SCHEMATICS, TROUBLESHOOTING, TESTING & ADJUSTMENT PROCEDURES

This section of the Mustang 519 Telehandler service manual covers the hydraulic schematics, troubleshooting, testing and adjustment procedures.

A single-section gear pump attached to the hydrostatic pump provides hydraulic flow for the main control valve. The main control valve directs flow for the steering control valve, joysticks and isolation valve. The hydrostatic pump provides hydraulic flow for the SAHR brake valve. The excess flow from the gear pump is directed back to the hydraulic tank.

The joysticks are located on the RH console. They direct the flow from the main control valve for boom functions.

An electrical switch on t he right side of the dash is connected to a solenoid that operates the SAHR park brake. When the switch is OFF, the SAHR solenoid is activated and flow from the hydrostatic pump is directed to release the park brake. When the switch is ON, the electrical signal to the solenoid is switched off. The spring on the SA HR valve control spool shifts the spool, blocks the flow from the hydrostatic pump and directs the park brake hydraulic fluid to the reservoir. The spring pressure inside the park brake applies the brake.

The steering wheel is connected directly to the Steering Control Valve. When the steering wheel is turned clockwise (right) or counterclockwise (left) the steering control unit directs flow from the priority flow divider to the steering cylinders. The Steering Mode Valve control solenoids are connected to a 3-way switch on the instrument panel. When the switch is in the neutral position, the flow from the priority flow divider is directed to the front steering cylinder. When the switch is in the 4-Wheel Mode or Crab Mode, the Steering Mode Valve directs flow to or from the front cylinder to the rear steering cylinder. The front and rear steering cylinders are in a series hydraulic circuit through the Steering Mode Valve.

General Test Procedures

Warning

NEVER use your hands to search for hydraulic fluid leaks. Instead use a piece of paper or cardboard. Escaping fluid under pressure can be invisible and penetrate the skin, causing serious injury. If any fluid is injected into your skin, see a doctor at once. Injected fluid must be surgically removed by a doctor familiar with this type of injury or gangrene may result.

ALWAYS wear safety glasses when checking for hydraulic fluid leaks. Escaping fluid can cause permanent eyesight damage or loss if safety glasses are not worn.

Warning

Construction equipment can be dangerous if improperly operated or maintained. This machine should be operated and maintained only by trained and experienced people who have read, understood and complied with the Operator’s Manual.

WARMING THE ENGINE:

Start the engine and run until the coolant temperature gauge is in the normal operating range.

WARMING THE HYDRAULIC OIL:

1.Operate the attachment tilt, boom extend and boom lift cylinders at the end of their stroke for 30 seconds.

2.Repeat Step 1 until the hydraulic oil temperature is at 120°F (49°C).

3.Operate boom functions three to five times in both directions to allo w warm oil to enter the circuits.

RELEASE HYDRAULIC OIL PRESSURE:

1.Engage the park brake.

2.Lower equipment to the ground, return the engine to idle for 30 seconds, then shut off the engine.

3.Turn the key switch on. Operate the joystick in each direction. This should ensure there is no residual pressure trapped in the control circuit. Confirm that there is no attachment or unit movement.

Warning

All trapped hydraulic pressure must be released from the system before installing a gauge in any pressure tap. A sudden release of hot oil could cause burns or other serious injury.

Warning

To prevent damage and/or personal injury when using an in-line flowmeter for testing, ALWAYS be sure the load valve on the flowmeter is fully OPEN before starting the engine.

PRESSURE CHECKING GUIDELINES:

1.Use an accurate gauge.

2.Release hydraulic oil pressure before connecting and disconnecting any gauge.

3.Run the engine at 1000 RPM in the specified Mode Select position.

4.As applicable, fully engage the control for the circuit being tested.

5.If adjustment is necessary, obtain each final pressure by bringing the pressure up to the proper setting. Do not bring the pressure to a higher setting and then lower it to the desired setting.

Warning

Relief valves are provided to protect the hydraulic system. Do not increase relief valve pressure settings above specifications or hydraulic system damage may occur.

Template Name: OML_1_col0-00000

Template Date: 1994_04_22

519 Telehandler HYDRAULICS HYDRAULIC

Template Name: OML_1_col0-00000

Template Date: 1994_04_22

519 Telehandler HYDRAULICS

Main Control Valve Pressure Troubleshooting

Test the pressure at the battery tray test port. Bring engine up to speed then engage a hydraulic function on control valve to force hydraulic oil over the main relief valve. Does the pressure gauge read 3350 psi (230 bar)?

YES

Remove the pressure gauge.

YES

NO Adjust the main relief valve on the Main Control Unit. Can 3350 psi, (230 bar) be obtained?

NO

Remove the pressure gauge. Replace the main control relief valve. Does the gauge read 3350 psi (230 bar)?

YES

Remove the pressure gauge.

NO Repair or replace the main control valve.

Template Name: OML_1_col0-00000

Template Date: 1994_04_22

519 Telehandler HYDRAULICS

Park Brake Pilot Pressure Troubleshooting

Test the pressure at the test port G on the hydrostatic pump. Does the pressure gauge read 370 psi (25 bar)?

Test the pressure at port 1 on the SAHR brake valve with the park brake switch off. Does the pressure gauge read 370 psi (25 bar)? cylinder.

Repair or replace the hydrostatic pump.

Repair or replace the park brake

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