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SERIES 638 VACUUM PUMP

The Turbotronic 638 vacuum pump provides a source of vacuum for the Air Gas Recirculator (AGR) valve or any component requiring a vacuum source. Vacuum is produced by sliding vanes within the vacuum pump which is gear driven. ‪

Replacement of Vacuum Pump

To determine if replacement of the vacuum pump is necessary, perform the following procedure. See Figure 28399 . ‪

Flowchart for Replacement of Vacuum Pump

Removal of Vacuum Pump

Remove the vacuum pump as follows: ‪

  1. Remove front cover assembly. Refer to section .
  2. Rotate the engine until the camshaft gear holes align with thrust plate retaining screws. See Figure 28400 .

    1.Allen Head Bolt ‪

    2.Camshaft Drive Gear ‪

    Thrust Plate Retaining Screws Location

  3. Mark the camshaft and crankshaft gears-to-vacuum pump gear.
  4. Remove the thrust plate retaining screws.
  5. Slide camshaft out 1/4 in. from the cylinder block.
  6. Remove three Allen head retaining bolts from vacuum pump.

    Note: Mark the bolt, located at the 2 o'clock position, to ensure that the vacuum pump oil supply is not restricted during engine operation.

  7. Remove the vacuum pump from the vacuum pump bore.
Cleaning of Vacuum Pump

Clean the vacuum pump as follows: ‪

  1. Remove any dirt or debris from the vacuum pump using clean fuel oil.

    To avoid personal injury when blow drying, wear adequate eye protection (safety glasses or face plate) and do not exceed 276 kPa (40 lb/in. 2 ) air pressure. ‪

  2. Dry vacuum pump with compressed air.
Inspection of Vacuum Pump

Inspect the vacuum pump as follows: ‪

  1. Visually check the vacuum gear teeth for damage.
    1. If the gear teeth are damaged, replace the component. Refer to section .
    2. If the gear teeth are not damaged, proceed with step of inspection.
  2. Manually test the spring tension between the double gears to ensure free movement.
    1. If the double gears cannot move freely, replace the component. Refer to section .
    2. If the double gears can move freely, proceed with step of inspection.
  3. Visually check the vacuum pump sliding vanes for cracks and broken teeth.
    1. If the vacuum pump vanes are cracked or broken, replace the component. Refer to section .
    2. If the vacuum pump vanes are not cracked or broken, reuse the component. Refer to section .

Installation of Vacuum Pump

Install the vacuum as follows: ‪

  1. Place the vacuum pump into the vacuum pump bore.
  2. Install three Allen head retaining bolts to secure the vacuum pump. Torque to 27-28 N m (20-21 lb ft).
  3. Slide camshaft into the cylinder block.
  4. Align camshaft and crankshaft gears-to-vacuum pump gear with mark made during removal. See Figure 28400 .

    1.Allen Head Bolt ‪

    2.Camshaft Drive Gear ‪

    Thrust Plate Retaining Screws Location

  5. Install the thrust plate retaining screws. Torque to 27-28 N m (20-21 lb ft).
  6. Install the front cover. Refer to section .
  7. Run the engine to verify repair.