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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. |
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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand. |
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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, "Caterpillar Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates. |
Introduction
The following tests are used to test the modulating valve for the torque converter lockup clutch and the solenoid on this modulating valve.
Prior to starting checks on the modulating valve for the torque converter lockup clutch, use Caterpillar ET in order to diagnose any fault codes that may be present. Refer to Systems Operation, Troubleshooting, Testing and Adjusting, KENR5903, "Power Train Electronic Control System".
Note: The torque converter lockup clutch is engaged during high engine speeds.
Required Tools
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| Illustration 1 | g01704997 |
| Required Tools | |||
|---|---|---|---|
| Tooling | Part Number |
Description | Qty |
| A | 8T-0855 | Pressure Gauge | 1 |
| 6V-3989 | Fitting | 1 | |
| 6V-4143 | Quick Connect Coupler | 2 | |
| 177-7861 | Hose As | 1 | |
Testing Procedure
Testing the Pressure for the Torque Converter Lockup Clutch
- Install Tooling (A) on pressure tap (1) .
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| Illustration 2 | g01309346 |
- Start the engine. Warm up the oil until the oil reaches 47 °C (116 °F).
- Ensure that the transmission control is in the NEUTRAL position.
- Place the transmission control into the FIRST gear position and begin increasing the engine speed. As the engine rpm increases the lockup clutch will engage. Observe the pressure gauge. The torque converter outlet pressure must be within the values that are shown in Specifications, Systems Operation/Testing and Adjusting, "Power Train Pressures".
- If the pressure in 4 is within the specified limit, go to 6. If the pressure in Step 4 is not within the specified limit, go to the testing procedure in "Testing the Operation of the Solenoid on the Modulating Valve".
- Place the transmission control in the NEUTRAL position.
- Stop the engine and allow the pressure to drop to zero. Disconnect Tooling (A) from pressure tap (1) .
Testing the Operation of the Solenoid on the Modulating Valve
Test for a rise in the pressure of the oil in the torque converter lockup clutch when the clutch is selected. Refer to the procedure in "Testing the Pressure for the Torque Converter Lockup Clutch". If a pressure rise is noted, the solenoid and the related electrical circuit are functioning. If a pressure rise is not noted, perform the following testing procedure.
- Use a tag wire to check that the solenoid coil is energized. If the tag wire is attracted to the solenoid coil, this indicates that the solenoid coil is energized. The problem is in the solenoid cartridge. The problem could be a bent solenoid stem, a screen that is dirty or plugged, or a spring that is weak or broken.
- If the tag wire does not indicate that the solenoid coil is energized, the problem is in the electrical circuit.
- If the solenoid does not appear to function, disconnect the connector for the solenoid valve. Check the resistance of the windings of the coil in the solenoid. The resistance of the windings in the solenoid should be 8.7 Ohms ± 0.4 Ohms.
- If the resistance of the windings is outside the specifications replace the solenoid.