Machine Preparation
- Move the machine to a smooth horizontal location. Move away from working machines and personnel. Lower the work tools to the ground.
- Allow only one operator on the machine. Keep all personnel away from the machine or in the view of the operator.
- Engage the parking brake.
Performance Test
Stall Test
The torque converter stall test is designed to test the engine, the torque converter, the drive train and the brake system as a unit. The torque converter output is stalled while the engine is operated at high idle. The speed of the engine at torque converter stall indicates whether the engine and the transmission are operating correctly under full load.
If the engine speed is lower than the normal given speed or if the engine speed is higher than the normal given speed, this indicates that there is a problem in the engine or in the transmission. If testing shows correct engine performance but the torque converter stall speed is not correct, the problem is in the torque converter or in the transmission.
Reference: To check the performance of the Caterpillar 3176C Engine, refer to the following service literature: Specifications, SENR9527, "3176Cand 3196 Engine For Caterpillar Built Machines" and Systems Operation, Testing and Adjusting, SENR9528, "3176Cand 3196 Engine For Caterpillar Built Machines".
Perform the torque converter stall test.
Reference: For information on performing the torque converter stall test, refer to the Service Manual module Testing and Adjusting, "Torque Converter Stall and Implement Pump Double Stall - Test" for the machine that is being serviced.
Low stall speeds indicate a possible problem with engine performance. The stall speed should be corrected before the performance of the implement pump can be properly tested.
Implement Cycle Time
The cycle time of the implements is affected by the amount of oil flow that is produced by the implement pump. Check the implement cycle times in order to determine if there may be a problem with the implement pump.
- Perform the machine preparation for testing.
- Warm the hydraulic oil to normal operating temperature.
- Ensure that the hydraulic lockout valve is in the UNLOCK position.
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| Illustration 1 | g00892557 |
Hydraulic System Controls (A) LOCK position. (B) UNLOCK position. | |
- Begin the test for the lift cycle time with the work tool flat on the ground.
- Increase the engine speed to high idle.
- Pull the lift control lever back to the full RAISE position. Measure the lift cycle time. Record the lift cycle time.
- Move the lift arms to the full RAISE position.
- Move the work tool to the full TILTBACK position.
- Move the tilt control lever to the full DUMP position. Measure the cycle time for dump. Record the cycle time for dump.
- Lower the lift arms and place the work tool flat on the ground.
- Reduce engine speed to low idle.
- Turn the engine start switch to the OFF position.
| Cycle Times (oil at normal operating temperature) | |||
| Machine | Machine Function | Time in Seconds | |
| 966G II | Lift with empty work tool | 6.9 ± 0.5 | |
| Dump | 2.0 ± 0.5 | ||
| 972G II | Lift with empty work tool | 6.9 ± 0.5 | |
| Dump | 1.7 ± 0.5 | ||
Compare the test results with the cycle times that are listed in Table 1. The implement pump should be working properly if the implement cycle times match the cycle times that are listed in Table 1.
Possible Causes for Incorrect Times
If the cycle times are not correct for both the lift and dump functions one of the following conditions are present:
- The pressure setting of the main relief valve is not within specifications.
- The pump may have excessive wear.
The main relief pressure should be tested. If the main relief pressure is low, the cycle times should be retested after the adjustment to the main relief valve.
Reference: For more information on testing and adjusting the main relief valve, refer to the Service Manual module Testing and Adjusting, "Relief Valve (Main) - Test and Adjust" for the machine that is being serviced.
If the cycle time is slow for only one of the implement circuits, the circuit with slow cycle time should be tested for one of the following conditions:
- Low relief valve setting
- Leak in the circuit
- The spool in the main control valve is not fully shifted.
Reference: For more information on troubleshooting the hydraulic system, refer to the Service Manual module Testing and Adjusting, "Hydraulic System Troubleshooting" for the machine that is being serviced.