416, 426 & 436 BACKHOE LOADERS HYDRAULICS Caterpillar


Implement Hydraulic System Testing And Adjusting

Usage:

Introduction

Reference: For Specifications with illustrations, make reference to the Specifications For Backhoe Loaders, Form No. SENR3194. If the Specifications given in Form SENR3194 are not the same as given 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.

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

Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury, do the procedure that follows before testing and adjusting the hydraulic system.

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

1. Move the machine to a smooth horizontal location. Move away from working machines and personnel and lower the buckets or implements (loader and backhoe) and stabilizers to the ground.

2. Permit only one operator on the machine. Keep all other personnel either away from the machine or in view of the operator.

3. Activate the parking brake.

4. Stop the engine.

5. Move the hydraulic control levers to all positions to release the pressure in the hydraulic system.

6. Carefully loosen the filler cap on the hydraulic tank to release the pressure in the tank.

7. Make sure all hydraulic pressure is released before any fitting, hose or component is loosened, tightened, removed or adjusted.

8. Tighten the filler cap on the hydraulic tank.

9. The pressure in the system has now been released and lines or components can be removed.

Procedure

When defining a hydraulic system problem, the following procedure should be followed. First, do Visual Checks. If when complete the problem has not been identified, do Operational Checks. If the problem is still not fully understood, do Instrument Tests. This procedure will help identify hydraulic system problems. As soon as the problem is defined, go to Troubleshooting. The Troubleshooting section will list the probable causes of a known problem. Since there may be more than one cause for a problem, the Troubleshooting section may suggest specific inspections or instrument tests be done. These inspections and tests will help identify which of the causes is most probable.

During a diagnosis of the hydraulic system, remember that correct oil flow and pressure are necessary for correct operation. Oil pressure is caused by resistance to the flow of oil.

Visual Checks

A visual inspection of the hydraulic system and its components is the first step when identifying a problem. Stop the engine, lower the implements and stabilizers to the ground. To remove the tank filler cap, slowly turn the filler cap until it is loose. If oil comes out, let the tank pressure lower before the filler cap is removed. Make the following inspections:

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

Do not check for leaks with your hands. Pin hole (very small) leaks can result in a high velocity oil stream that will be invisible close to the hose. This oil can penetrate the skin and cause personal injury. Use cardboard or paper to locate pin hole leaks.

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

1. Check all backhoe, stabilizer and loader oil line connections for damage and leaks.

2. Follow all backhoe, stabilizer and loader oil lines from the implement connections to valve connections. Check the lines and connections for damage and leaks.

3. Check the control valves for leaks. Look around the relief valves and the primary and secondary resolvers.

4. Check the pump and connections for damage and leaks.

5. Follow the pump lines to the tank and valves. Check the lines for damage and leaks.

6. Check the oil cooler (optional equipment on the 416) and tank for damage and leaks.

7. Check tank oil level.

8. Use a clear bottle or container to get an oil sample from the tank immediately after the machine is stopped. Check for air bubbles in the oil sample.

9. Remove the filter elements and check for particles removed from the oil by the filter elements. A magnet will separate ferrous particles from nonferrous particles (piston rings, O-rings, seals, etc.).

Operation Checks

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

Make reference to WARNING on the first page of the TESTING AND ADJUSTING section.

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

The operation checks can be used to find leakage in the system. They can be used to find a bad valve or pump. The speed of rod movement when the cylinders operate can be used to check the condition of the cylinders and the pump.

Lift, lower, dump and tilt back the loader bucket several times.

Operate each backhoe implement function several times.

Lower and raise the stabilizer several times.

1. Watch the cylinders as they are extended and retracted. Movement must be smooth and regular.

2. Listen for noise from the pump.

3. Listen for the sound of the relief valves. They must not open except when the cylinders are fully extended or retracted, when the bucket is empty.

4. Watch the operation of the return to dig features.

The loader lift control lever has a detent in the FLOAT position.

The loader bucket tilt control lever has a detent in the TILT BACK position (only when the bucket is between full dump and the bucket angle to dig).

Implement and Stabilizer Cylinder Drift Check 416, 426, and 436

The drift rates will change with different conditions of the hydraulic components as well as with the operation, the type of bucket (empty or loaded), hydraulic oil temperature, etc.

The values shown are for an empty bucket. Before measuring drift on the implements, the cylinders must be extended at least five times. Check the oil temperature.

To check the loader lift circuit, lift the bucket to maximum height and move the lift control lever to the HOLD position. Measure the distance (and check the time) that the lift cylinders retract. Compare to the chart.

To check the loader tilt circuit, disconnect the bucket leveller. Lift the bucket to maximum height. Tilt the bucket until it is level. Move the control lever to HOLD. Measure the distance (and check the time) that the tilt cylinder retracts. Compare to the chart.

To check the backhoe boom, bucket and stick cylinders, position implements in the following manner. Raise the boom until it is 45° from the ground. Stick out until the stick is horizontal (parallel to ground). Position the bucket so the bottom (cutting edge) is perpendicular to the ground. If the machine has a factory installed extendable stick, it should be fully retracted. When correctly positioned, move implement control levels to HOLD. Measure the distance (and check the time).

To check stabilizer cylinder drift, put the backhoe in the travel position. Lower the stabilizer and lift the rear wheels about 150 mm (6 in.) off the ground.

If the cylinder drift is too much:

1. Check the makeup valves in the affected control valves.

2. Check the condition of the valve spools in the affected control valves.

3. Check the piston seals in the cylinders.

416 Cylinder Speed Check

Start and run the engine at high idle rpm. Increase oil temperature by operating each of the implements several times. During actual tests, leave the engine in high idle. The following tests should be run through full cylinder stroke.

Earlier (With 4T5601 Bucket Cylinder and 4T6877, 9T5216 & 9T7063 Stick Cylinders)

Later (With 9T7287 Bucket Cylinder and 9T7291 Stick Cylinder)

The following tests should be run from a ground level implement to the fully raised position.

The following tests should be run from fully raised implement to ground level implement. During the tests, the implement may impact the ground heavily. Care should be taken to protect finished ground surfaces.

For the final two tests, position the boom at 45° from horizontal. Fully extend the stick and move the bucket to the fully loaded (closed or curled) position. If the extendable stick has been factory added, it should be fully retracted. Then move the boom control lever to full boom DOWN. Measure the time until the bucket hits the ground. To measure boom pause time, keep the control lever in boom DOWN position and measure the time from when the bucket hits the ground until the rear of the vehicle begins to raise.

If the travel times are not correct:

1. Check the pump efficiency.

2. Check the setting of the relief valves.

3. Check the makeup valves in the affected control valves.

4. Check the valve spools in the affected control valves.

5. Check the piston seals in the cylinders.

426 Cylinder Speed Check

Start and run the engine at high idle rpm. Increase oil temperature to 49°C (120°F) by operating each of the implements several times. During actual tests, leave the engine in high idle. The following tests should be run through full cylinder stroke.

Earlier (With 4T5601 Bucket Cylinder and 4T6968, 9T5220 & 9T7066 Stick Cylinder)

Later (With 9T7287 Bucket Cylinder and 9T7289 Stick Cylinder)

The following tests should be run from a ground level implement to the fully raised position.

The following tests should run from fully raised implement to ground level implement. During the tests, the implement may impact the ground heavily. Care should be taken to protect finished ground surfaces.

For the final two tests, position the boom at 45° from horizontal. Fully extend the stick and move the bucket to the fully loaded (closed or curled) position. If the extendable stick has been factory added, it should be fully retracted. Then move the boom control lever to full boom DOWN. Measure the time until the bucket hits the ground. To measure boom pause time, keep the control lever in boom DOWN position and measure the time from when the bucket hits the ground until the rear of the vehicle begins to raise.

436 Cylinder Speed Check

Start and run the engine at high idle rpm. Increase oil temperature to 49°C (120°F) by operating each of the implements several times. During actual tests, leave the engine in high idle. The following tests should be run through full cylinder stroke.

The following tests should be run from a ground level implement to the fully raised position.

The following tests should run from fully raised implement to ground level implement. During the tests, the implement may impact the ground heavily. Care should be taken to protect finished ground surfaces.

For the final two tests, position the boom at 45° from horizontal. Fully extend the stick and move the bucket to the fully loaded (closed or curled) position. If the extendable stick has been factory added, it should be fully retracted. Then move the boom control lever to full boom DOWN. Measure the time until the bucket hits the ground. To measure boom pause time, keep the control lever in boom DOWN position and measure the time from when the bucket hits the ground until the rear of the vehicle begins to raise.

Resolver Network Check

A resolver is a check valve. It compares two pressures. The lower of the two pressures is blocked. The higher of the pressures or signals goes to the next component in the resolver network.


Typical Control Valve
(1) Primary resolver. (2) Secondary resolver.

There are two resolvers per implement control valve. Primary resolver (1) compares rod to head cylinder pressures. Secondary resolver (2) compares the highest primary signal in its control valve to the highest primary signal in the next control valve. The secondary resolvers are arranged in series stopping with the pump compensator valve.

The signal network can be easily checked. Start the engine and warm up the oil. Run the engine at high idle rpm for this check. Operate each control lever in the following order:

1. Auxiliary (if equipped).
2. Left stabilizer.
3. Boom.
4. Swing.
5. Backhoe bucket.
6. Stick.
7. Right stabilizer.
8. Extendable stick (if equipped).
9. Loader bucket tilt.
10. Loader lift.
11. Multi-purpose bucket (if equipped).
12. Steering.


Bottom Of Backhoe Valve Group
(1) Primary resolvers (typical).

If only one valve section function either fails to work in one or both directions or works slowly in one or both directions, the primary resolver in that control valve may be bad.


Back Of Backhoe Valve Group
(2) Secondary resolver (typical).

If two or more control valves in series (next to each other) fail to work normally, check the secondary resolvers. To check the secondary resolver in any control valve, operate all the control valves in the proper sequence until the last malfunctioning valve is located. The secondary resolver in the last malfunctioning control valve may be bad.

When any resolver (primary or secondary) is suspected of being bad, do the following check. Stall any control valve that is closer to the pump supply. This should supply stall pressure to the entire system. While at stall, try to operate the previously malfunctioning valve. If the malfunctioning valve now works properly, the resolver in question is bad. If the valve doesn't work properly (pressure still too low or blocked), it is not a resolver problem. If a resolver is bad, remove it. Check the seals and resolver. Clean and replace, or replace with a new resolver.

Instrument Tests

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

Make reference to the WARNING on the first page of TESTING AND ADJUSTING section.

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

Instrument testing on the hydraulic system and its components is the final step when diagnosing a problem. Test results should verify the status of a component. Adjusting procedures are provided where needed.

Location of Pressure Taps


Front Of Tractor (416)
(1) Signal line pressure tap. (2) Pump discharge pressure tap. (7) Pump. (8) Compensator valve.


Front Of Tractor (426)
(1) Signal line pressure tap. (2) Pump discharge pressure tap. (7) Pump. (8) Compensator valve.

Hydraulic Oil Contamination Test

The hydraulic oil in this system is SAE 10W. If the oil becomes dirty, component failure could result. Dirty oil can also contribute to overheating.

Start the engine and run at high engine rpm. Actuate all cylinders through at least ten full strokes (do not use loader float for this procedure). Lower all implements and stabilizers to the ground. Stop the engine. Move all control levers through all positions to release pressure in the hydraulic system. Remove the tank filler cap slowly. If oil or pressure is seen or heard coming out, let the tank pressure lower before the cap is fully removed. Connect a hose assembled to quick disconnect (2) in the pump discharge port. Run the free end of the hose into the tank through the fill tube. Make sure all hydraulic controls are in HOLD. Start the engine and run at low idle.

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

Do not operate hydraulic controls.

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

Draw a 50 mL sample through a tee in the hose assembly. The contaminant level must be equal to or less than the following:

416 Pump Discharge Pressure Tests

Pump discharge pressures are known values and can be tested during two specific conditions. These two conditions are low pressure standby and high pressure stall.

Low Pressure Standby Test Procedure

1. Lower all implements and stabilizers to the ground.

2. Install a 0 to 28 000 kPa (0 to 4000 psi) gauge in pump discharge pressure tap (2).

3. Start the engine and run at high idle rpm.

4. Leave all control levers in HOLD.

5. Do not move the steering wheel.

6. The pressure reading must be about 1720 kPa (250 psi). Low pressure standby pressure is equal to margin pressure 1380 ± 140 kPa (200 ± 20 psi) plus the additional pressure needed to keep the pump swashplate at the angle needed to maintain leakage flow. This is about an additional 345 kPa (50 psi).

7. Adjustments to pump output should not be made based on the results of this test. Instead, if the results are not acceptable, the Margin Pressure Test should be run.

High Pressure Stall Test Procedure

5S5123, 5P5224 or 6V4161 Pressure Gauge Kit.

1. Lower all implements and stabilizers to the ground.

2. Shut off the engine and move the control levers to all positions to release system pressure.

3. Relieve tank pressure.

4. Install a 0 to 28 000 kPa (0 to 4000 psi) gauge in pump discharge pressure tap (2).

5. Start the engine and run at high idle rpm.

6. Move all control levers (one at a time) except boom down in both directions to initiate a stall condition. Do not hold any function in stall for more than 10 seconds. If more time is needed, wait 30 seconds before returning to stall.

7. All pressure readings must be 19 000 ± 350 kPa (2750 ± 50 psi). If the pressure readings are all too low or too high, the pressure spool in the compensator valve needs to be adjusted. See COMPENSATOR VALVE ADJUSTING.

426 And 436 Pump Discharge Pressure Tests

Pump discharge pressures are known values and can be tested during two specific conditions. These two conditions are low pressure standby and high pressure stall.

Low Pressure Standby Test Procedure

1. Lower all implements and stabilizers to the ground.

2. Install a 0 to 28 000 kPa (0 to 4000 psi) gauge in pump discharge pressure tap (2).

3. Start the engine and run at high idle rpm.

4. Leave all control levers in HOLD.

5. Do not move the steering wheel.

6. The pressure reading must be about 2940 kPa (425 psi). Low pressure standby pressure is equal to margin pressure 1700 ± 100 kPa (245 ± 15 psi) plus the additional pressure needed to overcome the weight of the pump swashplate and the forces of the bias piston and spring. This is about an additional 1240 kPa (180 psi).

7. Adjustments to pump output should not be made based on the results of this test. Instead, if the results are not acceptable, the Margin Pressure Test should be run.

High Pressure Stall Test Procedure

5S5123, 5P5224 or 6V4161 Pressure Gauge Kit.

1. Lower all implements and stabilizers to the ground.

2. Shut off the engine and move the control levers to all positions to release system pressure.

3. Relieve tank pressure.

4. Install a 0 to 28 000 kPa (0 to 4000 psi) gauge in pump discharge pressure tap (2).

5. Start the engine and run at high idle rpm.

6. Move all control levers (one at a time) except boom down in both directions to initiate a stall condition. Do not hold any function in stall for more than 10 seconds. If more time is needed, wait 30 seconds before returning to stall.

7. All pressure readings must be 19 000 ± 350 kPa (2750 ± 50 psi). If the pressure readings are all too low or too high, the pressure spool in the compensator valve needs to be adjusted. See Compensator Valve Adjusting.

416 Margin Pressure Test

5S5123, 5P5224 or 6V4161 PressureGauge Kits or1U5796 Pressure Differential Group6V8398 O-ring Seals (2 each)FT-1990 (1-modified 6V8731 Union)

1. Lower all implements and stabilizers to the ground.

2. Shut off the engine and move the control levers to all positions to release system pressure.


Loader Tilt Circuit
(3) Hose. (4) Tube. (5) Hose. (6) Tube.

3. Relieve tank pressure.

4. Connect one 0 to 28 000 kPa (0 to 4000 psi) pressure gauge to pressure tap (1) and one to pressure tap (2).

5. Disconnect hose (3) from tube (4) and hose (5) from tube (6).

6. Install two 6V8398 O-rings into the modified 6V8731 Union (FT1990).

7. Install the modified 6V8731 Union between hose (3) and hose (5).

8. Start the engine and run at low idle rpm. Check for leaks.

9. Warm up the hydraulic oil. Check for leaks.

10. Bring the engine to high idle rpm.

11. Activate the tilt lever.

12. The pressure on pump discharge line [pressure tap (2)] should be 1380 ± 140 kPa (200 ± 20 psi) higher than the pressure tap (1).

NOTE: The gauges used should be recently calibrated. If not, do the test twice. Once as described; then, once after switch gauge locations.

13. If the pressure difference is not correct, the flow spool in the compensator valve needs to be adjusted. See Compensator Valve Adjustments.

426 And 436 Margin Pressure Test

5S5123, 5P5224 or 6V4161 PressureGauge Kits or1U5796 Pressure Differential Group6V8398 O-ring seals (2 each)FT-1990 (1-modified 6V8731 Union)

1. Lower all implements and stabilizers to the ground.

2. Shut off the engine and move the control levers to all positions to release system pressure.

3. Relieve tank pressure.

4. Connect one 0 to 28 000 kPa (0 to 4000 psi) pressure gauge to pressure tap (1) and one to pressure tap (2).

5. Disconnect hose (3) from tube (4) and hose (5) from tube (6).

6. Install two 6V8398 O-rings into the modified 6V8731 Union (FT1990).

7. Install the modified 6V8731 Union between hose (3) and hose (5).

8. Start the engine and run at low idle rpm. Check for leaks.

9. Warm up the hydraulic oil. Check for leaks.

10. Bring the engine to high idle rpm.

11. Activate the tilt lever.

12. The pressure on pump discharge line [pressure tap (2)] should be 2070 ± 350 kPa (300 ± 50 psi) higher than the pressure tap (1).

NOTE: The gauges used should be recently calibrated. If not, do the test twice. Once as described; then, once after switch gauge locations.

13. If the pressure difference is not correct, the flow spool in the compensator valve needs to be adjusted. See Compensator Valve Adjustments.

416 Compensator Valve Adjustments


NOTICE

When the compensator is rebuilt, be sure pressure compensator adjustment is backed out to a low pressure setting before engine is started. Severe pump and system damage could be the result.


Pump compensator valve (8) can be tested by running one of the pump discharge tests. The high pressure stall test will tell if the pressure spool in compensator valve (8) needs adjusted. The margin pressure test will tell if the flow spool in compensator valve (8) needs adjusted.


Compensator Valve
(9) Plug. (10) Adjusting screw. (11) Adjusting plug.

Pressure Compensator Spool Adjustment

Adjustments to the pressure compensation spool can be made on the machine. If the high pressure stall test indicates an adjustment is needed, follow this procedure:

1. Lower all implements and stabilizers to the ground.

2. Shut off the engine and move the control levers to all positions to release system pressure.

3. Remove the lockwire and seal from adjusting plug (11).

4. Turn the adjusting plug clockwise to increase the pressure setting and counterclockwise to decrease the setting.

5. Repeat the high pressure stall test to make sure the pressure setting is 19 000 ± 350 kPa (2750 ± 50 psi).

6. When the pressure is adjusted correctly, replace the seal and lockwire.

Flow Compensator Spool Adjustment

Adjustments to the flow compensator spool can be made on the machine. If the margin pressure test indicates an adjustment is needed, follow this procedure:

1. Lower all implements and stabilizers to the ground.

2. Shut off the engine and move the control levers to all positions to release system pressure.

3. Remove plug (9).

4. Turn adjusting screw (10) clockwise to increase the pressure setting and counterclockwise to decrease the setting.

5. Repeat the margin pressure test to make sure the pressure setting is 1380 ± 140 kPa (200 ± 20 psi).

6. When the pressure is adjusted correctly, make sure the seal is good and in place. Replace plug (9).

426 And 436 Compensator Valve Adjustments


NOTICE

When the compensator is rebuilt, be sure pressure compensator adjustment is backed out to a low pressure setting before engine is started. Severe pump and system damage could be the result.


Pump compensator valve (8) can be tested by running one of the pump discharge tests. The high pressure stall test will tell if the pressure spool in compensator valve (8) needs adjusted. The margin pressure test will tell if the flow spool in compensator valve (8) needs adjusted.


Compensator Valve
(12) Adjusting screw. (13) Adjusting screw.

Pressure Compensator Spool Adjustment

Adjustments to the pressure compensation spool can be made on the machine. If the high pressure stall test indicates an adjustment is needed, follow this procedure:

1. Lower all implements and stabilizers to the ground.

2. Shut off the engine and move the control levers to all positions to release system pressure.

3. Loosen the locknut for adjusting screw (13).

4. Turn adjusting screw (13) clockwise to increase the pressure setting and counterclockwise to decrease the setting.

5. Repeat the high pressure stall test to make sure the pressure setting is 19 000 ± 350 kPa (2750 ± 50 psi).

6. When the pressure is adjusted correctly, tighten the locknut for adjusting screw (13).

Flow Compensator Spool Adjustment

Adjustments to the flow compensator spool can be made on the machine. If the margin pressure test indicates an adjustment is needed, follow this procedure:

1. Lower all implements and stabilizers to the ground.

2. Shut off the engine and move the control levers to all positions to release system pressure.

3. Loosen the locknut for adjusting screw (12).

4. Turn adjusting screw (12) clockwise to increase the pressure setting and counterclockwise to decrease the setting.

5. Repeat the margin pressure test to make sure the pressure setting is 1700 ± 100 kPa (245 ± 15 psi).

6. When the pressure is adjusted correctly, tighten the locknut for adjusting screw (12).

Pump Efficiency Tests

This test is designed to tell if a pump is operating within design parameters. Presently only a bench test is available. This test should be run only if all cylinder cycle times are too slow and the resolver network has checked out good.

For any pump test, the pump flow, measured in U.S. gpm (liter/min) at 100 psi (690 kPa) will be larger than the pump flow at 1000 psi (6900 kPa) at the same rpm

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

Method of finding flow loss:

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

If the percent of flow loss is more than 10%, pump performance is not good enough.


*Numbers in examples are for illustration and are not values for any specific pump or pump condition. See Specifications For 416-426 Backhoe Loader Hydraulic System, Form SENR3194, for pump flow of a new pump at 100 psi and 1000 psi.

Test on the Bench

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

If the test bench cannot 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 at 2000 rpm. Measure the pump flow at 100 rpm.

Relief Valves

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

Make reference to WARNING on first page of HYDRAULIC SYSTEM TESTING AND ADJUSTING section.

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

There is no main line relief valve. The pressure spool of the compensator valve acts as a main line relief. It limits system pressure to 19 000 kPa (2750 psi). This can be checked on the machine without supplemental pump pressure. The boom, head end relief valve, is the only other implement relief that can be checked on the machine without supplemental pump pressure. All other implement relief valves are set above the pump compensator spool setting. These all require supplemental pump pressure to check.

3S6224 Electrical Hydraulic Pump1P2375 Quick Coupler (Male)1P2376 Quick Coupler (Female)8T4238 Adapter6V8632 Connector (1-14THD)6V8639 Connector (13/16-16THD)5B1309 Coupling7J9108 Seal6V8731 Seal1U5216 Manifold


Loader Control Valve Group
(14) Tilt rod end. (15) Lift rod end. (16) Multi-purpose bucket rod end. (17) Tilt head end.

Bench Test

1. Lower all implements and stabilizers to the ground.

2. Shut off the engine and move all the control levers to all positions. This releases system pressure.

3. Relieve hydraulic tank pressure.

4. Remove the relief valve to be tested.

5. Install the relief valve in the 1U5216 Manifold.

6. Connect the manifold to the hydraulic test bench.

7. Slowly increase pressure. Note the pressure the relief valve opens. Make an adjustment if needed.

On Machines Tests

The boom, head end relief valve can be checked on the machine without supplemental pump pressure. Use the procedure that follows:

1. Lower all implements and stabilizer to the ground.

2. Shut off the engine and move all the control levers to all positions. This releases system pressure.

3. Relieve tank pressure.

4. Install a 0 to 28 000 kPa (0 to 4000 psi) gauge in signal line pressure tap (1).

5. Start the engine and run at high idle rpm.

6. Warm up the oil.

7. Move the boom to the transport position and lock it in place.

8. Run the engine at low idle.

9. Move the control lever to the DOWN position to initiate a stall. Do not hold the implement in stall more than 10 seconds. If more time is needed, wait 30 seconds before returning to stall.

10. See the chart for correct pressure settings and tolerances.

All other relief valve tests require a supplemental pump supply.


Backhoe Control Valve Group
(18) Boom head end relief valve. (19) Right swing rod end relief. (20) Bucket head end relief. (21) Stick rod end relief valve. (22) Boom rod end relief valve. (23) Left swing rod end relief. (24) Bucket rod end relief valve. (25) Stick head end relief valve.

Use the following procedure to check all implement relief valves except the boom head end.

The testing location will change for each relief valve circuit. There are two possible fitting sizes used depending on the circuit being tested.

1. Assemble two adapter assemblies similar to the picture below.


Adapter Assemblies
(26) 1P2375 Quick Disconnect (male). (27) 5B1309 Coupling. (28) 8T4238 Adapter. (29) 6V8632 1"-14THD Connector. (30) 6V8639 13/16"-16THD Connector. (31) 1P2376 Quick Disconnect [female (not shown)].

2. Lower all implements and stabilizers to the ground.

3. Shut off the engine and move all control levers to all positions. This releases system pressure.

4. Relieve tank pressure.

5. Break the circuit being tested at the cylinder connection. For example, if the boom head end relief valve is being checked, disconnect the line or tube where it connects to the head end of the cylinder. Some oil may drain from the line when disconnected.

6. Install the right adapter assembly into the hose or tube that goes back to the control valve. Make sure the right O-ring is installed correctly. Do not install adapter into the cylinder.

7. The female end of quick disconnect (31) should be connected to 3S6224 Pump Hose.

8. Connect quick disconnect (31) to quick disconnect (26). This now completes the circuit from the supplemental pump to the control valve.

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

Make reference to the WARNING On the first page of HYDRAULIC SYSTEMS TEST AND ADJUSTING section. When the supplemental pump is turned on and the control valve or spool is worn or the control valve malfunctions, the implement whose circuit is being tested may move.

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

9. Turn 3S6224 Pump on. Check for leaks at the connection.

10. Slowly increase pressure. Note the pressure the relief valve opens. Check this actual pressure to the chart.


NOTICE

Pump 3S6224 only has a two gallon reservoir. Pump damage may result if run with an empty reservoir.


Relief Valve Adjustments

See the subject RELIEF VALVES when testing relief valves.


Typical Makeup And Relief Valve
(32) Cap. (33) Locknut. (34) Adjusting screw.

1. Remove protective cap (32).

2. Loosen locknut (33).

3. Turn adjusting screw (34) clockwise for an increase. Turn adjusting screw (34) counterclockwise for a decrease in the pressure setting of the relief valve.

4. After screw (34) is turned for an adjustment, tighten locknut (33) and re-test the adjustment.

5. Install cap (32) after the adjustments are correct.

Bucket Positioner And Kickout Adjustments



(1) Rod end. (2) Cam plate. (3) Rod end. (4) Bolt. (5) Pointer on cam plate. (6) Pointer on lift arm boss on earlier models. (7) Black film on later models.

1. With the machine on level ground, lower the loader bucket flat on the ground and stop the engine.

2. Adjust rod end (3) until pointer (5) on plate (2) aligns with pointer (6) on the lift arm boss on earlier models or black film (7) on later models.

3. Loosen bolt (4) and position the switch wheel against plate (2) in the area shown. When the switch wheel is completely compressed, the clearance between the switch wheel and plate (2) should be 0.5 to 1.0 mm (.020 to .040 in.).


NOTICE

An incorrect adjustment could damage the switch.


4. Move the switch in a direction parallel with plate (2) and toward the rear until a "click" is heard. Tighten bolt (4) without moving the switch plate.

5. Remove the pin from rod end (3) and rotate plate (2). The switch should "click" slightly before pointer (5) on the plate aligns with pointer (6) or black film (7).

6. Fasten rod end (3) to plate (2) with a pin and clip.

7. Start the engine and rotate the bucket to full rackback position. Raise the lift arms until the bucket starts to rotate to dump. Measure the angle of the bottom of the bucket with a magnetic protractor. The angle of the bucket, when it is starting to dump should be 60 ± 2° from horizontal.

8. If it is necessary to adjust the bucket angle, remove the clip and pin from rod end (1). For approximately each degree of correction necessary, turn rod end (1) one revolution.

9. Fasten rod end (1) to the bellcrank with the pin and clip and repeat Step 7.

10. If the bucket angle is correct, tighten all locknuts.

Troubleshooting

Troubleshooting Problem List

1. The temperature of the oil is too hot.
2. Pump makes unusual noise, the cylinders do not move smoothly.
3. Large amount of air in the oil.
4. Pump pressure too low.
5. Pump pressure too high.
6. Pause before pressure is reached in all circuits.
7. Signal pressure not zero (or tank pressure) when all valves in HOLD and steering not used.
8. Any implement moves with control lever in HOLD position.
9. Line reliefs too noisy.
10. Too much implement drift.
11. Implement droops when going from a partially raised position to a raised position.
12. All cycle times too slow.
13. The backhoe boom, bucket or stick cycle times too slow.
14. There is too long of a pause at ground level before raising vehicle during boom lower cycle time check.
15. The backhoe boom, bucket or stick cycle times too fast.
16. The loader lift, tilt or clam, or the backhoe extendable stick or auxiliary cycle times are too slow.
17. The loader lift, tilt or clam, or the backhoe extendable stick or auxiliary cycle times are too fast.
18. Swing cycle times too slow.
19. Swing cycle times too fast.
20. Stabilizer raise cycle time too fast.
21. Stabilizer lower cycle time too fast.
22. Stabilizer cycle times too slow.
23. Stabilizer will not move.
24. Stabilizers are unstable (jerky) when raising (lowering the machine).
25. Backhoe bucket slows or stops in midstroke.
26. Backhoe bucket hits the load (curl) stop hard.
27. The swing cylinders hit the swing stops hard.

PROBLEM 1: The temperature of the oil is too hot.

PROBABLE CAUSE:

1. The viscosity of the oil is wrong.
2. The pressure compensator spool 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 sytem is too high.
6. Oil aeration.
7. A restriction to the flow of cool air through the oil cooler if equipped.
8. The bypass valve on oil cooler is opened.
9. Outside air temperature is too hot.

PROBLEM 2: Pump makes unusual 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 pump. Oil aeration.
4. The pump has too much wear.

PROBLEM 3: A large amount of air in the oil.

PROBABLE CAUSE:

1. A leak in the oil line between the tank and the pump.
2. Failure to correctly bleed the hydraulic system after assembly, inspection or testing.
3. Relief valve constantly opens and closes.
4. Leakage in and around cylinder seals.

PROBLEM 4: Pump pressure too low.

PROBABLE CAUSE:

1. Flow spool side of compensator valve set wrong (margin pressure low).
2. Flow spool spring broken.
3. Pump not upstroking (swashplate blocked or actuator spring broken).
4. Leak in signal network.
5. Low setting in relief valve.

PROBLEM 5: Pump pressure too high.

PROBABLE CAUSE:

1. Pressure spool side of compensator valve set wrong.
2. Pressure spool in compensator valve not moving (stuck).
3. Pump not destroking (actuator piston stuck or swashplate blocked).

PROBLEM 6: There is a pause before pressure is reached in all circuits.

PROBABLE CAUSE:

1. Air in signal network.

PROBLEM 7: Signal pressure is not zero (or tank pressure) when all valves are in HOLD and steering not used.

PROBABLE CAUSE:

1. All controls not in HOLD.
2. Signal network not vented.

PROBLEM 8: Any implement moves with control lever in HOLD position.

PROBABLE CAUSE:

1. The control valve and valve spool have a large amount of wear.
2. A piston seal in a cylinder has a large amount of wear.
3. A leak in a connection between the control valve and the cylinders.

PROBLEM 9: Line reliefs too noisy.

PROBABLE CAUSE:

1. Affected relief valve set too low.
2. Springs in affected relief valve broken or fatigued.
3. Pressure spool side of compensator valve set too high.

PROBLEM 10: Too much implement drift.

PROBABLE CAUSE:

1. Leakage in and around the seals on the piston in the cylinder(s) affected.
2. Low setting of line relief.
3. Leakage past a line relief valve or makeup valve for the affected circuit.
4. The spool in the main control valve is not correctly centered. This problem can be caused by a broken spring or sticky valve spool.
5. If the drift problem is in the stabilizer cylinders, the cause can be any of those above. In addition, the lock valve in the stabilizer affected may not be seated properly.

PROBLEM 11: Implement droops when going from a partially raised position to a raised position.

PROBABLE CAUSE:

1. Air in signal network.
2. Advanced signal passages in the control valve main spool blocked in the affected circuit.
3. The control valve compensator spool spring(s) may be broken or fatigued.
4. If the droop problem is in the backhoe boom circuit, the problem can be any of the above. In addition, the load check valve could be stuck. On later machines, the stick and bucket load check valve could be stuck.

PROBLEM 12: All implement cycle times too slow.

PROBABLE CAUSE:

1. Blockage or leakage in signal network.
2. Margin pressure setting incorrect.
3. Pump not at full stroke. (Actuator piston stuck or swashplate blocked.)

PROBLEM 13: The backhoe boom, bucket or stick cycle times are too slow.

PROBABLE CAUSE:

1. The control valve main spool is not fully shifted for the affected circuit.
2. Blocked or partially blocked load signal going to pump compensator valve or leakage in the signal network.
3. The affected circuit line relief setting is too low.
4. The affected circuit line relief valve is leaking.
5. Leaking in and around the affected cylinder(s) piston seals.
6. Broken flow control spring.
7. Pump not at full stroke. (Actuator piston stuck or swashplate blocked.)
8. Low pump margin pressure setting.
9. If the backhoe bucket cycle time is too slow it can be any of the above. In addition, the cylinder snubber orifice may be blocked or partially blocked.

PROBLEM 14: There is too long of a pause at ground level before raising vehicle during boom lower cycle time check.

PROBABLE CAUSE:

1. The restrictor spool in the backhoe inlet manifold stays open. (Broken restrictor spool spring or restrictor spool sticking.)

PROBLEM 15: The backhoe boom, bucket or stick cycle times are too fast.

PROBABLE CAUSE:

1. The affected control valve compensator spool not limiting flow and pressure. Springs broken or fatigued.

PROBLEM 16: The loader lift or tilt, clam, or the backhoe extendable stick or auxiliary cycle times are too slow.

PROBABLE CAUSE:

1. The control valve main spool is not fully shifted for the affected circuits.
2. Blocked or partially blocked load signal going to pump compensator valves or leakage in the signal network.
3. The affected circuit line relief setting is too low.
4. The affected circuit line relief valve is leaking.
5. Leaking in and around the affected cylinder(s) piston seals.
6. Broken flow control spring.
7. Pump not at full stroke. (Actuator piston stuck or swashplate blocked.)
8. Low pump margin pressure setting.

PROBLEM 17: The loader lift, tilt, clam, or the backhoe extendable stick or auxiliary cycle times are too fast.

PROBABLE CAUSE:

1. The affected control valve compensator spool not limiting flow and pressure. Springs broken or fatigued.

PROBLEM 18: Swing cycle times too slow.

PROBABLE CAUSE:

1. The control valve main spool is not fully shifted.
2. Blocked or partially blocked load signal going to pump compensator valve or leakage in the signal network.
3. Swing relief valve setting too low.
4. Swing relief valve leaking.
5. Leaking in and around the swing cylinder piston seals.
6. Blocked or partially blocked orifice check valve in the cylinder-to-cylinder crossover lines.
7. Broken flow control spring.
8. Pump not at full stroke. (Actuator piston stuck or swashplate blocked.)
9. Low pump margin pressure setting.

PROBLEM 19: Swing cycle times too fast.

PROBABLE CAUSE:

1. The control valve compensator spool not limiting flow and pressure. Springs broken or fatigued.
2. The orifice check valves in the cylinder-to-cylinder crossover lines are missing or reversed.

PROBLEM 20: Stabilizer RAISE cycle time is too fast.

PROBABLE CAUSE:

1. The cylinder head end orifice check valve is missing or has been reversed.

PROBLEM 21: Stabilizer LOWER cycle time is too fast.

PROBABLE CAUSE:

1. Another circuit is at stall speed.
2. Pump margin pressure setting is too high.

PROBLEM 22: Stabilizer cycle times are too slow.

PROBABLE CAUSE:

1. The control valve main spool is not fully shifted.
2. Blocked or partially blocked load signal going to the pump compensator valve or leakage in the signal network.
3. Leaking in and around the affected cylinder piston seals.
4. Pump is not at full stroke. (Actuator piston stuck or swashplate is blocked.)
5. Low pump margin pressure setting.
6. If the cycle times are too slow in LOWER only, the problem can be any of the above. In addition, the orifice check valves may be installed backwards.

PROBLEM 23: Stabilizers will not raise (lowers machine).

PROBABLE CAUSE:

1. There is a hydraulic lock because the pilot signal passage to the lock valve is blocked. (See Item 22 under STABILIZER VALVES.)

PROBLEM 24: Stabilizers are unstable (jerky) when raising (lowering machine).

PROBABLE CAUSE:

1. The rod end orifice check valves are broken, missing or installed backwards.

PROBLEM 25: Backhoe bucket slows or stops in midstroke.

PROBABLE CAUSE:

1. Broken or missing snap ring on cylinder rod. The snubber piston is not held in place and may now work anywhere in the stroke.

PROBLEM 26: Backhoe bucket hits the load (curl) stop hard.

PROBABLE CAUSE:

1. Broken rod end snubber spring.
2. Missing seal on rod end snubber piston.
3. Badly damaged cylinder piston seal.

PROBLEM 27: The swing cylinders hit the swing stops hard.

PROBABLE CAUSE:

1. Broken head end snubber spring on affected cylinder.

Caterpillar Information System:

416, 426 & 436 BACKHOE LOADERS HYDRAULICS Systems Operation
416, 426 & 436 BACKHOE LOADERS HYDRAULIC SYSTEM Bucket Positioner And Kickout Adjustment Procedure
416, 426 & 436 BACKHOE LOADERS HYDRAULIC SYSTEM Bucket Positioner And Kickout Group
416, 426 & 436 BACKHOE LOADERS HYDRAULIC SYSTEM Backhoe Linkage Control Group
416, 426 & 436 BACKHOE LOADERS HYDRAULIC SYSTEM Loader Linkage Control Group
416, 426 & 436 BACKHOE LOADERS HYDRAULIC SYSTEM Multipurpose Bucket Clamp Cylinder (Optional)
416, 426 & 436 BACKHOE LOADERS HYDRAULIC SYSTEM Extendable Stick Backhoe Bucket Cylinder (Optional)
416, 426 & 436 BACKHOE LOADERS HYDRAULIC SYSTEM Extendable Stick Cylinder (Optional)
416, 426 & 436 BACKHOE LOADERS HYDRAULIC SYSTEM Stick Cylinder
416, 426 & 436 BACKHOE LOADERS HYDRAULIC SYSTEM Backhoe Bucket Cylinder
416, 426 & 436 BACKHOE LOADERS HYDRAULIC SYSTEM Relief Valve For Swing Cylinders
416, 426 & 436 BACKHOE LOADERS HYDRAULIC SYSTEM Swing Cylinders (RH & LH)
416 Backhoe Loader Hydraulic System 416 Backhoe Loader Hydraulic System
416, 426, 428, 436 & 438 BACKHOE LOADERS OPERATOR'S STATION Glossary For Electrical Troubleshooting
416, 426, 428, 436 & 438 BACKHOE LOADERS OPERATOR'S STATION Troubleshooting Methods
416, 426, 428, 436 & 438 BACKHOE LOADERS OPERATOR'S STATION Block Diagram
416, 426, 428, 436 & 438 BACKHOE LOADERS OPERATOR'S STATION Individual Circuit Description - (Simplified Schematics)
416, 426, 428, 436 & 438 BACKHOE LOADERS OPERATOR'S STATION Alternator 7T2876 12 Volt Bosch Number 0120489387
416, 426, 428, 436 & 438 BACKHOE LOADERS OPERATOR'S STATION Starter 6T8832 12 Volt Bosch Number 0001369002
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