Product Support Program For Relocating Swing Cylinder Line Relief Valves On Certain 416B, 426B, 428B, 436B, And 438B Backhoe Loaders Caterpillar

NOTE: The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.

NOTE: This Program can only be administered after a failure occurs. The decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS5251" as the Part Number and "7755" as the Group Number. Use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.

NOTE: This Revised Service Letter replaces the February 24, 1997 (Revised August 1997) Service Letter. Changes have been made to the Termination Date, Problem Description, Parts Needed and the Rework Procedure has been modified to include the procedure for installing the 1486518 Swing Spool and deburring the spool centering hardware.

NOTE: If the rework was done prior to the August 1997 Revision (SEBE6004-03), the 1330115 Spring in the swing valve should be replaced with a 6E4317 Spring, or reuse the original compensator springs and spool if available.

Termination Date

Problem

Complaints of swing drift on certain Backhoe Loaders may be attributable to the swing cylinder line relief valve. Swing drift occurs while roading the machine or using the loader without the swing pin in place. In addition to problems with the relief valve, there are several additional causes that can contribute to swing drift. It is necessary to perform the trouble shooting section of this Product Support Program to identify these additional root causes for the drift. Once the additional causes have been solved, it is necessary to replace the swing spool and relocate the line relief valve using a block, adapter and lines that will have to be installed on the machine.

Affected Product
Model & Identification Number

Group 1

416B (8SG1-14798 8ZK1-11031 )

426B (5YJ1-2377 6KL1-2448 )

436B (6MJ1-819 7FL1-963 )

Group 2

428B (7EJ1-4253)

438B (3KK1-1613)

Group 3

428B (7EJ4254-8652)

438B (3KK1614-3634)

Parts Needed

Group 1

2 - 6E0358 Ring

2 - 7F8607 Seal

2 - 3K0360 Seal

2 - 4K1388 Seal

2 - 5K9090 Seal

1 - 9S0671 Hose (14")

2 - 8T4121 Washer

2 - 8T4133 Nut

2 - 8T4178 Bolt

5 - 6V8398 Seal

2 - 6V8625 Elbow

1 - 6V8639 Connector

1 - 6V9837 Tee

1 - 6V9965 Coupling Assembly

1 - 6V9967 Coupling Assembly

1 - 7X1447 Coupling

1 - 7X1449 Coupling

1 - 9X2350 Hose (17")

1 - 1394156 Adapter

1 - 1394157 Block

1 - 1486518 Spool

Group 2

2 - 6E0358 Ring

2 - 7F8607 Seal

3 - 7J9108 Seal

2 - 3K0360 Seal

2 - 4K1388 Seal

2 - 5K9090 Seal

1 - 9S0671 Hose (14")

1 - 8T1712 Coupling Assembly

2 - 8T4121 Washer

2 - 8T4133 Nut

2 - 8T4178 Bolt

2 - 6V8398 Seal

2 - 6V8625 Elbow

1 - 6V8639 Connector

1 - 6V9838 Tee

1 - 6V9965 Coupling Assembly

1 - 7X1447 Coupling

1 - 7X1449 Coupling

1 - 9X2350 Hose (17")

1 - 1394156 Adapter

1 - 1394157 Block

1 - 1486518 Spool

Group 3

1 - 3D2824 Seal - O-Ring

2 - 6E0358 Ring

2 - 7F8607 Seal

3 - 7J9108 Seal

3 - 3K0360 Seal - O-Ring

2 - 4K1388 Seal - O-Ring

1 - 5K9090 Seal - O-Ring

1 - 6K8178 Clip

1 - 8T0404 Elbow

2 - 8T4121 Washer

2 - 8T4133 Nut

2 - 8T4178 Bolt

2 - 6V8397 Seal - O-Ring

1 - 6V8398 Seal - O-Ring

1 - 6V8625 Elbow

1 - 6V8723 Elbow

1 - 6V9838 Tee

1 - 6V8634 Connector - Seal

1 - 1226889 Hose (32")

1 - 1226890 Hose (27")

1 - 1242114 Coupling

1 - 1242117 Coupling

1 - 1242144 Coupling

1 - 1242148 Coupling

1 - 1394156 Adapter

1 - 1394157 Block

1 - 1486518 Spool

Action Required

See attached rework procedure.

Service Claim Allowances

Parts Disposition

Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.

Attach.

(1-Rework Procedure)

Rework Procedure

Part 1 - Perform Swing Drift Test

Use the troubleshooting guide (Illustration 1) to diagnose the cause(s) for the swing drift.

Illustration 1

Swing Circuit Drift Test Procedure

1. Position the machine on a level surface with the implements in the service position (boom locked, stick fully in, loader bucket flat on the ground).

2. Allowable drift rates are for 38 degrees C oil temperature. If temperature is lower, heat the system by stalling the boom down line relief valve.

3. Cycle the swing to the left and right and back to center 5 times.

4. Use swing cylinders to position the hoe straight out behind the tractor. Position stick cylinder to full extension. Use the boom cylinder to position the bucket 400 mm to 600 mm above the ground. Use the bucket cylinder to orient the bottom of the bucket parallel to the ground.

5. Measure the hydraulic oil temperature. For temperatures other than 38 degrees C, adjust the drift test time as per Table 1. For intermediate points, adjust drift time by interpolating between adjacent points.

6. With the loader bucket flat on the ground, use the stabilizers to tilt the machine 10 degrees toward the machine right-hand side.

7. Turn the engine off. Measure the drift on the machines left-hand side swing cylinder. The maximum allowable cylinder drift in either direction is 10 mm of extension in 5 minutes (see Table 1).

8. Repeat the drift test with the machine tilted to the left-hand side, measuring drift on the machine right-hand side cylinder.

Swing Cylinder Drift Procedure

1. Position the machine on a level surface with the implements in the service position (boom locked, stick fully in, loader bucket flat on the ground).

2. Allowable drift rates are for 38 degrees C oil temperature. If temperature is lower, heat the system by stalling the boom down line relief valve.

3. Cycle the swing to left and right and back to center 5 times.

4. Use swing cylinders to position the hoe approximately 45 degrees from center. Position stick cylinder to full extension. Place the backhoe bucket on the ground, and disconnect swing cylinder hoses from swing cylinders. Be sure to disconnect lines from valve to cylinder, and not cylinder to cylinder. Plug hoses and cap cylinder ports. Then use boom cylinder to position bucket 400mm to 600mm above the ground. Use the bucket cylinder to orient the bottom of the bucket parallel to the ground.

5. Measure the hydraulic oil temperature. For temperatures other than 38 degrees C, adjust the drift test time as per Table 1. For intermediate points, adjust drift time by interpolating between adjacent points.

6. With the loader bucket flat on the ground, use the stabilizers to tilt the machine 10 degrees toward the machine right-hand side.

7. Turn the engine off. Measure the drift on machine left-hand side swing cylinder. The maximum allowable cylinder drift in either direction is 2 mm of extension in 5 minutes (see Table 1).

8. Repeat the drift test with the machine tilted to the left-hand side, measuring drift to the machine right-hand side cylinder.

In addition to any faults found with the troubleshooting guide, it is necessary to relocate the swing section pilot operated relief valve located on top of the swing section.This rework will require the parts previously described for installation.The routing for this installation is included in rework Part 2.

Rework Part 2 - Installing The Remote Mounted Pilot Relief Valve

For Group 1:

To mount the 1394157 Block, it is necessary to locate the swing line boss. The recommended location is detailed in Illustration 2.

The plumbing for connecting the 1394157 block is shown in Illustration 4.

1. Remove the right swing cylinder line from the swing section.

2. Connect a 6V9837 Tee into the right cylinder line to the swing section. Use 6V8398 O-rings when connecting the Tee.

3. Secure the 1394157 Block to the right frame assembly as shown in Illustration 3.

4. Remove the relief valve from the swing section and relocate it to the remote mounted block as shown in Illustration 3. Tighten to a torque of 70 ± 7 N·m (52 ± 5 ft lb). Install new seals on the relief valve if necessary (5K9090 Seal, 6EO358 Back-Up Ring, and 4K1388 Seal).

5. Install 3K0360 O-rings onto 6V8625 Elbows, then install into remote block.

6. Install seals (5K9090 Seal, 6EO358 Back-Up Ring, and 4K1388 Seal) on the 1394156 Adapter, and install the adapter in the relief valve port in the swing section. Tighten to a torque of 70 ± 7 N·m (52 ± 5 ft lb).

7. Connect an 9X2350 Hose, 43 cm long with 7X1447 and 7X1449 Couplings between the 1394156 Adapter and horizontal port on the 1394157 Block as shown in Illustration 3.

8. Connect an 9S0671 Hose, 34 cm long hose with 6V9965 Couplings and 6V9967 Connectors between the 6V9837 Tee and the vertical port on the 1394157 Block.

NOTE: It is necessary to bleed the air from the system. Perform this task by placing the machine up on the stabilizers, then extend the boom and stick to full extension. Set engine speed to at least 1500 Rpm. Use the swing lever to swing the boom back and forth at least ten times in each direction. This will blow the relief valves and purge the air from the system.

For Group 2:

To mount the 1394157 Block, it is necessary to locate the swing line boss. The recommended location is detailed in Illustration 2.

The plumbing for connecting the 1394157 block is shown in Illustration 10.

1. Remove the right swing cylinder line from the swing section.

2. Connect a 6V9838 Tee into the right cylinder line to the swing section. Use 7J9108 Seals when connecting the Tee.

3. Secure the 1394157 Block to the right frame assembly as shown in Illustration 3.

4. Remove the relief valve from the swing section and relocate it to the remote mounted block as shown in Illustration 3. Tighten to a torque of 70 ± 7 N·m (52 ± 5 ft lb). Install new seals on the relief valve if necessary (5K9090 Seal, 6EO358 Back-Up Ring, and 4K1388 Seal).

5. Install 3K0360 O-rings onto 6V8625 Elbows, then install into remote block.

6. Install seals (5K9090 Seal, 6EO358 Back-Up Ring, and 4K1388 Seal) on the 1394156 Adapter, and install the adapter in the relief valve port in the swing section. Tighten to a torque of 70 ± 7 N·m (52 ± 5 ft lb).

7. Connect an 9X2350 Hose, 43 cm long with 7X1447 and 7X1449 Couplings between the 1394156 Adapter and horizontal port on the 1394157 Block as shown in Illustration 3.

8. Connect an 9S0671 Hose, 34 cm long hose with 6V9965 Couplings and 8T1712 Connectors between the 6V9838 Tee and the vertical port on the 1394157 Block.

NOTE: It is necessary to bleed the air from the system. Perform this task by placing the machine up on the stabilizers, then extend the boom and stick to full extension. Set engine speed to at least 1500 Rpm. Use the swing lever to swing the boom back and forth at least ten times in each direction. This will blow the relief valves and purge the air from the system.

For Group 3:

First move the slide frame to the right hand side of the vehicle to allow access to the backhoe valve. Using the stabilizers lift the machine sufficiently to remove the left hand side rear drive wheel and tire to allow access to mount the valve block. Lower the boom and stick in a position towards the right hand side of the vehicle and on the floor. Shake out all pressure from the backhoe valve circuits.

1. Loosen the bolts of the 1113799 and 1113798 Hose Clamps on both sides. On the right hand side only, remove the top bolt. Disconnect the swing hoses at the backhoe valve (see Illustration 8).

2. Remove swing hose connectors from the backhoe valve. Disconnect the top bucket and boom hoses at the valve and remove the two connectors (left hand and right band side) of the swing section.

3. Fit the 3D2824 O-ring to the large 8T0404 Elbow and the upper section of the backhoe valve with the elbow pointing up. Tighten. Fit the top bucket and boom section connectors and Hoses, adjacent to the swing section.

4. Insert the 7J9108 O-ring in the elbow and fit the 6V9838 Tee with the elbow connection facing the rear (leave loose at this stage). Add the 7J9108 O-ring to the tee piece facing the connection and connect swing hose (leave loose).

5. Add the 6K8178 Clip to the swing hose (Illustration 8) and fit hose with bolt to the top hose clamp (right hand side). Tighten all hose clamps, hose connections, and tee piece on elbow.

Mounting Of Valve Block

1. Mount the valve block by drilling two 11 mm holes in the left hand side of the frame. The top front mounting hole is 155 mm from the bottom of the frame and 240 mm from the inside of the back flange of the frame. (See Illustration 7).

2. Position the block parallel to the bottom of the frame. Mark through and drill the second hole.

Assemble The Valve Block

1. Fit to the 6V8625 Elbow (top), 6V8723 Elbow (bottom),and 3K0360 O-rings at the lock-nut connections. Then install the elbows to the valve block (leave loose).

2. Remove the relief valve from the swing section and relocate it to the remote mounted block as shown in Illustration 3. Tighten to a torque of 70 ± 7 N·m (52 ± 5 ft lb). Install new seals on the relief valve if necessary (5K9090 Seal, 6EO358 Back-Up Ring, and 4K1388 Seal).

3. Fit the assembled valve block to the holes in the frame and mount the block with relief valve facing down. Fit the 8T4178 Bolt and 8T4121 Washer through the inside of the frame then add the 8T4133 Nuts and tighten.

4. Fit the 4K1388, 6EO358, and 5K9090 O-rings to the adapter and install into the top of the backhoe valve and tighten. Install the 6V8634 Connector and 3K0360 O-ring into the adapter on the backhoe valve and tighten. Fit the 6V8397 O-ring into the connector.

5. Connect a 1226889 Hose, 69 cm long with 1242148 and 1242117 Connectors to the top connector in the backhoe valve (leave elbow end loose). Route the hose behind the backhoe valve tubes/hoses to reduce the chance of chaffing.

6. Connect the other end to the top connection of the valve block on the frame and tighten all the connections without inducing any twisting or strain on the hose (see Illustration 9).

7. Finally fit an 1226890 Hose, 69 cm long with 1242114 and 1242144 Connectors to the connector in the relief valve port of the backhoe valve and the straight connection of the hose to front connection of the valve block and tighten as before (see Illustration 9).

8. Refit the wheel, place the machine in the roading position and check the Hydraulic oil level, then test the machine.

NOTE: It is necessary to bleed the air from the system. Perform this task by placing the machine up on the stabilizers, then extend the boom and stick to full extension. Set engine speed to at least 1500 Rpm. Use the swing lever to swing the boom back and forth at least ten times each direction. This will blow the relief valves and purge the air from the system.

Rework Part 3 - For Groups 1, 2, And 3

In addition to the troubleshooting guide, perform the following steps:

1. Remove/Inspect Spool Centering Hardware for Binding (See Illustration 11).

* Remove 4T4532 Housing on underside of swing section to expose centering hardware.

* Inspect inside surfaces of housing for polishing or evidence of binding. Use a flapper wheel to increase inside diameter by 0.5 mm.

* Remove and inspect 4T4521 Retainers and 9X2027 Washer for burrs, sharp edges. Deburr if necessary.

* Inspect stepped-down diameter on bottom of spool for nicks, rough edges or surfaces.

2. Remove main control spool from swing section.

* Disconnect swing control linkage from top of spool, remove 4T4524 dust guard.

* Pull spool up slightly.

* Reach inside bottom of spool and remove 7F8607 O-ring (otherwise spool will cut O-ring during removal and cause future leakage problems).

* Pull spool down through bottom of valve.

3. Install new swing spool and spool retainer hardware.

* Slide 1486518 Spool into valve from bottom. Push spool up until 7F8607 O-ring can be replaced. Replace O-ring then gently slide spool back down.

* Reinstall spool centering hardware (retainers, washer, spring). Push both retainers and compress the centering spring to make sure nothing is binding. Reinstall the housing with bolts 'finger tight'.

* Operate the spool several times in both directions to insure housing is centered.

* Tighten the bolts to 6 ft lb.Do not overtighten.

* Recheck that spool moves freely and fully returns to center from both directions.

4. Repairs are now complete. Cycle machine several times to flush out air.

1394157 Block Mounting Installation

Illustration 2

Front View - Block Installation

Illustration 3

Illustration 4

Illustration 5

Illustration 6

Illustration 7

Illustration 8

Illustration 9

For Group 2 Only

Illustration 10

Illustration 11