Skip to main content

SERIES 638 CYLINDER HEAD

The Turbotronic 638 engine has six independent aluminum cylinder heads. The cylinder head combines intake and exhaust valve porting with water jacketing to cool the ports, combustion chamber, and related components. ‪

With the independent design, the cylinder head assembly includes: ‪

  • Rocker arm assembly
  • Intake and exhaust valves
  • Glow plug
  • Sensor units
  • Injector nozzles

Repair or Replacement of Cylinder Head

To determine if replacement or repair of the cylinder head is necessary, perform the following procedure. See Figure 28395 . ‪

Flowchart for Replacement or Repair of Cylinder Head

Removal of Cylinder Head

Remove the cylinder head(s) as follows: ‪

  1. Remove rocker covers. Refer to section and refer to section .
  2. Remove intake manifold. Refer to section .
  3. Remove exhaust manifold. Refer to section .
  4. Remove water manifold. Refer to section .
  5. Remove exterior oil feed line. Refer to section .
  6. Remove the fuel nozzle from the cylinder head. Repeat step for each cylinder head. Refer to section .
  7. Remove rocker arm assembly. Refer to section .
  8. Remove twenty six cylinder head bolts securing the cylinder heads to the cylinder block. See Figure 28393 .

    Note: The bolts at either end of the engine also retain the end plates. When removing the bolts use care not to drop the end plates.

    1.Support Plate ‪

    5.Bolt, 12 pt ‪

    2.Bolt, 12 pt ‪

    6.Head Intermediate Clamp ‪

    3.Head End Plate Clamp ‪

    7.Bolt, 12 pt ‪

    4.Head Clamp/Manifold Side ‪

    8.Cylinder Head Gasket ‪

    Cylinder Head Attaching Hardware

Cleaning of Cylinder Head

Clean the cylinder head surface as follows: ‪

  1. Remove old gasket material from the cylinder head(s) surface.

    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 cylinder head with clean fuel oil and blow dry with compressed air.
Inspection of Cylinder Head

Inspect the cylinder head(s) as follows: ‪

  1. Visually check cylinder head for cracks.
    1. If cracks are present, replace the cylinder head. Refer to section .
    2. If cracks are not present, proceed with step of inspection.
  2. Measure cylinder head for flatness.
    1. If cylinder head is not flat, replace the cylinder head. Refer to section .
    2. If cylinder head is flat, proceed with step of inspection.
  3. Visually check cylinder head for coolant leaks.
    1. If cylinder head has coolant leaks, replace the cylinder head. Refer to section .
    2. If cylinder head has no coolant leaks, proceed with step of inspection.
  4. Visually check rocker arm pedestal seating surface for nicks, burrs, and distortions.
    1. If the rocker arm pedestal seating surface has any nicks, burrs, and distortions, replace the cylinder head. Refer to section .
    2. If the rocker arm pedestal seating surface has no nicks, burrs, and distortions, proceed with step of inspection.
  5. Visually check the valve springs for cracks.
    1. If the valve springs are cracked, replace the cylinder head. Refer to section .
    2. If the valve springs are not cracked, reuse the cylinder head. Refer to section .
  6. Visually check the valves for burning or guttering.
    1. If the valves are burnt or guttered, replace the cylinder head. Refer to section .
    2. If the valves are not burnt or guttered, proceed with step of inspection.
  7. Visually check the valve sealing surface by filling the intake and exhaust ports with clean solvent.
    1. If the valve sealing surface is severely leaking solvent, replace the cylinder head. Refer to section .
    2. If the valve sealing surface is leaking a minimal amount of solvent, Refer to section .

Installation of Cylinder Head

Install the cylinder head as follows: ‪

  1. Set the number one piston to top-dead-center.
  2. Place J 22273-01 on the cylinder block and set the gage to zero. See Figure 28651 .

    Piston Height Measurement

  3. Slide the dial gage onto the piston and record the measured dimension. Select a suitable head gasket thickness as listed in Table and see Figure 28652 for gasket thickness identification.

    Measured Dimension

    Head Gasket Thickness

    0.53-0.62 mm (0.020-0.024 in.) ‪

    1.42 mm (0.055 in.) ‪

    0.63-0.72 mm (0.024-0.028 in.) ‪

    1.52 mm (0.059 in.) ‪

    0.73-0.82 mm (0.028-0.032 in.) ‪

    1.62 mm (0.063 in.) ‪

    Cylinder Head Gasket Thickness

    Gasket Thickness Identification

  4. Install cylinder head guide studs VM1009, into the cylinder block.
  5. Install the cylinder head(s) to the cylinder block.

    Note: Install cylinder head(s) in the following order: number 1 through number 6.

  6. Install center cylinder head bolts and clamp-head brackets to the cylinder head(s). See Figure 28393 .

    Note: Apply lubricating oil to the head bolt threads and the underside of the bolt head.

    1.Support Plate ‪

    5.Bolt, 12 pt ‪

    2.Bolt, 12 pt ‪

    6.Head Intermediate Bolt ‪

    3.Head Manifold Side Clamp ‪

    7.Bolt, 12 pt ‪

    4.Front Head Clamp ‪

    8.Cylinder Head Gasket ‪

    Cylinder Head Attaching Hardware

  7. Loosely install end cylinder head bolts and both the front and rear support plate. Torque cylinder head bolts; refer to section .
  8. Run the engine to verify repair.
Cylinder Head Torque Sequence

Perform the following to properly torque the cylinder head(s): ‪

  1. Torque bolts 1 through 14 to 30 N m (22 lb ft) and see Figure 28197 for proper torque sequence.

    Cylinder Head Torque Sequence

  2. Angle torque bolts 1 through 14 to 705.
  3. Angle torque bolts 1 through 14 an additional 705.
  4. Torque bolts 15 through 26 to 30 N m (22 lb ft).
  5. Angle torque bolts 15 through 26 to 80-905.

    To avoid personal injury, before starting and running the engine, be sure that the vehicle is parked on a level surface and that the wheels are properly blocked. ‪

  6. Run engine for 20 minutes.
  7. Shut down the engine and allow to cool.
  8. Loosen and torque bolts 1 through 14 to 30 Nm (22 lbft) and angle torque to 130.
  9. Torque bolts 15 through 26 to 90 Nm (66 lbft).