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SERIES 638 ROCKER COVERS

The Turbotronic 638 uses two separate rocker covers that are constructed of cast aluminum. Each rocker cover is secured with three retaining bolts and has caps that can be removed to torque the cylinder heads without having to remove the rocker cover. ‪

Replacement of Rocker Covers

To determine if replacement of the rocker covers is necessary, perform the following procedure. See Figure 21694 . ‪

Flowchart for Replacement of Rocker Covers

Removal of Front Rocker Cover

Remove the front rocker cover as follows: ‪

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. ‪

  1. Preclean the front rocker cover to keep dirt and debris out of the valve gear chamber using clean fuel oil and blow dry with compressed air.
  2. Unplug glow plug harness at the glow plugs. See Figure 27771 .

    1.Glow Plug ‪

    2.Glow Plug Harness ‪

    Glow Plug Harness Removal

  3. Remove center plug from between the rocker covers. See Figure 27772 .

    1.Plastic Plugs ‪

    Front Rocker Cover Center Plastic Plug Removal

  4. Remove oil fill tube. See Figure 27773 .

    1.Clamp ‪

    2.Oil Fill Tube ‪

    Oil Fill Tube Removal

  5. Remove three front rocker cover retaining bolts. See Figure 27774 .

    1.Retaining Bolts (3) ‪

    Front Cover Retaining Bolts Removal

  6. Remove front rocker cover and gasket from the cylinder heads.
Cleaning of Front Rocker Cover

Clean the front rocker cover as follows: ‪

  1. Remove old gasket material from front rocker cover surfaces.

    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. Cleanse the front rocker cover with clean fuel oil and blow dry with compressed air.
Inspection of Front Rocker Cover

Inspect the front rocker cover as follows: ‪

  1. Visually check the rocker cover for cracks or warpage.
    1. If the front rocker cover has cracks or warpage, replace the component. Refer to section .
    2. If the front rocker cover has no cracks or warpage, reuse the component. Refer to section .

Installation of Front Rocker Cover

Install the front rocker cover as follows: ‪

  1. Install front rocker cover and new gasket to the cylinder heads with three retaining bolts. Torque bolts to 15 N m (11 lb ft). See Figure 27781 .

    1.Cylinder Block ‪

    4.Front Rocker Cover ‪

    2.Cylinder Head ‪

    5.Front Cover Retaining Bolts ‪

    3.Front Rocker Cover Gasket ‪

    Front Rocker Cover and Gasket Installation

  2. Install oil fill tube. Refer to OEM guidelines.

    NOTICE:

    Plugs must be installed during operation of the engine to ensure that dirt and debris will not fill the access holes. ‪

  3. Install front rocker cover plugs, if removed.
  4. Reconnect glow plug harness connectors to the glow plugs. See Figure 27771 .

    1.Glow Plug ‪

    2.Glow Plug Harness ‪

    Glow Plug Harness Connector

  5. Run the engine to verify repair.

Removal of Rear Rocker Cover

Remove rear rocker cover as follows: ‪

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. ‪

  1. Preclean the rear rocker cover to keep dirt and debris out of the valve gear chamber using clean fuel oil and blow dry with compressed air.
  2. Unplug glow plug harness at the glow plugs. See Figure 27775 .

    1.Glow Plug ‪

    2.Glow Plug Harness ‪

    Glow Plug Harness Removal

  3. Remove center plastic plug between front and rear valve covers, if necessary. See Figure 27776 .

    1.Plastic Plugs ‪

    Removal of Rear Rocker Cover Center Plastic Plug

  4. Remove crankcase breather hose. See Figure 27777 .

    1.Clamp ‪

    2.Breather Hose ‪

    Crankcase Breather Hose Removal

  5. Remove three rear rocker cover retaining bolts. See Figure 27950 .

    1.Rocker Cover Retaining Bolts ‪

    Rear Rocker Cover Retaining Bolt Removal

  6. Remove rear rocker cover and gasket from the cylinder heads. See Figure 27950 .
Cleaning of Rear Rocker Cover

Clean the rear rocker cover as follows: ‪

  1. Remove old gasket material from rear rocker cover surfaces.

    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. Cleanse rear rocker cover with clean fuel oil and blow dry with compressed air.
Inspection of Rear Rocker Cover

Inspect the rear rocker cover as follows: ‪

  1. Visually check the rear rocker cover for cracks or warpage.
    1. If the rear rocker cover has cracks or warpage, replace the component. Refer to section .
    2. If the rear rocker cover has no cracks or warpage, reuse the component. Refer to section .

Installation of Rear Rocker Cover

Install the rear rocker cover as follows: ‪

  1. Install rear rocker cover and new gasket to the cylinder heads with three retaining bolts. Torque bolts to 15 N m (11 lb ft).
  2. Install crankcase breather hose. See Figure 27777 .

    1.Clamp ‪

    2.Breather Hose ‪

    Crankcase Breather Hose Installation

  3. Install rear rocker cover center plugs, if removed. See Figure 27776 .

    1.Plastic Plugs ‪

    Rear Rocker Cover Plastic Plugs Installation

  4. Reconnect glow plug harness connectors to the glow plugs. See Figure 27775 .

    1.Glow Plug ‪

    2.Glow Plug Harness ‪

    Glow Plug Harness Installation

  5. Run the engine to verify repair.