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Pinpoint Test T: The Front Axle Makes Noise In 2H Mode Only And Generally Under Heavy Throttle

WARNING: This page is about a different car, the 2012 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
  1. T1 CHECK FOR GRINDING NOISES AT HIGH SPEEDS 
    WARNING: When directed to drive the vehicle as part of this test, drive the vehicle on a hard surface in an area without traffic to prevent a crash. Failure to follow these instructions may result in personal injury.
    • With the vehicle warm and the MSS in 2H mode, drive the vehicle at sustained WOT for 5 seconds.
    • Is there a grinding noise from the axle system during WOT? 
      • Yes  : GO to  T2.
      • No  : IDENTIFY the customer concern and GO to the Symptom Charts .
  2. T2 CHECK THE IWE SOLENOID OUTPUT VACUUM IN 2H 
      NOTE: The engine must be idling during the following steps to supply vacuum to the IWE solenoid.
    • Start the engine.
    • Disconnect the output vacuum line at the IWE solenoid while having the vacuum supply attached to the solenoid.
    • With the engine running and the in 2H mode, measure the vacuum at the output port of the solenoid.
    • Is the vacuum greater than 254 mm (10 in) Hg? 
      • Yes  : GO to  T7.
      • No  : GO to  T3.
  3. T3 CHECK THE IWE SOLENOID INPUT VACUUM 
    • Disconnect the supply vacuum line at the IWE solenoid.
    • With the engine still running, measure the supply line vacuum to the IWE solenoid.
    • Is the vacuum greater than 254 mm (10 in) Hg? 
      • Yes  : INSTALL a new IWE solenoid. TEST the system for normal operation.
      • No  : GO to  T4.
  4. T4 CHECK SOURCE VACUUM TO THE VACUUM RESERVOIR 
    • Disconnect the source vacuum line from the vacuum reservoir.
    • With the engine still running, measure the source vacuum being supplied to the vacuum reservoir.
    • Is the vacuum greater than 254 mm (10 in) Hg? 
      • Yes  : GO to  T5.
      • No  : REPAIR or INSTALL a new source vacuum line. TEST the system for normal operation.
  5. T5 CHECK THE VACUUM RESERVOIR 
    • Ignition OFF.
    • Disconnect the vacuum line from the vacuum reservoir.
    • Connect a hand vacuum pump to the source vacuum port on the vacuum reservoir and apply 508 mm (20 in) Hg of vacuum.
    • Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute? 
      • Yes  : GO to  T6.
      • No  : INSTALL a new vacuum reservoir. TEST the system for normal operation.
  6. T6 CHECK THE ONE-WAY VACUUM CHECK VALVE 
      NOTE: The check valve is between the IWE solenoid and the vacuum reservoir.
    • Connect the vacuum lines to the IWE solenoid.
    • Connect a hand vacuum pump to the IWE solenoid vacuum line at the vacuum reservoir and apply 508 mm (20 in) Hg of vacuum.
    • Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute? 
      • Yes  : Concern not present at this time. CARRY OUT the Four-Wheel Drive (4WD) System Functional Test. GO to Pinpoint Test U .
      • No  : REPAIR or INSTALL new vacuum lines or INSTALL a new one-way check valve. TEST the system for normal operation.
  7. T7 CHECK THE IWE VACUUM SYSTEM 
    • Ignition OFF.
    • Disconnect both vacuum lines from the IWE solenoid.
    • Using a hand vacuum pump, apply 508 mm (20 in) Hg of vacuum to the IWE system through the apply vacuum circuit.
    • Observe the vacuum reading.
    • Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute? 
      • Yes  : CONNECT the vacuum lines to the solenoid. GO to  T11.
      • No  : GO to  T8.
  8. T8 CHECK THE RH IWE LEAK RATE 
    • With the vehicle in NEUTRAL, position it on a hoist. REFER to JACKING & LIFTING .
    • Disconnect the vacuum line from the larger port on the RH IWE.
    • Apply 508 mm (20 in) Hg of vacuum to the RH port and observe vacuum reading.
    • Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute? 
  9. T9 CHECK THE LH IWE LEAK RATE 
    • Disconnect the vacuum line from the larger port at the LH IWE.
    • Apply 508 mm (20 in) Hg of vacuum to the LH port and observe vacuum reading.
    • Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute? 
  10. T10 CHECK THE IWE VACUUM SUPPLY TUBE 
    • Disconnect both vacuum lines from the IWE solenoid.
    • Plug both LH and RH IWE vacuum lines. Apply 508 mm (20 in) Hg of vacuum to the IWE apply vacuum circuit and observe the vacuum reading.
    • Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute? 
      • Yes  : GO to  T11.
      • No  : INSTALL new vacuum lines as necessary. TEST the system for normal operation.
  11. T11 CHECK THE IWE VACUUM SUPPLY AT EACH IWE IN 2H 
    • Connect a hand-held vacuum gauge to the LH vacuum supply tube.
      • NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWE to engage and disengage.
    • Start the engine.
    • Switch the to 2H mode while observing the vacuum gauge.
    • Repeat these steps for the RH IWE.
    • Are the vacuum readings greater than 254 mm (10 in) Hg? 
      • Yes  : GO to  T12.
      • No  : INSTALL new vacuum lines as necessary. TEST the system for normal operation.
  12. T12 CHECK THE LH IWE VACUUM LINE FOR AN OBSTRUCTION 
    • Ignition OFF.
    • Disconnect both vacuum lines from the IWE solenoid.
    • With the vehicle in NEUTRAL, position it on a hoist. REFER to JACKING & LIFTING .
    • Disconnect the vacuum line at the LH IWE.
    • Connect a hand vacuum pump to the LH IWE vacuum line and attempt to draw a vacuum on the line.
    • Did the hand vacuum pump draw a vacuum on the LH IWE vacuum line? 
      • Yes  : INSTALL a new vacuum line. TEST the system for normal operation.
      • No  : CONNECT the vacuum line to the LH IWE. GO to  T13.
  13. T13 CHECK THE RH IWE VACUUM LINE FOR AN OBSTRUCTION 
    • Disconnect the larger vacuum line at the RH IWE.
    • Connect a hand vacuum pump to the RH IWE vacuum line and attempt to draw a vacuum on the line.
    • Did the hand vacuum pump draw a vacuum on the RH IWE vacuum line? 
      • Yes  : INSTALL a new vacuum line. TEST the system for normal operation.
      • No  : CONNECT the vacuum line to the RH IWE. GO to  T14.
  14. T14 CHECK THE LH IWE OPERATION 
    • Ignition OFF.
    • Connect a hand vacuum pump with gauge to the larger port of the LH IWE.
    • Observe the LH halfshaft while rotating the LH front tire. Apply between 152 and 203 mm (6 to 8 in) Hg of vacuum and release the vacuum to manually disengage and engage the LH IWE.
    • Did the LH IWE disengage between 152 and 203 mm (6 to 8 in) Hg and engage when the vacuum is released? 
  15. T15 CHECK THE RH IWE OPERATION 
    • Connect a hand vacuum pump with gauge to the larger port of the RH IWE.
    • Observe the RH halfshaft while rotating the RH front tire. Apply between 152 and 203 mm (6 to 8 in) Hg of vacuum and release the vacuum to manually disengage and engage the RH IWE.
    • Did the RH IWE disengage between 152 and 203 mm (6 to 8 in) Hg and engage when the vacuum is released? 
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