950 GC Wheel Loader Braking and Hydraulic Fan System Caterpillar

Control Manifold (Charging Valve for the Brake Accumulators) - Test and Adjust

Usage:

Show/hide table

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.

Show/hide table

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.

Show/hide table

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

Required Tools

Show/hide table

Table 1
Required Tools
Part Number	Description
1U-5481	Pressure Gauge Group
8T-0860	Pressure Gauge (0 TO 40,000-KPA (0 TO 5,800-PSI))

Specifications

Show/hide table

Table 2
950 GC Brake Accumulator Charging Valve Pressure
Date	Equipment ID Code
Pump Pressure	Setting	Actual
Cut-In Pressure	11720 ± 340 kPa (1700 ± 50 psi)
Cut-Out Pressure	14490 ± 340 kPa (2102 ± 50 psi)

Introduction

This information includes the following test and adjust:

Control Manifold (Charging Valve for the Brake Accumulators)

Test Preparation

Refer to Testing and Adjusting, "Brake Accumulator - Test and Charge".

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

Show/hide table




Illustration 1	g03731188
Steering Frame in the locked position

Move steering frame lock to the LOCKED position.
Stop the engine. Engage the parking brake.
Depress the brake pedal repeatedly until there is no brake oil pressure.

Test Procedure

Show/hide table




Illustration 2	g03520258
Location of brake accumulator charge valve (Control Manifold) (parts removed for clarity). Right Side view of machine. Behind right rear tire.

Show/hide table




Illustration 3	g03519937
Location of brake accumulator pressure tap (parts removed for clarity). (1) Brake accumulator pressure tap. (2) Locknut on adjustment screw. (3) Adjustment screw.

Connect a 0 to 40000 kPa (0 to 5800 psi) pressure gauge to the brake accumulator pressure tap (1) in the service center. The service center is located in front of the ladder on the right side of the machine.
Start the engine and immediately raise to high idle.
The oil pressure must increase to a maximum. Record this pressure. The resulting pressure is the cutout pressure of the brake accumulator charging valve. The correct cutout pressure should be 14490 ± 340 kPa (2102 ± 50 psi).
With the engine in operation, slowly apply the service brakes. Apply the service brakes several times in succession. Verify that the pressure drops consistently. At the point of the specified cut-in, the pressure begins to increase quickly. The correct cut-in pressure should be 11720 ± 340 kPa (1700 ± 50 psi).

Adjust

After testing, if the cut-in pressure and cutout pressures are not within the specification, stop the engine.
Completely release all the oil pressure from the brake circuit by depressing the brake pedal.
Loosen the hydraulic tank filler cap in order to make sure that there is no residual pressure in the hydraulic oil tank.
Loosen the locknut on the adjustment screw (2).
Note: The charging limits will move together. The range between cut-in pressure and the cutout pressure is not adjustable.
Turn the adjustment screw (3) by a quarter turn. Turning the adjustment screw clockwise will increase the cut-in pressure and the cutout pressure. Turning the adjustment screw counterclockwise will decrease the cut-in pressure and the cutout pressure.
Tighten the locknut on the adjustment screw (2).
Tighten the hydraulic tank filler cap.
Start the engine. Make sure that the cut-in pressure and the cutout pressure are within the specification. If the pressures are not within the specification, repeat Steps 1 through 8.
If the cut-in pressure and the cutout pressure are unable to get within specification, the control manifold should be repaired or replaced.