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MBE 4000 ENGINE BRAKE

Engine braking is controlled by a pneumatically-operated exhaust brake on the turbocharger in conjunction with constant-throttle valves on the cylinder head. The exhaust back-pressure is used by the exhaust brake to increase braking performance. The constant-throttle valves use the air that escapes through them on the compression stroke to provide braking force. ‪

The constant throttles are small valves which are built into the cylinder heads and positioned opposite the exhaust valves. When open, a link is created between the combustion chamber and the exhaust port. When the engine brake is switched on, the constant-throttle valves are opened by pneumatic pressure. ‪

Note: When in emergency running mode (constant rpm), the engine brake can be activated only when the engine is in overrun. When constant rpm has been attained, the engine brake is automatically turned off.

For greater braking power, an optional turbo brake is available. ‪

Constant-Throttle Valve Removal

Remove the constant-throttle valve as follows: ‪

  1. Remove the cylinder head. Refer to section .
  2. Remove the injector nozzle. Refer to section .
  3. From the top of the cylinder head, remove the end cover on the constant-throttle valve. See Figure 41924 .

    1. End Cover ‪

    7. Spring ‪

    2. O-ring ‪

    8. Spring Guide ‪

    3. Piston Seal ‪

    9. Valve Stem Seal ‪

    4. Piston ‪

    10. Valve ‪

    5. Collets ‪

    11. Cylinder Head ‪

    6. Spring Retainer ‪

    Constant-Throttle Valve (exploded view)

    Note: Insert a spacer beneath the valve head to prevent the valve from opening while doing the rest of the removal procedures. See Figure 41925 .

  4. From the bottom of the cylinder head, insert a suitable spacer about 6.0 mm (1/4 inch) in height. See Figure 41925 .

    1. End Cover ‪

    7. Spring ‪

    2. O-ring ‪

    8. Spring Guide ‪

    3. Piston ‪

    9. Valve Stem Seal ‪

    4. Piston Seal ‪

    10. Valve ‪

    5. Collets ‪

    11. Spacer ‪

    6. Spring Retainer ‪

    Constant-Throttle Valve (cutaway view, with spacer installed)

  5. Using needle-nose pliers, remove the piston. Pull the piston and piston seal out of the valve bore. See Figure 41926 .

    1. Needle-Nose Pliers ‪

    2. Piston ‪

    Removing the Piston

  6. Inspect the piston and piston seal for damage and signs of wear. If necessary, replace the piston and piston seal.
  7. Insert the constant-throttle valve (CTV) spring remover (442 589 05 63 00) down onto the spring retainer. Remove the collets with a magnetic pin. See Figure 41927 .

    1. Collets ‪

    3. Spring ‪

    2. Spring Retainer ‪

    Compressing the Spring

  8. Relieve the pressure on the spring. Remove the spring retainer, spring and spring guide. For ease of installation, mark the spring retainer and spring guide with a paint pen.
  9. Turn over the cylinder head. From the bottom of the cylinder head, draw out the valve and spacer. For ease of installation, mark the valve with a paint pen.
  10. Using a small hook, remove and discard the valve stem seal.

    Note: Always replace the valve stem seal whenever the constant-throttle valve is removed.

  11. Repeat this procedure for each constant-throttle valve.

Constant-Throttle Valve Installation

Install the constant-throttle valve as follows: ‪

  1. Lubricate the valve stem with a light coating of clean engine oil. From the bottom of the cylinder head, push the valve, as marked on removal, into the valve bore. See Figure 41924 .

    Note: Insert a spacer beneath the valve head to prevent the valve from opening while installing the valve spring and piston.

  2. Insert a suitable spacer about 6.0 mm (1/4 inch) in height. See Figure 41925 .
  3. Install a new seal on the valve stem.
    1. With the fingers, press the seal onto the valve stem past the indentation that houses the collets when the valve is installed.
    2. Insert the spring guide over the end of the valve stem and push down until the spring guide bottoms out.
  4. From the top of the cylinder head, fit the spring and spring retainer, as marked on removal, onto the valve stem.
  5. Push the spring down with the CTV spring remover and insert the collets into the spring retainer. Push until they lock into place.
  6. Install the piston and seal, as removed. Be careful not to damage the seal on installation. See Figure 41926 .
  7. From the bottom of the cylinder head, remove the spacer.
  8. From the top of the cylinder head, install a new O-ring on the end cover.
  9. Install the end cover.
  10. Install the injector nozzle. Refer to section .
  11. Install the cylinder head. Refer to section .
  12. Repeat this procedure for each constant-throttle valve.