Two engine brake packages are offered on the engine: the Konstrandrossel (KD brake) with exhaust brake and a D-brake with exhaust brake. Both the KD brake and D-brake use a decompression valve in each cylinder head. The Konstrandrossel or "constant throttle" holds the decompression valve open continuously while braking. The decompression valves are pneumatically actuated through a connection to the vehicle air brake supply tank.
The D-brake provides increased braking performance by opening the decompression valves for a short time from just before TDC to about 90 to 120 after TDC. A hydraulic pump driven from the front gear train actuates the decompression valves in the D-brake system. Oil is directed from the hydraulic pump in engine firing order sequence. See Figure 25731 .
DVB Hydraulic Pump
Determine if repair or replacement of DVB hydraulic pump is necessary. See Figure 25744 .
Repair or Replacement of DVB Hydraulic Pump Flowchart
Pre-cleaning is not necessary.
Note: The hydraulic pump is timed to the engine gear train. Before disassembly, mark each of the six supply lines for proper reassembly. The timing order of the hydraulic pump is the same as the engine firing order.
Remove the DVB hydraulic pump as follows:
Inspect the DVB hydraulic pump components as follows:
Install the DVB hydraulic pump as follows ( see Figure 25635 ):
1.DVB Pump Assembly
3.Camshaft DVB Pump Drive Gear
DVB Hydraulic Pump Installation
Note: Ensure that the No. 1 cylinder is at TDC prior to installing the hydraulic pump.
Note: The location of the camshaft DVB drive gear. If the crankshaft is properly positioned, the timing marks will be visible on the drive gear through the inspection hole in the upper front cover.
Note: Slight rocking of the pump may be required to align the hydraulic pump drive gear to the engine gear train.