Gunther
First, you need to know the function of the CDR. It is called a "crankcase depression regulator". What that means is that it is supposed to "regulate" the low pressure within the crankcase.
Truth be told, it doesn't do anything at all. Inside the thing there is only a weak spring, and a large rubber diaphram. The only thing anyone has so far been able to determine that it actually "might" do is that if somehow the intake got majorly restricted then the diaphram would be sucked shut by the high vacuum in the intake and prevent the engine from inhaling it's own crankcase oil. I personally doubt it can even do that, but that seem to be the only reason for the diaphram.
The thing is mounted on the back of the intake, and connects to the lifter area via a grommet on the valley pan. Any blow-by your engine has gets directed up through the CDR into the intake to be re-burned. Just by the fact that the thing has oily vapours passing through it, it will get some condensation of oil in it. It has no major function to condense oil though.(Way too small, no surface area etc)
When your engine starts to show high amounts of wear, valves/rings especially) then there will be high amounts of blow-by which contains large amounts of suspended oil vapour, which then is burned in the cylinders when it is directed into the intake.
That is the most likely reason for your oil consumption.
So, the answer is no. The CDR is not responsible.
It supposedly can however become somewhat plugged. If this happens you then have no path for the blow-by to return to the intake, and you can get the oily smell. The blow-by will find the path of least resistance out of the engine. Likely spots are around the dipstick tube, valve cover gaskets front and rear main seals, and oil leaks will be much more evident as pressure builds up in the crank area.
Some guys just buy a new CDR(around $50) Others make an effort to clean the thing. (rinse with varsol etc and drain)
Have a look in the intake. Is it all oily in there? If so, your engine is probably starting to show it's age, and oil consumption will just become worse. Price of oil is cheap though compared to a rebuild. These old diesels have a well known reputation for consumption of oil!!
Lastly, here is a couple pics of the inside of a CDR just for info....
..conceptual drawing..
..Pic 1..
..pic 2..
My old 6.9 uses a quart of oil for every 300 miles now It' been built and rebuilt. I'm just gonna continue to pour oil in it and drive it!!
Good luck with it...
Zigg
At least you can do away with your CDR and get a feel for what is really being passed out of the crankcase.
