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Home >> Ford >> 2008 >> Expedition EL RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 1 (Four Wheel Drive (4WD) Systems) >> Diagnostic Tests >> Four Wheel Drive (4WD) Systems - 2-Speed Torque-On-Demand >> Pinpoint Tests >> Pinpoint Test T: The Front Axle Makes Noise in 2H Mode Only and Generally Under Heavy Throttle >> Pinpoint Test T: The Front Axle Makes Noise In 2H Mode Only And Generally Under Heavy Throttle

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

WARNING: This page is about a different variant/trim than selected.
  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? 
    1. YES  : Go to  T2.
    2. NO  : IDENTIFY the customer concern and Go to the Symptom Chart.
  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 MSS in 2H mode, measure the vacuum at the output port of the IWE solenoid.
    • Is the vacuum greater than 254 mm (10 in) Hg? 
    1. YES  : Go to  T7.
    2. 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? 
    1. YES  : INSTALL a new IWE solenoid. TEST the system for normal operation.
    2. 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? 
    1. YES  : Go to  T5.
    2. NO  : REPAIR or INSTALL a new source vacuum line. TEST the system for normal operation.
  5. T5 CHECK THE VACUUM RESERVOIR 
    • Key in OFF position.
    • 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? 
    1. YES  : Go to  T6.
    2. 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? 
    1. YES  : Concern not present at this time. CARRY OUT the Four-Wheel Drive (4WD) System Functional Test. Go to Pinpoint Test u .
    2. 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 
    • Key in OFF position.
    • 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? 
    1. YES  : CONNECT the vacuum lines to the IWE solenoid. Go to  T11.
    2. 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 AND LIFTING article.
    • Disconnect the vacuum line from the larger port on the RH IWE.
    • Apply 508 mm (20 in) Hg of vacuum to the RH IWE port and observe vacuum reading.
    • Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute? 
    1. YES  : Go to  T9.
    2. NO  : INSTALL a new RH IWE. REFER to Integrated Wheel End (IWE) . Go to  T7.
  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 IWE port and observe vacuum reading.
    • Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute? 
    1. YES  : Go to  T10.
    2. NO  : INSTALL a new LH IWE. REFER to Integrated Wheel End (IWE) . Go to  T7.
  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? 
    1. YES  : Go to  T11.
    2. NO  : INSTALL new vacuum lines as necessary. Go to  T7.
  11. T11 CHECK THE IWE VACUUM SUPPLY AT EACH IWE IN 2H 
    • Connect a hand-held vacuum gauge to the LH IWE 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 MSS 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? 
    1. YES  : Go to  T12.
    2. NO  : INSTALL new vacuum lines as necessary. Go to  T7.
  12. T12 CHECK THE LH IWE VACUUM LINE FOR AN OBSTRUCTION 
    • Key in OFF position.
    • Disconnect both vacuum lines from the IWE solenoid.
    • With the vehicle in NEUTRAL, position it on a hoist. Refer to JACKING AND LIFTING article.
    • 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? 
    1. YES  : INSTALL a new vacuum line. TEST the system for normal operation.
    2. 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? 
    1. YES  : INSTALL a new vacuum line. TEST the system for normal operation.
    2. NO  : CONNECT the vacuum line to the RH IWE. Go to  T14.
  14. T14 CHECK THE LH IWE OPERATION 
    • Key in OFF position.
    • With the vehicle in NEUTRAL, position it on a hoist. Refer to JACKING AND LIFTING article.
    • 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? 
    1. YES  : Go to  T15.
    2. NO  : INSTALL a new LH IWE. REFER to Integrated Wheel End (IWE) . TEST the system for normal operation.
  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? 
    1. YES  : Go to Pinpoint Test U .
    2. NO  : INSTALL a new RH IWE. REFER to Integrated Wheel End (IWE) . TEST the system for normal operation.
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