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CDR valve?

G

great white

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So, my 6.5 has a fair bit of blowby. It also has a fair bit of oil in the bloody intake/turbo.

I've done the water test before and if I recall it pushes the water down about 1/8-1/4 inch at idle but pulls it up about 4-6 inches at 2000. IIRC, that's too much vacuum at 2000 rpm, which indicates a bad CDR.

I'm about to go out to do a redo the "water check" to confirm what I remember.

I'm thinking the CDR is pooched in addition to a.......ahem...... "well seasoned" engine.

Couple Q's:

1. Anyone think a new CDR may lessen the oil in the intake? (I doubt anything will eliminate it)

2. I know the purpose of a CDR is to limit the vacuum at higher RPM's in a turbo diesel. But, how is it constructed internally? (IE: butyl rubber diaphragm and spring, shuttle valve, etc). Or, what fails inside a CDR if that's a better question....

3. Any point in trying to clean it? I think I've read soaking overnight in diesel or kero sometimes cleans a sticking CDR. Although, mine seems to be so soaked in fresh (well, sooty black) oil, I'm leaning more towards a failure than "gunked up".

4. Or, am I just experiencing the symptoms of a worn engine and the cdr just can't cope with it?

Just looking for some good input before I order one and plunk down a 100 or so bucks.....
 
1. Yes. Properly functioning CDR can reduce oil in the intake. IMO, the truck runs better.
2. Some sort of diaphragm. IIRC, you clean with gasoline.
3. IIRC, you clean with gasoline. No guarantee it will work after that.
4. Not sure.

In the US, the CDR cost less than $50. Last time I got it at Napaonline.
The part store call it PCV. (from the Technical Library).

Some people said it is a maintenance item.
 
I changed mine a few months back just cause it looked like original OEM with 200K on my clock. If iirc it was about $50 bucs at local carquest.

I installed my original CDR that I pulled off mine on my neighbors 91 6.2, should have seen what his looked like OEM with 278K on his clock...my OEM original looked 100X better then his old one.

I was gonna cut his old one open to see what is in there, but he wanted to keep it...so I'll be interested in the replies here.

Mine does seem to have slowed down a little on oil consumption after I changed it...but my consumption was never more then 1qt in 2500 miles to begin with. I don't think that amount of oil used between changes at 212K is too bad IMO
 
The truck doesnt really make a lot of vacuum when in park and revving, obvioulsy some, but not nearly enough to close the CDR. The vacuum it closes under is that of the boost. Unless you go get a CDR from a N/A truck, which I have read is different. So I have never thought that water test is valid, just proves its not stuck closed. But whats still possible is that its stuck open and doesnt close under 10psi of boost and there is loads of vacuum in the crankcase now that the CDR was supposed to prevent.

I think its supposed to close around the vacuum created at 6psi of boost at RPMs accelerating or sustained load uphill or something like that.

I get loads of blowby too, and oil in the intake, but I decided to put the CDR on top of the oil fill tube instead, because I didnt like it sucking oil out the valve cover.
 
I've only read that they are different, never verified or tested it. Looking at parts seems like they only offer one type. It was gmctd I believe that mentioned there were different ones.
 
my interest is defineately piqued here. we need a mod for this POS. here's pics of an old one I disassembled. last one is with it cleaned up I used brake clean and the rubber didn't soften one bit. (unlike rumors I've heard)
 

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Which way does it operate, if you could draw like annotations on the pictures on how the inside works, which way the spring pushes on or vacuum pulls.
 
oh BTW the diaphram as many call it is simply a centering/holding device for the metal flapper. not much to fail
 
If spring holds it open, and you said it was rather stiff, then wouldnt we need a lot of vacuum to pull it closed? Or when you said we only need a little vacuum were you referring to we really only want a little vacuum in the crankcase? Does crankcase pressure help close the spring or help hold it open?

You can open pictures in Microsoft Paint and there is a text box button and buttons to draw lines and such.
 
Also I would think it depends on how clean your air filter is as to how much vacuum will build during the water test???. An old air filter will increase draw on an engine wouldn't it./?
 
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buddy said:
If spring holds it open, and you said it was rather stiff, then wouldnt we need a lot of vacuum to pull it closed? Or when you said we only need a little vacuum were you referring to we really only want a little vacuum in the crankcase? Does crankcase pressure help close the spring or help hold it open?

You can open pictures in Microsoft Paint and there is a text box button and buttons to draw lines and such.
Click to expand...
 
I'm wondering about adding an adjustable spring to the topside of valve so one could reduce the travel needed (currently approx 1/2") and at the same time lessen the spring pressure from the bottom side.
 
there is a pinhole on the closed side,sometimes it is plugged,rendering it useless.
they are easy to test.

Take the CDR off the engine
1) hold the valve cover tube closed
2) suck hard on the turbo tube,you should feel the diaphram close.If not,the Thing is toast(crack or hole in the diaphram)
3) put a finger on the pinhole,keep it there.
4) release both tube openings

if the diaprham holds in closed position with the pinhole plugged and opens after pinhole is open ,the thing works just fine.


GW,you may have to much blow by on that old boat,even a new CDR cant handle that,look in my sig for solutions. The 95 version is the better one,cheaper too.
 
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