MBE 900 – Section 1.3 Engine Brake

Section 1.3
Engine Brake

The constant throttle valves are small valves which are built into the cylinder head. When the engine brake is switched on, the constant-throttle valves are put under pressure, which in turn opens the valves. On the 6-cylinder model, the constant throttles are activated by engine oil pressure. On 4-cylinder engines, the constant throttles are activated by vehicle air pressure. The engine brake is activated by the DDEC-VCU.‪

Section 1.3.1
Constant-Throttle Valve Removal

Remove the constant-throttle valve as follows:‪

1. Remove the cylinder head. Refer to "1.1.1 Cylinder Head Cover Removal" .

   NOTICE:
   Do not place the head mating surface down on a flat surface. This would damage the injection nozzles, which protrude slightly.‪

2. Remove the nozzle holder. For detailed procedures, refer to "2.3.1 Nozzle Holder Removal" .
3. From the top of the cylinder head, remove the constant throttle valve end cover. See Figure "Constant-Throttle Valve (exploded view)" .
   

   1. End Cover‪	6. Spring Retainer‪
   2. O-ring‪	7. Spring‪
   3. Seal‪	8. Spring Guide‪
   4. Piston‪	9. Valve‪
   5. Collet‪

   Figure 1. 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.

4. From the bottom of the cylinder head, insert a suitable spacer about 5.3 mm (7/32 in.) in height. See Figure "Constant-Throttle Valve (cutaway view, with spacer installed)" .
   

   1. End Cover‪	6. Spring Retainer‪
   2. O-ring‪	7. Spring‪
   3. Seal‪	8. Spring Guide‪
   4. Piston‪	9. Valve‪
   5. Collet‪	10. Spacer [5.3 mm (0.21 in.)]‪

   Figure 2. Constant-Throttle Valve (cutaway view, with spacer installed)

5. From the top of the cylinder head, insert the constant-throttle valve (CTV) piston remover J-46400 into the valve bore until it contacts the piston. Pull the piston out of the valve bore. See Figure "Removing the Piston" .
   

   1. Seal‪

   2. Piston‪

   Figure 3. Removing the Piston

6. Inspect the seal around the piston for damage and signs of wear. If necessary, replace the piston and seal.
7. Insert the CTV spring remover J-46401 down onto the spring retainer. Remove the collets with a magnetic pin. See Figure "Compressing the Spring" .
   

   1. Magnetic Pin‪	3. Spring Retainer‪
   2. Collet‪	4. Spring‪

   Figure 4. Compressing the Spring

8. Relieve the pressure on the spring. Remove the spring retainer, spring and spring guide. For ease of installation, mark the location of the spring retainer and spring guide with a paint pen.
9. From the bottom of the cylinder head, draw out the valve and spacer. For ease of installation, mark the location of the valve with a paint pen.
10. Do the same procedure for each valve.

Section 1.3.2
Constant-Throttle Valves Installation

Install constant-throttle valves as follows:‪

1. Lubricate the valve stem with a light coating of engine oil. From the bottom of the cylinder head, push the valve, as marked on removal, into the valve bore. See Figure "Constant-Throttle Valve (exploded view)" .

   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 5.3 mm (7/32 in.) in height. See Figure "Constant-Throttle Valve (cutaway view, with spacer installed)" .
3. From the top of the cylinder head, fit the spring guide, spring, and spring retainer, as marked on removal, onto the valve stem.
4. Push the spring down with the CTV spring remover J-46401 and insert the collets into the spring retainer. Push until they lock into place.
5. Install the piston and seal, as removed. Be careful not to damage the seal on installation. See Figure "Removing the Piston" .
6. Remove the spacer from the bottom of the cylinder head.
7. Install a new O-ring on the end cover.
8. Install the end cover.
9. Install the nozzle holder. For detailed procedures, refer to "2.3.2 Nozzle Holder Installation" .
10. Install the cylinder head. For detailed procedures, refer to "1.2.2 Cylinder Head Installation" .
11. Perform the same procedure for each valve, as required.