153 & 163 HYDRAULIC CONTROL – Testing And Adjusting

Hydraulic System

The 5S5123 Hydraulic Testing Group is used to make the pressure test of the hydraulic system. Before any tests are made, visually inspect the complete hydraulic system for leakage of oil and for parts that have damage. For some of the tests, a timer and a measuring rule (either for inches or for millimeters) are usable tools.

To make an adjustment or make a repair to parts in the tank, it is necessary to remove the tank from the machine.

The two and three-valve systems have a series circuit arrangement. The hydraulic pump and the pressure relief valve are common to all circuits. Each circuit has a check valve to help prevent cylinder drift when the valve spool is first moved. The lift circuit also has a make-up valve to add tank oil to the pump flow when the bulldozer blade lowers faster than the pump oil can go to the head ends of the cylinders.

1. The pressure setting of the relief valve can lower the performance of the machine. A too high pressure setting will cause a reduction in the life of hoses and other parts of the system.

2. Lift, tilt, and ripper circuit drift is caused by leakage past cylinder piston seals, control valve seals, check or make-up valves and/or too much spool to valve body clearance.

------ WARNING! ------

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

--------WARNING!------

Visual Checks

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

1. Measure the oil level. Slowly turn the filler cap until it is loose to let the tank pressure lower before the filler cap is removed. Look for air in the oil in the tank.

2. Remove the filter element and look for particles removed from the oil by the filter element. A magnet will separate ferrous particles from nonferrous particles (piston rings, O-ring seals, etc.).

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

Checking Pump Efficiency

For any pump test at a given rpm, the pump flow (gpm) at 100 psi (690 kPa) will be larger than the pump flow (gpm) at 1000 psi (6900kPa).

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.

Test On The Machine

Install a 9S2000 Flow Meter. Run the D6 Tractor engine at 2000 rpm (for D5 Tractor, 1750 rpm). Measure the pump flow at 100 psi (690 kPa) and at 1000 psi (6900 kPa). Use these values in Formula I.

Test on the Bench

If the test bench can be run at 1000 psi and at full pump rpm, find percent of flow loss using Formula I.

If the test bench can not be run at 1000 psi at full pump rpm, run the pump shaft at 1000 rpm. Measure the pump flow at 100 psi (690 kPa) and at 1000 psi (6900 kPa). Use these values in the top part of Formula II. For the bottom part of the formula, run the pump shaft, for D6 Tractor, at 2000 rpm (for D5 Tractor, 1750 rpm). Measure the pump flow at 100 psi.

Operation Checks

Checks of implement operation can be used to help find the source of oil leakage in the hydraulic system. The oil in the hydraulic system must be at an operating temperature of 100° to 120°F (38° to40°C).


Cylinder Drift

The temperature of the hydraulic oil has an effect on the amount of cylinder rod drift. Lift and lower the bulldozer (and the ripper if the tractor has one) many times to increase the temperature of the hydraulic oil in the cylinders and tank. Make a record of the hydraulic oil temperature.

Lift the bulldozer (and the ripper) so it is approximately 10 inches (250 mm) off of the ground. With the control lever in HOLD position (and ripper control in HOLD position), stop the engine. Measure the lengths of the cylinder rods and make a record of each measurement. After 5 minutes measure the lengths of the cylinder rods again. The difference between the first and the last measurement is the cylinder drift.

NOTE: The drift measurements in the chart are for new machines.

If a cylinder rod drift is too much:

1. Check the piston seals in the cylinder (bulldozer cylinder pistons also have plungers to check).

2. Check the condition of the valve stems in the control valves.

3. Check the make-up valve, on the control valve, in the head end circuit for the bulldozer. Cylinder piston seal (and/or plungers for the pistons in the bulldozer cylinders) leakage can be checked.

Lower the bulldozer enough to lift the front of the tractor off of the ground. With the control lever in HOLD position, disconnect the hydraulic line from the rod end of each lift cylinder. After only a few minutes only a very small amount of oil will run out of the rod end opening of the cylinder where the hydraulic line was disconnected. If oil flows out of the opening the seals and/or plungers are the cause of too much cylinder rod drift.

Use the ripper to lift the rear end of the tractor off the ground. With the control lever in HOLD position, disconnect the hydraulic line from the rod end of the ripper cylinder. If oil flows out of the rod end of the cylinder, the piston seal is the cause of too much cylinder rod drift.


Relief Valve

Move the bulldozer up and down. Do this again and again to increase the temperature of the oil in the hydraulic tank. The accuracy of the pressure gauge is better when the temperature of the hydraulic oil is between 100° and 120°F (38° and 49°C).

Move the control lever to FLOAT position and stop the engine.

Remove plug (1) from the elbow on the front of the hydraulic tank. Install a 3P3501 Adapter with a 4M5317 Reducing Bushing in the opening forplug (1). With 4M5317 Reducing Bushing and either 7S8714 Pressure Gauge or 1S8937 Valve and the pressure gauge on one end of 5S4648 Hose Assembly, install the other end of the hose in the reducing bushing in the elbow on the tank.

Hydraulic Tank 1. Plug (in elbow).

Relief Valve Test (Double ValveTank)

Start and run the engine at low idle rpm. The tractor is equipped with either a bulldozer with a hydraulic tilt cylinder or a ripper or both a ripper and a bulldozer with hydraulic tilt. Move either the ripper control lever to RAISE position or the tilt control lever to the TILT LEFT position until either the ripper or bulldozer tilt movement stops.

Run the engine at high idle rpm, look at the test gauge and slowly move the control lever to the same position as before (either ripper RAISE or TILT LEFT). The pressure setting of the relief valve is when the gauge needle does not increase any farther. The correct pressure setting of the relief valve is 2250 ± 25 psi (15 500 ± 170 kPa).


Relief Valve Test (Single Control Valve)

Bulldozer lift cylinders have pistons with plungers and the pump oil pressure can not increase to the pressure setting of the relief valve when the pistons are moved to either the rod ends or head ends of the cylinders.

Move the control lever to the FLOAT position and when the bulldozer is on the ground stop the engine.

Disconnect oil line connection (1) to the head end of the right lift cylinder. Use longer bolts and install a 5H4020 Cover between oil line connection (1). Install a 5H4020 Cover in the oil line connection to the left cylinder head.

Lift Cylinder Oil Lines 1. Oil line connection (for head end of right lift cylinder).

Start and run the engine at high idle rpm. Look at the test gauge and slowly move the control lever toward the RAISE position. The pressure setting of the relief valve is when the gauge needle does not increase any farther. The correct setting of the relief valve is 2250 ± 25 psi (15 500 ± 170 kPa).


Relief ValveAdjustment

The relief valve is part of the control valve in the hydraulic tank. The oil in the tank must be drained and the front cover of the tank removed to get to the location of the relief valve.

A new relief valve has the correct pressure setting. The pressure setting of the relief valve can be adjusted with the relief valve on the Control Valve.

New Relief Valve 1. Locknut. 2. Adjustment screw.

Loosen locknut (1) and turn adjustment screw (2) either clockwise to increase or counterclockwise to decrease the pressure setting of the relief valve. One-half turn of screw (2) changes the pressure setting 155 psi (1070 kPa). Tighten locknut (1) after screw (2) is turned.

Install the cover on the hydraulic tank, connect the oil lines, connect the linkage for the control lever and fill the tank with the correct oil to the level of the gauge on the tank.

If an adjustment was made to the pressure setting of the relief valve, test the changed pressure setting. When the setting of the relief valve is correct, remove the test equipment.



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