solenoid Valve Electrical Test in this module.
12. If pressure reading in step 4 is all right but brake will not hold machine, there is probably an internal brake problem. Brake caliper components may need to be repaired or replaced.
13. If pressure reading in step 6 is too low to release the brake, refer to Troubleshooting for probable cause.
14. If the pressure reading in step 6 is all right but brake will not release, there is probably an internal brake problem. Brake caliper components may need to be repaired or replaced.
15. If the pressure reading in step 6 is too high, check the following: Perform Relief Valve Pressure Test in this module. Perform Pressure Switch Continuity Check in this module.
16. If the pressure reading in step 8 drops too much, check for internal leakage in the brake valve. Accumulator may not be operating properly.
17. If the pressure reading in step 9 does not return to zero, the brake solenoid may be damaged. Perform Solenoid Valve Electrical Test in this module.
Pump Efficiency Test
Brake Valve
(1) Pressure port. (2) Hydraulic hose to steer pump. (3) Return port. (4) Hydraulic hose to oil cooler.
1. Disconnect hydraulic hose (2) from pressure port (1). Disconnect hydraulic hose (4) from return port (3). Mark the two hoses for reassembly. Plug the two ports (1) and (3) on brake valve to prevent contaminants from entering.
2. Install inlet line of a flow meter to hydraulic hose (2). Install outlet line of flow meter to hydraulic hose (4).
3. Open the manual load valve (on flow meter) fully.
4. Start engine and run at full throttle.
5. Slowly close the manual load valve (on flow meter) to set system pressure at 5516 kPa (800 psi).
6. Observe flow meter. Record pump output reading.
7. Shut engine OFF. Make sure all hydraulic pressure is removed from the system. Disconnect flow meter.
8. Reinstall hydraulic hose (2) to pressure port (1). Reintall hydraulic hose (4) to return port (3).
9. Pump output in step 6 should be approximately 61 liters/min (16 U.S. gpm). If pump output is less than 53 liters/min (14 U.S. gpm), steer pump components may need to be repaired or replaced.
Solenoid Valve Electrical Test
If moving the brake switch button does not apply and release the brake correctly, check electrical wiring to the two solenoid valves as follows:
Brake Valve
(1) Brake solenoid. (2) Pressure solenoid. (3) Ground screw. (4) Wire to pressure switch. (5) Wire to brake switch. (6) Wire to ground screw. (7) Wire to ground screw.
Instrument Panel
(8) Keyswitch. (9) Ten amp fuse.
1. Check the ten amp fuse (9) on instrument panel. Replace if necessary.
2. Turn keyswitch (8) to the OFF position.
3. Touch the leads of an ohmmeter to wires (5) and (6) to measure the resistance of brake solenoid (1).
4. Touch the leads of the ohmmeter to wires (4) and (7) to measure the resistance of pressure solenoid (2).
5. Electrical resistance in steps 3 and 4 should be eight ohms. If either resistance is incorrect, the coil of brake solenoid (1) or pressure solenoid (2) must be replaced.
6. Make sure wires (6) and (7) are connected to ground screw (3). Secure ground connection if necessary.
7. Attach one lead of a voltmeter to ground screw (3). Attach the other voltmeter lead to wire (4). This is to check voltage at pressure solenoid (2).
8. Start engine and run at full throttle.
9. Push brake switch button down to apply the brake. Voltmeter should read approximately 12 volts.
10. Pull brake switch button up to release the brake. Voltmeter should read zero.
11. Shut engine OFF. Push brake switch button down to apply the brake. Disconnect voltmeter.
12. Attach one lead of the voltmeter to ground screw (3). Attach the other voltmeter lead to wire (5). This is to check voltage at brake solenoid (1).
13. Start engine and run at full throttle.
14. Push brake switch button down to apply the brake. Voltmeter should read zero.
15. Pull brake switch button up to release the brake. Voltmeter should read approximately 12 volts.
16. Shut engine OFF. Push brake switch button down to apply the brake. Disconnect voltmeter.
17. If voltmeter reading in steps 9, 10, 14, and 15 is always zero, check whether 12 volts is available at brake switch.
18. If 12 volts is available at brake switch but not at the two solenoid valves, the brake switch may be damaged or the wiring between the brake switch and the solenoid valves may be faulty.
19. If 12 volts is not available at the brake switch, check wiring from brake switch to the alternator. Repair or replace faulty wiring or components.
20. If voltmeter reading in steps 9 and 15 is correct but brake does not operate correctly, brake solenoid (1) or pressure solenoid (2) may be damaged. Repair or replace as necessary.
21. If voltmeter reading step 9 or 10 is not correct, perform Pressure Switch Continuity Check in this module.
22. If voltmeter reading in step 14 or 15 is not correct, brake switch should be checked and replaced if necessary.
Pressure Switch Continuity Test
Pressure Switch
(1) Terminal. (2) Terminal. (3) Wire to pressure solenoid. (4) Wire to brake switch. (5) Wire to brake switch.
1. Disconnect two wires (3) and (4) from terminal (1). Disconnect wire (5) from terminal (2). Mark the wires for reassembly.
2. Set an ohmmeter on its lowest setting.
3. Attach the ohmmeter leads to terminal (1) and terminal (2) of the pressure switch. Electrical resistance should be almost zero.
4. If resistance is not close to zero, the pressure switch must be replaced.
5. Connect wire (3) to wire (5).
6. Set the ohmmeter on its highest setting.
7. Start engine and run at full throttle.
8. Pull brake switch button up to release the brake. Observe ohmmeter. Electrical resistance should be infinite.
9. Shut engine OFF. Push brake switch button down to apply the brake.
10. Disconnect ohmmeter. Reconnect wires (3) and (4) to terminal (1). Reconnect wire (5) to terminal (2).
11. If electrical resistance in step 8 is not infinite, do System Pressure Test in this module. If pressure is too low, refer to Troubleshooting. If pressure is not too low, pressure switch must be replaced.
Relief Valve Pressure Test
Pressure Switch
(1) Terminal. (2) Terminal. (3) Wire to brake switch.
Test Port Location
(4) Test port X4.
Relief Valve Cartridge
(5) Adjusting screw. (6) Locknut.
1. Disconnect wire (3) from terminal (2) of pressure switch. Mark the wire for reassembly.
2. Connect wire (3) to terminal (1).
3. Remove cap from test port X4 (4) behind operator's seat. Install a 0 to 27 600 kPa (0 to 4000 psi) pressure gauge with a hose and quick disconnect fitting to test port X4.
4. Start engine and run at full throttle.
5. Pull brake switch button up to release the brake. Because the pressure switch was bypassed in step 2, brake lamp will remain lit. Oil entering the brake valve will flow through the relief valve.
6. Observe and record the pressure gauge reading. This indicates the setting of the relief valve cartridge.
7. Shut engine OFF. Push brake switch button down to apply the brake.
8. Pressure gauge reading in step 6 should be approximately 13 100 kPa (1900 psi). If pressure is all right, skip to step 14. If pressure is too high or too low, adjust the relief valve cartridge as follows.
9. Loosen locknut (6) while holding adjusting screw (5) to prevent it from turning.
10. Turn adjusting screw (5) in (clockwise) to increase pressure setting, or out (counterclockwise) to decrease pressure setting. 1/2 turn = about 3240 kPa (470 psi) pressure charge.
11. Tighten locknut (6) while holding adjusting screw (5) to prevent it from turning.
12. Repeat steps 4 through 8 to check the new pressure setting. Repeat adjusting procedure if necessary.
13. If turning the adjusting screw does not change the pressure setting, the relief valve cartridge should be removed and replaced with a new part.
NOTE: If pressure is too low, check the following: Examine solenoid valves for leakage. Do the Pump Efficiency Test in this module to see if the steer pump is all right.
14. Remove pressure gauge from test port X4 (4). Reinstall cap.
15. Disconnect wire (3) from terminal (1) of pressure switch. Reconnect wire (3) to terminal (2).
Check Valve, Relief Valve, and Solenoid Valve Check
Brake Valve
(1) Brake solenoid. (2) Pressure solenoid. (3) Relief valve. (4) Check valve.
1. Remove the questionable valve cartridge from the brake valve body.
2. Inspect for visible contamination. Flush with clean mineral spirits to remove contaminants.
3. After flushing, blow dry with clean, filtered air.
4. Through the nose of the cartridge, manually operate the inner working parts several times. Use a wooden or plastic dowel to avoid damaging seals or finished surfaces of the valve.
5. If the inner working parts do not operate properly, dispose of the cartridge and replace with a new one.
6. Inspect the cartridge seals for damage. Replace if necessary.
7. Install the cartridge into the brake valve body. Tighten the cartridge to 40 to 47 N m (30 to 35 lb. ft.).
Pad Clearance Measurement
Perform the following steps to measure the clearance between the brake pads and the fixed disc when the brake is released.
Secondary/Parking Brake
(1) Fixed disc. (2) Brake caliper.
1. Block the vibratory drum on both sides to prevent the machine from rolling.
2. Start engine and run at full throttle.
3. Pull the brake switch button up to release the brake.
4. Insert a feeler gauge blade between brake caliper (2) and fixed disc (1) to measure the clearance between the fixed disc and the brake pad.
5. Repeat step 4 for the opposite side of fixed disc (1).
6. Shut engine OFF. Push brake switch down to apply the brake. Unblock the vibratory drum.
7. The clearance measured in steps 4 and 5 should be .5 mm (.02 in.). If actual clearance is greater, brake pads may need to be replaced. If actual clearance is less, brake is not releasing completely. Refer to Troubleshooting for probable cause.
Fixed Disc Runout Check
Perform the following steps to measure the wobble (runout) of the fixed disc as the vibratory drum rotates.
Secondary/Parking Brake
(1) Yoke. (2) Fixed disc. (3) Vibratory drum.
1. Block the rear wheels securely to prevent the machine from rolling.
2. Jack the front of the machine up so vibratory drum (3) is raised off the ground. Place jack stands under yoke (1) on both sides. Make sure jacks and jack stands are solidly positioned, and are capable of supporting 4530 kg (10 000 lbs.).
3. Set a dial indicator on yoke (1). Adjust so the stylus of the dial indicator touches the rubbing surface of fixed disc (2) approximately 25 mm (1 in.) from its outer edge.
4. Start engine and run at half throttle.
5. Pull the brake switch button up to release the brake.
6. Set the dial indicator at zero. Slowly rotate the vibratory drum one complete turn while watching the dial indicator reading.
7. Shut engine OFF. Lower the front of the machine to the ground. Unblock rear wheels.
8. The total indicator reading in step 6 should not exceed .76 mm (.030 in.). If the rotor runout is excessive, check the following: Fixed disc may need to be refinished or replaced. Drum support assemblies may be damaged, causing excessive wobble in the vibratory drum.
Fixed Disc Thickness Measurement
1. Visually inspect the fixed disc. If there is heavy rust or pitting, scoring, or ridges in the fixed disc, it should be refinished or replaced.
2. Check for varying thickness in the fixed disc using a micrometer. Measure the thickness of the fixed disc at 12 points, about 30° apart and 25 mm (1 in.) from the outer edge.
3. If the thickness variation exceeds .5 mm (.02 in.), the fixed disc should be refinished or replaced.
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The minimum allowable thickness of the fixed disc is 12.2 mm (.48 in.). If worn or refinished below this thickness, the fixed disc must be replaced. |