773E and 775E Off-Highway Truck Hydraulic System: Hoist and Brake System Troubleshooting

Perform the visual checks before you troubleshoot a problem. Make sure that the transmission is in neutral and stop the engine. During the visual checks, use a magnet to separate ferrous particles (iron and steel) from nonferrous particles (bronze, rubber, and paper).

Check: Check the oil level in the hoist and brake hydraulic tank.

(S/N: BDA1-478) (S/N: BEC1-300)(1) Hoist and brake hydraulic tank

(S/N: BDA479-UP) (S/N: BEC301-UP)(1) Hoist and brake hydraulic tank

(2) Rear brake oil cooler

Check the oil level in hoist and brake hydraulic tank (1). Look for air or water in the sight gauge. Many problems are caused by low oil level or air in the oil. Add oil to hoist and brake hydraulic tank (1), if necessary. See the Operation and Maintenance Manual for the correct type of oil.

Problem: There is an indication of water in the oil.

Probable Cause

• Failure of the rear brake oil cooler (2)

Problem: There is an indication of air in the oil.

Probable Cause

• There is a leak in the oil lines. See "Check for oil leakage".

Problem: The oil level is too low.

Probable Cause

• There is a leak in the oil lines. See "Check for oil leakage". Add oil before you perform any tests.
• Brake cooling oil can leak into the final drive. Check the oil level in each final drive.

Check: Check for oil leakage.

Inspect all oil lines, all hoses and all connections for damage or for leaks. Look for oil on the ground under the machine.

Note: If oil can leak out of a fitting or out of a connection, air can enter the system. Air in the system can be as harmful as having too little oil.

Check: Check the parking brake release hydraulic filter.

(3) Parking brake release hydraulic filter

Remove both elements of parking brake release hydraulic filter (3). Inspect elements for foreign material. Cut the filter open, if necessary.

Note: Parking brake release hydraulic filter (3) has an oil bypass valve. The bypass valve allows the oil to bypass the filter elements whenever the pressure difference between the inlet oil and the outlet oil becomes too high. Any oil that does not flow through the filter element goes directly into the hydraulic circuit. Dirty oil can cause sticking valves and restrictions in valve orifices.

Problem: Rubber particles are found.

Probable Cause

• Seal failure
• Hose failure

Problem: Shiny steel particles are found.

Hoist and brake gear pump(4) Brake pump section

Probable Cause

• Mechanical failure of brake pump section (4) .

Problem: Bronze particles are found.

Probable Cause

• Mechanical failure of the pressure plates in the brake pump section (4) .

Check: Check the screen for the rear brake oil cooler.

(5) Screen

Remove screen (5) for the rear brake oil cooler. Inspect screen (5) .

Problem: Rubber particles are found.

Probable Cause

• Seal failure
• Hose failure

Problem: Shiny steel particles are found.

Hoist and brake gear pump (4) Brake pump section(6) Hoist pump section

(7) Hoist control valve

Probable Cause

• Mechanical failure of the brake pump section (4). See "Check the parking brake release hydraulic filter".
• Mechanical failure of the hoist pump section (6)
• Mechanical failure in the hoist control valve (7)
• Mechanical failure of a hoist cylinder

Problem: Bronze particles are found.

Probable Cause

• Mechanical failure of the pressure plates in the brake pump section (4). See "Check the parking brake release hydraulic filter".
• Mechanical failure of the pressure plates in the hoist pump section (6)

Check: Check the screens inside of the hoist and brake hydraulic tank.

(8) Return screen(9) Suction screen

Drain the oil from the hoist and brake hydraulic tank. Remove the hoses from the back of the hoist and brake hydraulic tank in order to remove return screens (8) and suction screen (9).

NOTICE
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products.Dispose of all fluids according to local regulations and mandates.

Problem: Rubber particles are found.

Probable Cause

• Seal failure
• Hose failure

Problem: Shiny steel particles are found.

Hoist and brake gear pump (4) Brake pump section(6) Hoist pump section

Probable Cause

• Mechanical failure of brake pump section (4). See "Check the parking brake release hydraulic filter".
• Mechanical failure of hoist pump section (6). See "Check the screen for the rear brake oil cooler".

Problem: Bronze particles are found.

Probable Cause

• Mechanical failure of the pressure plates in the brake pump section (4). See "Check the parking brake release hydraulic filter".
• Mechanical failure of the pressure plates in the hoist pump section (6). See "Check the screen for the rear brake oil cooler".

Problem: Black fiber is found.

Probable Cause

• Failure of the rear wheel brakes

Problem: Shiny steel particles and/or chrome particles are found.

Probable Cause

• There is a mechanical failure of a hydraulic cylinder and/or of a cylinder rod. Inspect the cylinder rods for scoring.

Note: If any of the above particles are found during any visual checks, all components of the hydraulic system and of the brake cooling system must be cleaned. Do not use any damaged parts. Damaged parts must be replaced with new parts.

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773E and 775E Off-Highway Truck Hydraulic System: Hoist and Brake System Troubleshooting 2013-01-10T19:06:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown