236, 246, 252 and 262 Skid Steer Loaders Machine Systems Caterpillar

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Personal injury or death can result from improperly checking for a leak. Always use a board or cardboard when checking for a leak. Escaping air or fluid under pressure, even a pin-hole size leak, can penetrate body tissue causing serious injury, and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury.

Note: Clean all lines and all components with 4C-6796 Mineral Spirits, and install new filters. After the system has been flushed, dispose of the fluid according to local regulations.

Note: During the filling and the flushing procedure, the hydrostatic system must be at maximum output. The hydrostatic system is normally neutralized when the parking brake is applied. Disengage the parking brake for the following procedure.

Filling the Hydrostatic System

There are two procedures for filling the hydrostatic system on the machine. The recommended procedure should be used when all of the tools are available. The second procedure is the alternative procedure. The second procedure should be used if a 4C-9710 Hand Pump is not available.

Recommended Procedure

1. Open the engine access door.

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Illustration 1	g00787970

2. Attach a coupler assembly on the hose from the 4C-9710 Hand Pump to fill port (1) on the oil filter. Pump hydraulic oil into port (1) until one of the following events occurs.
   • three minutes elapse.

   • the hydraulic oil level is at the middle of the sight gauge.

   This will pump hydraulic oil into the piston pump.

   Note: Do not exceed 4000 kPa (580 psi) in order to fill the charge circuit. Seal failure could result.

3. Add hydraulic oil to the hydraulic oil tank if the oil level has not reached the middle of the sight gauge.

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Illustration 2	g00786943

4. If the fan does not turn after 15 seconds, loosen two hose clamps (2) and disconnect hose (3). Fill the hose with hydraulic fluid and reconnect the hose. Tighten the two hose clamps.

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Illustration 3	g00787989
(4) Charge pressure tap

6. Install the 8T-0855 Pressure Gauge to the charge pressure tap (4) with a 1U-5755 Hose.

7. Lower the cab.

8. Sit in the operator's seat. Fasten the seat belt. Lower the armrest.

9. Start the engine and run the engine at low idle.

10. Look at the pressure gauge. The pressure should be 3200 ± 200 kPa (465 ± 30 psi) within 15 seconds after start-up. If the pressure is low, stop the engine immediately. Check the hydraulic oil level in the tank. Determine the cause for low charge oil pressure before restarting the engine.

    Note: If the charge pressure is not reached within 15 seconds, damage to the hydrostatic system will occur. Do not allow the hydrostatic system to operate with incorrect charge system pressures.

Alternate Procedure

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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.

This procedure should be followed if a 4C-9710 Hand Pump is not available.

1. Release the hydraulic system pressure. Refer to Testing and Adjusting, "Hydraulic System Pressure - Release" for the correct procedure.

2. Raise the cab. Refer to the Operation and Maintenance Manual, "Cab Support Operation" for the proper procedure.

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Illustration 4	g00788017

3. Disconnect the hydraulic hose (5) .

4. Add hydraulic oil to the piston pump until the port is full.

5. Connect the hydraulic hose (5) .

6. Add oil to the hydraulic tank if the level is not in the middle of the sight gauge.

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Illustration 5	g00786943

7. Loosen two hose clamps (2) and disconnect hose (3). Fill the hose with hydraulic fluid and reconnect the hose. Tighten the two hose clamps.

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Illustration 6	g00787989

8. Install the 8T-0855 Pressure Gauge to the charge pressure tap (4) with a 1U-5755 Hose .

9. Lower the cab.

10. Sit in the operator's seat. Fasten the seat belt. Lower the armrest.

11. Start the engine and run the engine at low idle.

12. Look at the pressure gauge. The pressure should be 3200 ± 200 kPa (465 ± 30 psi) within 15 seconds after start-up. If the pressure is low, stop the engine immediately. Check the hydraulic oil level in the tank. Determine the cause for low charge oil pressure before you restart the engine.

    Note: If charge pressure is not reached within 15 seconds, damage to the hydrostatic system will occur. Do not allow the hydrostatic system to operate with incorrect charge system pressures.

Flushing The Hydrostatic System

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Hot oil and hot components can cause personal injury. Do not allow hot oil or hot components to contact skin.

Flushing of the entire hydrostatic system should be performed after a failure of a component or the replacement of a component.

Note: If the oil becomes contaminated, premature component failure could result. Contaminated oil can also contribute to overheating.

Use the following procedure to flush the oil in the system.

Flush the Drive Lines

1. Block the machine. Raise the cab. Refer to the Operation and Maintenance Manual, "Cab Support Operation" for the proper procedure.

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Illustration 7	g00788064

2. Disconnect electrical connection (5) for brake solenoid (6) .

3. Lower the cab.

4. Sit in the operator's seat. Fasten the seat belt. Lower the armrest.

5. Start the engine and allow the machine to run for five minutes before beginning the flushing procedure.

6. Run the engine speed at low idle.

7. Depress the parking brake switch in order to activate the hydrostatic system and the hydraulic system.

8. Move the pilot operated hydraulic control ( hydrostatic) to the FORWARD position. Hold the hydraulic control in the FORWARD position for five seconds after you hear the engine lug slightly.

9. Move the hydraulic control to the NEUTRAL position for five seconds.

10. Move the hydraulic control to the REVERSE position. Hold the hydraulic control in the REVERSE position for five seconds. Release the control to the NEUTRAL position.

11. Adjust the engine speed to high idle. Run the machine at high idle for one minute.

12. Repeat Steps 8 through 10.

13. Check the hydraulic oil contamination level. Refer to Testing and Adjusting, "Hydraulic Oil Contamination - Test" for the proper procedure.

14. If the levels are not low enough, a 102-2828 Oil Filter (Cleanup) can be installed in order to reduce the levels of contamination. Flush the system up to four times. If the levels are not low enough after the fourth time, drain the hydraulic oil and change the hydraulic oil filter. Refer to Operation and Maintenance Manual, "Hydraulic System Oil - Change" and the Operation and Maintenance Manual, "Hydraulic System Oil Filter - Replace" for the correct procedures.

15. When the hydrostatic system is within standards, reconnect the electrical connection (9) for the brake solenoid (10) .

16. Lower the cab and bolt down the cab. Refer to Operation and Maintenance Manual, "Cab Support Operation" for the correct procedure.