CDR Valve Failure?

jaluhn83

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So I'm curious.... has anyone ever determined exactly what causes the CDR valve to "fail"? It's tribal knowledge to replace them to correct high oil consumption, but yet having taken them apart I can't see anything that would wear out. All they are is a can with a rubber diaphragm designed to close off the PCV system under conditions of high intake vacuum. Mainly as I understand it this is solely to prevent the engine from sucking down oil vapors and running away in the event of a clogged intake. I guess I can see the diaphragm getting old and not working right, but under normal operation there's no way you should get high enough vacuum for it to even become an issue.

Thoughts?
 

ZWilson07

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So I'm curious.... has anyone ever determined exactly what causes the CDR valve to "fail"? It's tribal knowledge to replace them to correct high oil consumption, but yet having taken them apart I can't see anything that would wear out. All they are is a can with a rubber diaphragm designed to close off the PCV system under conditions of high intake vacuum. Mainly as I understand it this is solely to prevent the engine from sucking down oil vapors and running away in the event of a clogged intake. I guess I can see the diaphragm getting old and not working right, but under normal operation there's no way you should get high enough vacuum for it to even become an issue.

Thoughts?


Mainly the problems that come from them "failing" is just them getting gunked up and clogged up which is why they are supposed to be seviced every other oil change or so. Which basically just is taking them off and soaking them and cleaning them and that just prevents build up and sludge from occuring inside.
 

bagpiperjosh

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I dont mean to highjack this thread, but what is a cdr valve and where is it? I searched on the forums and didnt find anything
 

jaluhn83

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CDR = Crankcase depression regulator. It's the can looking thing on the back of the intake right under the air filter housing. (assuming you have a stock na motor) It's sort of similar to the PCV system on a gasser - it allow gases and oil vapor from the crankcase to vent into the intake so they can be burnt off. Much less complicated than a gasser though cause you don't need to regulate vacuum.
 

idi_econoline

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Its nickname is the "tuna can," bagpiperjosh, as it resembles one. On the n/a engines, large hose comes up from the crankcase from valley pan, and the valve attaches to the intake with two small bolts.

Though this assembly's very easy to access for me (from inside) with my van, it is way-back-behind for you fellas with Fs.
 

Black dawg

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So I'm curious.... has anyone ever determined exactly what causes the CDR valve to "fail"? It's tribal knowledge to replace them to correct high oil consumption, but yet having taken them apart I can't see anything that would wear out. All they are is a can with a rubber diaphragm designed to close off the PCV system under conditions of high intake vacuum. Mainly as I understand it this is solely to prevent the engine from sucking down oil vapors and running away in the event of a clogged intake. I guess I can see the diaphragm getting old and not working right, but under normal operation there's no way you should get high enough vacuum for it to even become an issue.


At one point, I had the cdr hooked like stock, and another crankcase vent into the exhaust. Every once in awhile I would notice a fair amount of blowby coming out of the tailpipe. When I noticed it, I pulled the cdr, and it was stuck shut. I cleaned it a couple times with no improvement (intermittently sticking shut). replacement cured the problem. I guess what I am getting at is that under certain conditions the internals of the cdr are actually moving. This was with a clean air filter on a turbo motor
 

gdhillon

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How is it attached to the intake? Ive .never cleaned mine I think I should soon

Sorry about the thread jack
 

Matrix37495

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There are two bolts that hold it to the intake and either a rubber tube or a steel tube and grommet into the valley pan...
 

rbcorn2

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1989 7.3 - I need help (this seems to be the only string) with what I expect is the CDR.

I've pulled my air filter, cleaner housing etc and the is a !" hose coming from the back of the cleaner housing.

Where does this hose go? Thinking CDR but there is no junction for this hose....
 

Wyreth

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To the OP, you must remember that ANY moving part will ALWAYS fail eventually. If for no other reason than repetitive stress fatigue. Then take into account that the diaphragm in a CDR is a rubber compound that is then exposed to caustic blowby gasses, oil, and constant cycles of hot-cold. All of which accelerate oxidation.

That's how they fail.

1989 7.3 - I need help (this seems to be the only string) with what I expect is the CDR.

I've pulled my air filter, cleaner housing etc and the is a !" hose coming from the back of the cleaner housing.

Where does this hose go? Thinking CDR but there is no junction for this hose....

No, I don't know what the tube was ever suposed to attach to. If anything. But the CDR attaches to the valley pan, then to the intake manifold. Take off your air cleaner, the tuna can looking thinger behind the hole is your CDR. I have the same hose, and there simply isn't anything on my engine for it to attach to. I stopped wondering about it a while ago.
 

sassyrel

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i wonder...is it also called,,a vapor canister purge valve???? i tried to get the pic,,on rock auto,,and it wouldnt show......
 

Wyreth

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So where might one find a new CDR? Dealer only part?

Yes, it is a dealer only bit. This sight: https://www.silverstatefordparts.com has them for $47.12 before shipping. So that's another option if your local stealership tries to rob you.
P/N:E3TZ-6A665-A (from the parts bin thread here) They call it an "Adapter assembly for crankcase" or something silly like that.

i wonder...is it also called,,a vapor canister purge valve???? i tried to get the pic,,on rock auto,,and it wouldnt show......

No that's a different part. Actually I don't think our trucks even have a vapor canister. That's part of the smog gear on gassers.
 

RLDSL

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THe rubber diaphram will tear eventually causing failure and if the thing is gunked up it wont function. THey were supposed to be cleaned at each oil change but none ever were.

It's not an open close device, it is a crankcase depression REGULATOR . operative word *regulator* the thing does not just wait till a certain point and then shut off the breather, you would blow out all your seals instantly with the kind of blowby in these things, you would probably shoot them clean out of their seats. What it does is *regulate* the pressure in the crankcase at a constant slightly positive pressure, with the engine pulling on the other side to scavange the blowby gasses, if vacuum conditions get too high, it flutters shut to intermittantly *break* the vacuum to keep a constant suction from forming which could cause a siphon effect which can end up drawing all of the oil right out of your crankcase causing a runaway

THe early VW diesel engines had a preather top that didnt take these things into account and there were a number of runaways before they changed the breather top into one that included an oil separator . You have to have some way to prevent oil from mainlining straight into the intake, the CDR is that device, and you must keep it functioning properly.
 
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