2001/01/29 Caterpillar

Asphalt Paver:

AP-1055B (S/N: 8BM1-UP; ABB1-UP)

BG-2455C (S/N: 6TN1-UP; ACM1-UP)

Reference: Disregard this procedure. See the following replacement procedure.

Note: The following procedures must be performed in order. If the procedures are not completed in order, the procedures will not work properly. If necessary, the Purging and Charging the Hydraulic Pressure is the only procedure that may be performed without completing the earlier procedures. The Purging Ports may not be installed on the track tension rams on some old machines. If the machine is not so equipped, refer to Service Magazine, February 1998, "Proper Remote Air Bleed Installation Procedure for Machines Equipped with MTS Track Systems".

Check for the Hydraulic Pressure In the Accumulator

1. Install a 148-1886 Female Coupler to a 8T-0859 Pressure Gauge .

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Illustration 1	g00639450

2. Attach the coupler to purge port (1) that is on the ram.

   Note: Machines that have the older style of track tension cylinder may have both a hose and a port for purging that is attached to the top of the cylinder.

3. Rotate the gauge in order to open the high pressure quick coupler.

4. Read the pressure. The pressure should be 16550 ± 345 kPa (2400 ± 50 psi). If the pressure is low, you need to check the nitrogen pressure of the accumulator.

Releasing the Track Tension Oil Pressure

Note: This supersedes the procedure in Systems Operation/Testing and Adjusting, KENR5019-02.

1. Shut off the engine.

   Note: Use the following parts in order to assemble the purge line.

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   Table 2

   Parts that are needed
   Quantity	Part Number	Part Name
   1270 mm (50 inch)	122-6887	Hose
   1	124-2111	Permanent Coupling
   1	148-1886	High Pressure Female Coupler
   1	4J-5477	O-Ring Seal
   1	8C-6866	Connector

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The track tension circuits contain trapped oil under pressure. The removal of any fittings before releasing the trapped oil pressure can result in personal injury. To prevent possible injury, refer to the Service Manual procedures for releasing track tension trapped oil pressure before removal of any fittings in the track tension circuits.

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Escaping fluid under pressure, even a pinhole 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. Always use a board or cardboard when checking for a leak.

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Illustration 2	g00639450

2. Connect the high pressure female coupler to purge port (1) on the ram.

   Note: Machines that have the older style of track tension cylinder may have both a hose and a port for purging that is attached to the top of the cylinder.

3. While you hold the coupler, rotate the hose in order to open the high pressure quick coupler. Place the other end of the hose in a clean container. Capture the oil. Release hydraulic tension pressure from the system.

4. The ram will move back in the barrel of the cylinder. The track should have slack.

5. Shut off the quick disconnect. This will prevent air from entering the ram.

6. The pressure is now released from the track tension system.

Checking and Charging the Nitrogen Pressure

Note: Before you check the nitrogen pressure, perform the above procedure in order to release the pressure for the track tension.

Note: Refer to the temperature-pressure chart in order to find the correct accumulator precharge pressure that corresponds to the ambient air temperature.

Procedure for the 107-6328 Accumulator

Illustration 3	g00585691

Note: The left track tension manifold is identical to the right track tension manifold. The right track tension manifold is located below the pump compartment and the manifold is mounted on the mainframe. The left track tension manifold is located below the radiator compartment and the manifold is located on the mainframe.

1. Turn the engine start switch to the OFF position.

2. Use the following steps in order to check the nitrogen charge pressure in the accumulator.

   1. Remove the metal plug at the rear of the accumulator.

   2. Install a 1U-5551 Valve Extension to the end of the 107-6328 Accumulator .

   3. Install a 5P-2963 Adapter to the valve extension.

   4. Install a 7S-8712 Pressure Gauge to the adapter in order to check the pressure. The pressure should be 10340 ± 1520 kPa (1500 ± 220 psi).

      Note: Refer to the temperature-pressure chart in order to find the correct accumulator precharge pressure that corresponds to the ambient air temperature.

   5. If the accumulator pressure is low, check the accumulator for leakage at end covers.

   6. If leakage is found, replace the accumulator.

   7. If no leak is found or you have replaced the accumulator, recharge the accumulator with 7S-5437 Nitrogen Charging Group to a pressure of 10340 ± 1520 kPa (1500 ± 220 psi).

      Note: Refer to the temperature-pressure chart in order to find the correct accumulator precharge pressure that corresponds to the ambient air temperature.

   8. Remove the adapter, the gauge and the valve extension. Install the metal plug at the rear of the accumulator.

      Note: When the nitrogen pressure has been checked and serviced properly, you will need to perform the procedure for Purging and Charging the Hydraulic Pressure.

Procedure for the 130-7623 Accumulator

Illustration 4	g00768790

1. Remove the cover over the plug and make sure that the area does not have any paint or grease on the area. Be sure that the side of the gauge for purging is closed.

2. Rotate the plug counterclockwise by 60° with a 1U-7565 Wrench .

   Note: Do not loosen the plug more than 60°. This will cause the pressure to be lost.

3. Connect 9U-6740 Nitrogen Charging Group and 151-8856 Seal (Charging) to 130-7623 Accumulator first by putting the charging group into the plug on the end of the accumulator.

4. Hold the tee while you thread the charging group onto the accumulator in order to ensure that the tee does not turn.

   Note: Make sure that the charging group is tight.

5. Loosen the plug counterclockwise by 1 to 2 turns.

   Note: Do not turn the plug more than two turns.

6. The gauge should read 15170 ± 1515 kPa (2200 ± 220 psi).

   Note: If the accumulator is not at the proper pressure, service the accumulator with 9U-6740 Nitrogen Charging Group and 151-8856 Seal (Charging). Use the instructions in the charging group in order to service the accumulator to a pressure of 15170 ± 1515 kPa (2200 ± 220 psi). Reference the temperature-pressure chart in order to find the correct pressure that corresponds to the ambient air temperature.

7. Hand tighten the plug clockwise with the tee on the assembly. Relieve the pressure on the gauge by turning the purge valve counterclockwise. Remove the charging group from the accumulator. Tighten the plug to a maximum torque of 11.5 N·m (8.5 lb ft).

   Note: When the nitrogen pressure has been checked and serviced properly, you will need to perform the procedure for Purging and Charging the Hydraulic Pressure.

Purging and Charging the Hydraulic Pressure

Illustration 5	g00639453

1. Connect a 8T-0859 Pressure Gauge to test port (5) on the hopper and grade/slope manifold. The manifold is located on the right side of the machine.

2. Start the engine.

3. Adjust the auxiliary pump pressure compensator in order to raise the pressure to 16550 kPa (2400 psi). Refer to KENR5019-02.

4. Shut off the engine.

5. Remove the guard that covers the track tension manifold.

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Illustration 6	g00768989

6. Connect the auxiliary system oil supply hose to the track tension manifold quick disconnect (2) .

7. Open needle valve (1) on the top of the manifold one to two turns.

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Illustration 7	g00639450

8. Connect the purge line to purge port (1) on the ram. Turn the valve on the female coupler to the OPEN position. Place the other end of the hose in a clean container in order to capture the oil while you purge the system. Secure the end of the purge hose. When the engine is started, high pressure oil will be discharging from this hose in the container.

   Note: Machines that have the older style of track tension cylinder may have both a hose and a port for purging that is attached to the top of the cylinder.

9. Remain clear of the track and start the engine. The ram will quickly move the front idler in the forward direction in order to put tension on the track.

10. Allow the oil to be purged from the track tension system. The mixture will appear white and the mixture will have foam. The air that is discharging can be felt passing through the hose.

11. Shut off the purging hose at the female coupler.

12. Air that is trapped in the system should be allowed to consolidate for four or five minutes.

13. Reopen the purge line and watch the discharged stream of oil for air bubbles. You may cycle the purge valve several times until the oil flow appears free of air. This procedure could require purging two to five gallons of oil per track.

14. Shut off the purge hose at the quick disconnect and close needle valve (1) that is on the track tension manifold to the proper torque.

Note: The maximum torque that should be applied to the needle valve is 13.5 N·m (10 lb ft). Torquing the needle valve over the maximum torque may result in breaking the needle valve.

15. If it is necessary to recharge the opposite track and to purge the opposite track, move the purge hose to the other ram. Repeat the above procedure.

16. Reset the auxiliary pump pressure back to 14475 kPa (2100 psi). This is normal operating pressure of the auxiliary system.

17. Shut off the engine. Allow the auxiliary system pressure on the gauge in test port (5) of the hopper and grade/slope manifold to drop to zero. Disconnect the supply hose at the track tension manifolds and replace the dust caps and covers on the quick disconnect fittings.

18. Reinstall the guard that covers the track tension manifold and tighten the cover bolts.