2003/03/31 Correction to Testing and Adjusting , "Pilot System Pressure - Test and Adjust" {5050, 5050} Caterpillar

Track-Type Tractor:

D11R (S/N: AAF1-UP; 7PZ1-UP)

Systems Operation, Testing and Adjusting, RENR7981, "D11R Track-Type Tractor Hydraulic System", "Pilot Sytem Pressure - Test and Adjust". This module is part of Service Manual, RENR2040. The procedure is incorrect. Refer to the text and graphics that follow.

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Hydraulic oil pressure can remain in the hydraulic system on this machine after the engine and pump have been stopped. Serious injury can result if this pressure is not released before any service is done on the hydraulic systems. In order to prevent possible injury, release the hydraulic system pressure before working on any fitting, hose, or hydraulic component. Lower all attachments to the ground before service is started. If the hydraulic system must be serviced, tested, or adjusted with the attachment in the raised position, the attachments and lift cylinders must be supported properly. Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are being made.

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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause 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.

Oil for the pilot system comes from the fan pump and from the resolver network.

The pressure of the pilot oil that is supplied by the fan pump depends on the engine temperature.

Lower the bulldozer and the ripper to the ground when you are performing a pilot system pressure test.

Stop the engine.

Move the bulldozer and the ripper control lever to all of the positions.

Table 1

Tools Needed
Tool	Description
8T-0857	Pressure Gauge
6V-3081	Hose
6V-4144	Coupler Assembly

1. Assemble the pressure gauge, the hose, and the coupler assembly.

2. Remove the floorplate from the machine.

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Illustration 1	g00986517
Electrohydraulic Valve (1) Pressure tap (P3) (2) Adjustment screw (pilot system) (3) Adjustment screw (pressure reducing valve)

3. Connect the coupler assembly with the pressure gauge on pressure tap (1) .

4. Install the floorplate.

5. Perform the following steps in order to adjust the pilot system pressure.

   1. Start and run the engine at maximum speed.

   2. Ensure that the implement lockout switch is in the UNLOCKED position.

   3. The pressure should read 3930 ± 170 kPa (570 ± 25 psi). Actual pressure depends on the engine temperature. A warm engine has a higher fan speed than a cool engine. This causes a higher pilot pressure.

      Note: Use adjustment screw (2) to adjust the pressure setting for the pilot system in the following steps.

   4. Stop the engine.

   5. Turn the adjustment screw inward in order to raise maximum pressure.

   6. Turn the adjustment screw outward in order to lower maximum pressure.

6. Perform the following steps in order to adjust the pressure from the resolver network.

   1. Position the blade and the ripper to full RAISE position.

   2. Stop the engine and monitor HPS pressure (1) .

   3. Move the bulldozer control lever from NEUTRAL position to RAISE position and hold for three seconds. This will drain the pilot pressure in the accumulator.

   4. Release the bulldozer control lever into NEUTRAL position.

   5. Adjust HPS pressure (1) on the pressure reducing valve (3) to 2070 ± 150 kPa (300.2 ± 21.8 psi).

   6. Lower the implements to ground.

7. After the correct pressure adjustment is set and then checked, remove the test equipment from pressure tap (1) .

8. Install the floorplate.

Note: See the Hydraulic Fan Drive System in the testing and adjusting section if the pressure setting of the pressure reducing valve is not correct.