Function of the CDR Valve

• On some diesel engines, vacuum is required to actively pull fumes from the crankcase, thus the CRD provides this positive vacuum by running a hose from the CRD valve into a pre-turbo location on the air intake. By routing crankcase vapor back into the intake tract, emissions and black smoke are reduced during vehicle operation.
  
  

CDR Issues

• It is common for the CDR connection tube to develop a tear or rip over time. When this happens, the crankcase vapors will vent into the engine bay. If a replacement CDR connection tube is not immediately available, a section of radiator hose or liberal use of duct tape can be used to effect a temporary repair.
  
  

Effects of a Failed CDR Vent

• A failed CDR valve or torn CDR connection tube will result in black oily crankcase vapors venting into the engine bay, which will reek of diesel fuel, and become coated in oily residue. As the CDR valve is an emissions sub-system, it will not affect overall operation of a 6.9 liter diesel engine.