Testing And Adjusting

Usage:

Introduction

NOTE: For Specifications with illustrations, make reference to STEERING AND BRAKE SYSTEM SPECIFICATIONS FOR 910 WHEEL LOADER, Form No. REG01255. If the Specifications in Form REG01255 are not the same as in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.

Steering And Brake System

The 5S5123 Hydraulic Testing Group is used to make the pressure test of hydraulic system. Before making any tests, visually inspect the complete hydraulic system by looking for leakage of oil and for parts that have damage.

Show/hide table

When testing and adjusting the hydraulic system, move the machine to a smooth horizontal location. Move away from working machines and personnel. There must be only one operator. Keep all other personnel away from the machine or where the operator can see the other personnel.

Visual Checks

A visual inspection of the hydraulic system and its components is the first step when making a diagnosis of a problem. Stop the engine and lower the bucket to the ground. When the oil is cool so any pressure in the tank will be at a minimum, make the following inspections:

1. Measure the oil level. Slowly turn the filler cap until it is loose. If oil comes out the bleed hole when the filler cap is turned, let the tank pressure lower before removing the filler cap. Look for air in the oil in the tank.

2. Check all oil lines and connections for damage or leaks.

Performance Test List

Performance tests of the steering and brake systems can be used for a diagnosis of poor performance and to find the source of oil leakage inside the hydraulic system.

PROBLEM: Pump makes noise, the cylinder rods do not move smoothly and there are air bubbles in the oil.

PROBABLE CAUSE:

1. The viscosity of the oil is wrong.

2. The relief valve opens at low oil pressure.

3. Loose connection of the oil line on the inlet side of the pump.

4. The pump has too much wear.

PROBLEM: The temperature of the oil is too hot.

PROBABLE CAUSE:

1. The viscosity of the oil is wrong.

2. The relief valve opens at low oil pressure.

3. The pump has too much wear.

4. There is a restriction in an oil passage.

5. The load of the system is too high.

PROBLEM: The output of the pump is low.

PROBABLE CAUSE:

1. Low level of the oil in the tank.

2. The viscosity of the oil is wrong.

3. The pump has too much wear.

PROBLEM: The pressure of the oil is low.

PROBABLE CAUSE:

1. The relief valve opens at an oil pressure that is lower than the pressure in the SPECIFICATIONS.

2. The pump has too much wear.

3. The failure of an O-ring seal in the system.

PROBLEM: Too much force needed to turn steering wheel.

PROBABLE CAUSE:

1. The pressure of the oil is low.

2. The output of the pump is low.

3. Dirt in the steering system.

4. Pump has too much wear.

5. Steering control assembly has too much wear.

PROBLEM: Machine does not turn when steering wheel is slowly turned.

PROBABLE CAUSE:

1. Low level of oil in tank.

2. Output of pump is low.

3. Dirt in steering system.

4. Pump has too much wear.

5. Steering control assembly has too much wear.

PROBLEM: Wheel brake does not operate.

PROBABLE CAUSE:

1. No hydraulic fluid in the reservoir of the master cylinder.

2. Damage in the power cylinder or master cylinder.

3. Damage in the caliper at the wheels.

4. Broken oil line to a caliper.

PROBLEM: Wheel brake slips.

PROBABLE CAUSE:

1. Grease or oil on carrier and lining assembly and discs.

2. Not enough hydraulic fluid in the reservoir of the master cylinder.

3. Too much wear on carrier linings.

PROBLEM: Brake application is not smooth.

PROBABLE CAUSE:

1. Air in hydraulic fluid to calipers at the wheels.

2. Wear on brake discs not even.

PROBLEM: Too much force needed to push brake pedals.

PROBABLE CAUSE:

1. Damage to the brake pedals and pedal linkage.

2. Hydraulic pump output too low or with no pressure.

3. Damage in the power brake master cylinder.

PROBLEM: Parking brake does not hold.

PROBABLE CAUSE:

1. Brake needs adjustment.

2. Too much wear on brake linings.

3. Grease or oil on brake drum and lining.

Checking Pump Efficiency

For any pump test at a given rpm, the pump flow (gpm) at 100 psi (7.0 kg/cm²) will be larger than the pump flow (gpm) at 1000 psi (70.3 kg/cm²).

The difference between the pump flow of two operating pressures is the flow loss.

Flow loss when expressed as a percent of flow loss is used as a measure of pump performance.

If the percent of flow loss is more than 10% for test on the machine or 15% for test on the bench, pump performance is not good enough.

^*Numbers in examples are for illustration and are not values for any specific pump or pump condition. See STEERING AND BRAKE SYSTEM SPECIFICATIONS, Form No. REG01255, for pump flow of a new pump at 100 psi and 1000 psi.

Test On The Machine

Install a 9S2000 Flow Meter. Measure pump flow at 100 psi (7.0 kg/cm²) and at 1000 psi (70.3 kg/cm²) with engine at 2000 rpm.

NOTE: See Tee Test Tooling Chart, Form Number REG00910-02.

Test On The Bench

If the test bench can not be run at 1000 psi at a high rpm, do the first part of the test with the pump shaft rotation at 1100 rpm. Measure pump flow at 100 psi (7.0 kg/cm²) and at 1000 psi (70.3 kg/cm²). Then in order to measure the pump flow for the last part of the test, see STEERING AND BRAKE SYSTEM SPECIFICATIONS, Form No. REG01255, for: Pump rpm at 100 psi with the engine at 2000 rpm.

HYDRAULIC SYSTEM SCHEMATIC
1. Cap. 2. Supply tank for the power and master cylinder for the wheel brakes. 3. Oil lines to brake calipers. 4. Oil line from relief valve. 5. Flow control and relief valve. 6. Oil line from pump to flow control and relief valve. 7. Pump section for hydraulic loader system. 8. Oil line to loader control valve sections. 9. Pump section for steering and brake hydraulic systems. 10. Oil line from supply tank.

Relief Valve

The relief valve is in flow control and relief valve (5). The pressure setting of the relief valve can be tested. An adjustment of the valve is needed if the relief pressure setting is not correct.

HYDRAULIC PUMP
7. Pump section for loader hydraulic system. 8. Oil line to loader control valve sections. 9. Pump section for the steering and brake hydraulic systems. 10. Oil line from supply tank.

1. Stop the engine and loosen the filler cap on the hydraulic tank.

2. Remove the plug in tube (6) which is near pump section (7) and install 5S4648 Hose Assembly in the plug opening in the tube. Install 1S8937 Valve and 7S8714 Pressure Gauge (0 to 4000 psi) in the other end of the hose assembly.

3. Start the engine and run it at high idle speed. Turn the machine to the left and then to the right. Turn the machine against the stop either for a right or a left turn. Look at the pressure gauge and turn the steering wheel farther (and hold it it turned). The reading on the gauge is the pressure setting of the relief valve. The correct pressure setting is 2500 ± 25 psi (175.7 ± 1.8 kg/cm²).

4. If the relief valve needs an adjustment remove the floor plates.

FLOW CONTROL VALVE WITH FLOOR PLATES REMOVED
4. Oil line from relief valve. 5. Flow control and relief valve. 6. Oil line from pump.

5. Remove oil line (4) and the fitting in flow control valve (5).

6. Remove relief valve (11), shims 12 and spring (13).

FLOW CONTROL AND RELIEF VALVE
11. Relief valve. 12. Shims. 13. Spring.

7. Add to shims (12) for an increase or remove a shim for a decrease in the pressure setting of the relief valve.

8. Install spring (13), shims (12) and valve (11). Install the fitting over the valve and connect oil line (4).

9. Start the engine and test the adjustment. If the adjustment is not correct make the adjustment again.

Letting Air From The Brakes - (Bleeding the Brakes)

A flexible hose with .25 in. (6.4 mm) inside diameter and approximately 40 in. (1000 mm) long, a container with a capacity of 1 quart (1 liter), a wrench for screw valve (14) and a pressure bleeder for brakes are used to remove the air from lines (3) between the master cylinder and the brakes.

NOTE: If a pressure bleeder for brakes is not used, two persons are needed to remove the air from the brake lines.

SUPPLY TANK FOR BRAKE FLUID
1. Cap. 2. Tank.

1. Stop the engine.

2. Remove cap (1) and install the hose from the pressure bleeder for brakes on tank (2) where the cap was removed.

NOTE: If a pressure bleeder for brakes is not used, remove cap (1) and fill tank (2) with the correct brake fluid for the brakes and install the cap.

3. Install one end of the flexible hose over the end of screw valve (14) and put the other end of the hose in the brake fluid in the 1 quart (1 liter) container which must be 1/2 full of brake fluid.

4. Loosen screw valve (14) and let the brake fluid and air from the screw valve run through the hose into the brake fluid in the container.

NOTE: If the pressure bleeder for brakes is not used, the other person must push on the brake pedal, release it, and again push on the pedal and release it. This will remove the brake fluid and air through valve (14).

5. When no air can be seen coming from the hose, tighten screw valve (14).

BRAKE FOR RIGHT WHEEL
14. Screw valve.

6. Install the flexible hose on the screw valve (14) and remove the air the same as for the first screw valve.

7. Remove the air from the lines and brakes at each wheel with a brake.

Parking Brake (Mechanical)

The location of the parking brake is in the end of the machine with the engine and transmission. The drive shaft to the front wheels (2) is connected to brake drum (4).

PARKING BRAKE
1. Cable to brake control. 2. Drive shaft to front wheels. 3. Lever. 4. Brake drum.