Troubleshooting Steering Alignment Issues on certain Caterpillar Branded Telehandlers.

Transcription

1 Publication date 30/06/2011 (Revised 01/07/2011) July 1, 2011 Troubleshooting Steering Alignment Issues on certain Caterpillar Branded Telehandlers. Note: This revised special instruction replaces the 30 June 2011 special instruction. Label details of the caption for figure D and E has been corrected. Introduction: This special instruction provides information for testing and troubleshooting steering alignment issues on certain Cat branded Telehandlers. Applicable to: Special Instruction Reference: SI 1103 These troubleshooting guidelines are applicable to Caterpillar Branded Telehandlers with the following serial numbers: Model TH336 TH337 TH406 TH407 TH414 TH514 TH417 Applicable Serial Number Range TDE00100 Up TDF00100 Up TBX00100 Up TBY00100 Up TBZ00100 Up TBW00100 Up TBT00100 Up Acceptance Criteria: The acceptance criteria should only be used as a guideline to determine if further troubleshooting needs to occur. Due to steering drift being impacted by work tool selection, various job site conditions, user application etc., it is necessary for operators perform the following checks to ensure the steering system is able to function properly. The steering must be aligned: At the start of each work shift. Once during each work shift. If steering difficulty occurs. Before road traveling. If the machine has traveled 24KM (15miles) on a public road in two-wheel steer (2WS) mode. Page 1 of 8

2 It is common for steer drift to occur with machines offering All-Wheel Steer (AWS) options. It is determined that a maximum of 5 misalignment per four (4) hour work shift is acceptable. Note: It is important that operators do not turn the steering wheel after the ignition is turned to the off position. This will lead to steering misalignment, which will result in reduced accuracy of the steering system. Testing Procedure: Use the following guidelines to test the machine. This will ensure there is an unacceptable condition with the steering system before replacing parts. 1) Preparation for Testing: No attachments or work tools to be fitted. Test should be conducted on a flat and hard surface. Ensure the engine is at normal operating temperature. Steering system must be bled prior to test. Tests 1, 2 & 3 are to be conducted in 2nd gear and Four-Wheel Steer (4WS) mode. 2) Steer Bleed Procedure: The steering system must be purged of any air prior to performing any tests. Please follow as instructed below: 1. Centre wheels 2. Select manual steer mode 3. 4WS Turn left (select 2WS if required to reach front axle stops) 4. 2WS Turn right 5. Crab Turn left 6. 2WS Turn right & turn left & turn right 7. 4WS Turn left 8. 2WS - Turn right & turn left & turn right 9. Crab Turn left 10. 2WS - Turn right & turn left & turn right 11. 4WS Turn left 12. 2WS - Turn right & turn left & turn right 13. Crab Turn left 14. 2WS - Turn right & turn left & turn right 15. 4WS Centre wheels 16. Done Page 2 of 8

3 3) Steer Alignment Procedure: To ensure the most accurate results it is important to correctly align the wheels prior to any testing. To achieve the maximum accuracy, the wheels should be aligned using the following instructions: Equipment required: - Tape measure - String (approx 5 meters) - Notepad to record results 1) Park machine on a flat/ level surface. 2) Centralize the wheels. 3) Attach string to rear axle steer stop as shown (Figure A). 4) Attach other end of string to front axle steer stop and pull tight. 5) Select manual steer mode. 6) Using the string as a guide, position the front and rear wheels in a straight position (it will be necessary to switch between 4WS and 2WS to attain an accurate result). 7) When wheels are straight, look down the line of the string it should touch the outer walls or each tire. There should be no apparent deflections in the string (Figure B). 8) Ensure machine is set now to 4WS mode, but remain in manual alignment mode. 9) Record the measurement of the front (cab side) steer rod as shown (Figure C). 10) Now measure the hub offset from the tire as shown (Figure D) and record the result. 11) Remove the string completely from the machine. 12) The wheels are now accurately aligned and ready for testing. Figure A Figure B Page 3 of 8

4 Figure C Figure D Figure E 4) Steer Alignment Measurement: Steering misalignment should be measured after each of the following tests, and the results recorded on the data sheets provided. Use the following instructions to measure steering misalignment: 1) Park machine on a flat surface. 2) Straighten wheels and check steer rod displacement with tape measure. Adjust the steering to match the figure previously recorded (Figure C). 3) Any steer misalignment should now be noticeable by looking at the back wheels. 4) Connect string to rear axle steer stop and pull tight ensuring a straight line as shown (Figure E). 5) Use tape measure to measure distance between string and hub as shown (Figure E). 6) Record results on sheet. 7) When results are calculated the wheels can be re-aligned using the wheel alignment procedure. Page 4 of 8

5 Steer Alignment Testing #1: 1) Mark out a track as shown below Marker points 10 meters 2) Drive 50 laps of the circuit, hitting full lock on each turn. Use 4WS and 2nd gear 3) Record results (see Record Sheet Test 1) 4) Realign wheels ready for next test (see Steering Alignment Procedure). Record Sheet - Test #1: Page 5 of 8

6 Steer Alignment Test #2: 1) Mark out a course as shown below: 2) Drive 50 cycles of the circuit, hitting full lock on each turn. Use 4WS and second gear. 3) Record results (see Record Sheet Test 2) 4) Realign wheels ready for next test (see Steering Alignment Procedure). Record Sheet - Test #2: Page 6 of 8

7 Steer Alignment Test #3: 1) Mark out a course as shown below: 2) Drive 50 cycles of the circuit, hitting full lock on each turn. Use 4WS and second gear. 3) Record results (see Record Sheet Test 3) 4) Realign wheels ready for next test (see Steering Alignment Procedure). Record Sheet - Test #3: Page 7 of 8

8 Steer Alignment Test #4: Test 4 is designed to simulate the customers usage. Please speak with the customer and try to replicate their usage which they feel introduces steer misalignment. This may include gear changes, boom operation and lifting loads. 1) Keep machine in 4WS mode for the test. 2) Suggested that this test should last 2 hours. 3) Measure steering misalignment. Trouble Shooting Guidelines: The following guidelines should be followed in order to properly diagnose an excessive steer drift condition. This guideline is designed to troubleshoot possible root causes before any replacement of major components. The following should occur in sequential order. This is to reduce the cost and time associated with replacing parts which are not faulty. 1. Check the below steering system components for leaks. Ensure that the hydraulic system is at normal operating temperature before inspection. Replace leaking parts as necessary. a. Steering Valve. b. Hydraulic Lines. c. Steering Rods. 2. Verify the position of the steering sensor on the axle. 3. Verify there is no air in the hydraulic system. Although most significant steering misalignment conditions can be resolved per the above troubleshooting, there may need to be part replacement to properly resolve severe steering drift issues. If the unit has failed the steering alignment measurement tests above and no root cause can be found through this troubleshooting guideline, then component replacement may be required. We recommend the replacement and retesting of the unit after each component is replaced. The recommended order of replacement is the following: 1. Steering Sensor. 2. Steering Valves. 3. Steering Cylinders. Page 8 of 8