Template Name: OML_2_col Template Date: 1994_04_22
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844/642 Telehandler
HYDRAULICS
HYDRAULIC SCHEMATICS, TROUBLESHOOTING, TESTING & ADJUSTMENT PROCEDURES INTRODUCTION
GENERAL TEST PROCEDURES
This section of the Mustang Telehandler s e r v ice m an u al cover s th e hy d rau lic schematics, troubleshooting, testing and adjustment 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.
A single-section gear pump attached to the rear of the transmission provides hydraulic flow for the boom , brake s, s teer ing and fram e leveli ng operations. The priority flow divider directs flow to the steering control valves and the flow divider. The flow divider houses the SAHR (Spring-Applied, Hydraulic Release) park brake valve and directs flow to the joysticks and the main control valve. The excess flow from the priority flow and flow divider valves is directed back to the hydraulic tank.
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.
The joysticks are located on the RH console. They direct the flow from the flow divider to the main control valve for boom functions and frame leveling. An electrical switch on the 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 flow divider 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 SAHR valve control spool shifts the spool, blocks the flow from the flow divider and directs the park brake hydraulic fluid to the reservoir. The spring pressure inside the park brake applies the brake.
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.
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.
WARMING THE ENGINE: Star t th e e ngine and ru n u ntil the co olant temperature gauge is in the normal operating range. WARMING THE HYDRAULIC OIL: 1. Operate the attachment tilt, boom extend, boom lift and frame leveling 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 and frame leveling functions three to five times in both directions to allow warm oil to enter the circuits.
.PRINTED IN U.S.A.
601-1
913250
