966M XE and 972M XE Wheel Loaders Power Train, Steering, Braking, Hydraulic, and Machine Systems Caterpillar

Piston Pump (Steering) Margin Pressure - Test and Adjust

Usage:

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Personal injury or death can result if two persons are not used in the following procedure.

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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.

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NOTICE

Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat^® products. Dispose of all fluids according to local regulations and mandates.

Specifications

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Table 1
966M/972M Steering Pump Pressure
Date	Equipment ID Code
Pump Pressure	Setting	Actual
Margin Pressure (High Idle)	2100 ± 100 kPa (305 ± 15 psi)

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Table 2
966M/972M Torque Specifications
Callout	Torque
Locknut (Margin Pressure)	17 ± 3 N·m (150 ± 27 lb in)

Introduction

This information includes the following test:

Margin Pressure

This information includes the following adjustment procedure:

Adjustment Procedure (Margin Pressure)

Required Tools

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Illustration 1	g01879273
Tooling (D)

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Table 3
Tool	Item	Part Number	Description
D		1U-5796	Pressure Differential Tool Gp
D2	6V-4143	Quick Connect Coupler	4
D3	6V-3965	Fitting	3
D4	6V-4144	Quick Connect Coupler	1
D5	8T-0859	Pressure Gauge (0 to 25,000 kPa (0 to 3,600 psi))	1
D5	8T-0861	Pressure Gauge (0 to 60,000 kPa (0 to 8,700 psi))	1
D6	8C-8431	Tee	1
D7	1U-5793	Oil Filter Pressure Differential Gauge Gp	1
D8	6V-0484	O-Ring Adapter	1

Reference: Refer to Special Instruction, SEHS8979, "Component Identification and Calibration of the 1U5796 Differential Pressure Gauge Group" for more information on using Tooling (D).

Test Preparation

Refer to Testing and Adjusting, "Machine Preparation for Troubleshooting".

Refer to Testing and Adjusting, "System Pressure Release".

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Illustration 2	g03133179

Move steering frame lock to the LOCKED position.
Engage the parking brake. Move the transmission direction selector to the NEUTRAL position.

Test Procedure

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Illustration 3	g02694580
(1) Location of the remote pressure taps (hydraulic service center). Right side of machine.

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Illustration 4	g03132199
Hydraulic service center. Fan brake pilot manifold (2) Pressure tap for the steering pump

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Illustration 5	g03133278
Steering load sense pressure tap is located next to the steering control valve. (3) Steering load sense pressure tap

Install a 0 to 60000 kPa (0 to 8700 psi) pressure gauge (D5) to the high-pressure port (D4) of pressure differential gauge group (D7).
Attach one end of hydraulic line (D1) to pressure tap (2). Pressure tap (2) is located in the hydraulic service center that is on the right side of the machine. Attach the other end of hydraulic line to the open end of the tee (D6) of pressure differential gauge group (D7).
Attach another hydraulic line (D1) to the steering load sense pressure tap (3). Attach the opposite end of hydraulic line (D1) to the low-pressure port (D8) of the pressure differential gauge group (D7).
Note: Position pressure differential gauge group (D7) and hydraulic lines (D1) in order to prevent damage from any machine movement. Position the test equipment in order to allow a second technician to observe and record the pressure readings safely.
Start the engine. Operate the engine at high idle. Continuously stall the RACK BACK function while simultaneously raising the lift arms at full speed. When the lift arms are almost raised, cycle the tilt cylinder almost to the FULL DUMP position. Then move the tilt cylinders to the full RACK BACK position. Continuously stall the RACK BACK function and simultaneously lower the lift arms back to the ground level position. Without stalling the RACK BACK function, cycle the lift function to raise the lift arms fully. Then lower the lift arms in order to allow the pump to operate at low-pressure briefly and circulate oil through the system. Repeat this process in order to increase the temperature of the oil to normal operating temperature.
Raise the bucket until the bucket is slightly off the ground. Run the engine at high idle.
Command steering in one direction. Make sure that you turn the steering wheel at a uniform rate. A second technician should look at pressure gauge (D7).
Record the pressure reading on pressure gauge (D7). The reading that is on pressure gauge (D7) is the margin pressure. Margin pressure is the difference between steering pump pressure and the load sense pressure (3). The margin pressure should be 2100 ± 100 kPa (305 ± 15 psi).
Note: The pressure reading on pressure gauge (D5) is the steering pump pressure.
Adjust the flow compensator valve if the margin pressure is not correct.
Run the machine at low idle. Lower the bucket and any attachment to the ground. Stop the engine.
Relieve the hydraulic pressure. See the reference at the start of this procedure for the correct method.
Remove the hydraulic lines and the pressure gauge from the pressure tap.

Note: If you adjust the flow compensator spool in the steering pump pressure and flow compensator valve, perform this test procedure again.

Adjustment Procedure (Margin Pressure)

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Illustration 6	g03581637
Pressure and flow compensator valve. Located below steering pump on right side view of machine. Parts removed for clarity. (5) Pressure and flow compensator valve (6) Adjustment screw

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Illustration 7	g02697132
(5) Pressure and flow compensator valve. (6) Adjustment screw for the flow compensator (margin pressure). (7) Flow compensator spool. (8) Spring. (9) Locknut.

Remove the cover from adjustment screw (6). Loosen locknut (9). Turn adjustment screw (6) clockwise in order to increase the margin pressure. Turn adjustment screw (6) counterclockwise in order to decrease the margin pressure. One turn of adjustment screw (6) changes margin pressure by approximately 1415 kPa (205 psi).
After you turn adjustment screw (6), tighten locknut (9) to a torque of 17 ± 3 N·m (150 ± 26 lb in).
Replace the cover on adjustment screw (6).