HYDROSTATIC DRIVE SYSTEM TESTING Hand controls - forward and reverse

Pretest instructions:

*Operator in seat

*Seat belt buckled

*Service/Run switch in “RUN” position

*Key switch in the “OFF” position

STEP TEST RESULT PROBABLE CAUSE AND CORRECTION

1 Levers should move freely NO

YES

Check control linkage from levers to the pumps.

System OK 2 Stroke both levers forward or

reverse, the levers should return to neutral position

YES NO

System OK

Check neutralizer system for binding or adjustment.

3 Stroke both levers forward or reverse and release one lever, both levers should stay in direction stroked

YES NO

System OK

Check neutralizer system for binding or adjustment

Hand controls - forward and reverse Pretest instructions:

*Operator in seat

*Seat belt buckled

*Service/Run switch in “RUN” position

*Parking brake disengaged

*Key switch in the “RUN” position

*Engine operating at low idle speed

STEP TEST RESULT PROBABLE CAUSE AND CORRECTION

1 Control levers in neutral, unit should not move

YES NO

System OK

Check and adjust for neutral 2 Stroke both levers forward or

reverse, unit should accelerate smoothly

YES NO

System OK

Check for loose or damaged control linkage, if OK go to next step.

3 Check hydraulic oil level and add as required, if

OK go to next step.

4 Check hydrostatic hoses, tubing, and

connections for leaks, if OK go to next step.

5 Check parking brake for being engaged or

adjustment, if OK go to next step.

6 Check hydrostatic charge pressure, if OK go to

next step.

7 Check forward or reverse relief valve operation

and pressure settings.

8 Control levers in neutral park brake YES Control System OK

Before performing any hydraulic test, operate the skid steer to get the hydraulic oil to operating temperature (about 38°C or 100° F above ambient temperature).

For access to hydrostatic testing, remove any attachment from the loader attaching face plate and support the boom on the lockpins.

1. Raise the boom, extend the boom lockpins, 1, and lower the boom down on the lockpins.

3 2. Stop the engine, turn the ignition key to the run

position, and operate the boom and bucket control pedals to relieve pressure in the cylinders. Turn off the key.

3. Raise and support the skid steer with all four wheels off the ground. Support the front of the loader at 1 to the front of the final drive case and at 2 to the rear of the case.

CAUTION

Failure to securely support the skid steer could result in movement of the loader during testing causing serious injury or damage to the equipment.

4 4. Put the “SERVICE/RUN” switch, 1, in the

“SERVICE” position.

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5. Raise the operator’s seat and latch in the raised position, 1.

CAUTION

Never work under a raised seat unless it is securely latched in the raised position.

6. Check the hydraulic oil level and add, if required, to proper level.

WARNING

Gauges, gauge fittings, and hoses must have operating pressure ratings of at least 25% higher than the highest pressures of the system.

Never adjust or replace the relief valves to get higher pressures than those specified by the equipment manufacturer.

Fluid under pressure can have sufficient force to penetrate the skin, causing serious personal injury. Always protect the skin and eyes from escaping fluid under pressure.

Before disconnecting lines or fittings, be sure to turn off the skid loader engine and relieve all pressure. Before applying pressure to the system, be sure all connections are tight and that lines, pipes, and hoses are not damaged.

If injured by escaping fluid, obtain medical assistance at once. Serious infection or reaction can develop if medical treatment is not administered immediately.

Remove any attachment from the mounting plate before loosening or disconnecting any hydraulic lines.

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7 HYDROSTATIC SYSTEM OIL FLOW

Hydrostatic Pumps and Motors High- Pressure Flow

The hydrostatic pumps are driven by the engine through a flex plate drive coupler.

The rear hydrostatic pump, 1, supplies high-pressure oil through high-high-pressure lines, 2, to the left hydrostatic motor, 3, when the left forward/reverse control lever is stroked in either direction.

The front hydrostatic pump, 4, supplies high-pressure oil through high-high-pressure lines, 5, to the

right hydrostatic motor, 6, when the right forward/reverse control lever is stroked in either direction.

The hydrostatic system is protected by four high-pressure relief valves, two each pump, one for forward and one for reverse. All four high- pressure relief valves are the same and factory set at 238 bar (3500 PSI). Do not try changing the pressure setting of these relief valves. If during testing the relief valves are found to be incorrectly set, replace the complete valve cartridge.

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8 Hydrostatic Pump and Motor Charge Pressure

Oil Flow

During the operation of the hydrostatic pumps and motors, oil from the high-pressure system is used for lubrication of the internal rotating parts of the pumps and motors. The lubrication oil drains into the pump and motor housings.

A charge check valve in the return line after the filter at 1, builds backpressure in the return circuit and forces oil through the charge line, 2, into the hydrostatic pump back plate at 3. This charge oil provides replacement oil in the high-pressure circuits that was used for lubrication purposes.

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9 Hydrostatic Pump and Motor Case Drain Flow

During operation of the hydrostatic pumps and motors, oil from the high-pressure circuit used for lubrication oil drains into the pump and motor housings.

The lubrication oil will fill the housings approximately half full. This oil then becomes cooling oil and will

drain from the pumps and motor housings (cases) through drain lines, 1.

The front hydrostatic pump drains internally to the rear pump at 2. The oil will drain from the rear pump and tees into the drain line from the motors. The case drain oil returns to the hydraulic reservoir, 3.

HYDROSTATIC CHARGE SYSTEM