CDR

[David Brady]

Has anyone replaced the CDR with a non-dealer part? My local parts house has a cheaper one made by "Standard" that I'm going to try. I have been noticing more leaks and weeps and when I checked the CDR it wasn't pulling any vacuum at all.

[ucdavis]

Guess I need to add this to my list of abbreviations. What's a CDR?
Thanks

[David Brady]

Sorry, thats the crankcase depression regulator on the valve cover. It performs the same function I believe as the PCV on the gassers but we can't call it the same thing, because diesels are better, I guess.

[britannic]

Since a malfunctioning CDR can cause crankshaft seal leaks or allow enough oil vapor to actually power surge the engine with the throttle closed, I would recommend a GM part.

Prices range from $17.00-39.00 over at www.gmpartsdirect.com (http://www.gmpartsdirect.com) depending on your model year etc.

Your existing CDR can be cleaned out, but be aware that the diaphragm can fail if solvents are used.

[David Brady]

Brittanic,
The power surging from vapors would be when it opens and dumps a good volume in all at once? Because I am seeing leaks it looks like at the front main and maybe the rear main and the valve covers and oilpan. My dealer wants $75 and autopts wants $55. Is it possible that standard makes these for GM(always a hope for cheapskates like myself).

[gmctd]

The CDR is fully open at idle, and will start closing as compressor inlet vacuum reaches setpoint determined by the CDR spring.
Inlet vacuum is determined by engine rpm and loading, and air filter restriction.
Failure (diaphragm rupture) results in excessive oil consumption, where the compressor intake is drawing oil thru the valve cover.
The CDR rarely fails in the closed position - the internal regulator spring keeps the valve fully open. If the diaphragm ruptures, vacuum cannot regulate the valve closed.

jd

[StephenA]

Anyone know if the 92 6.5 has a CDR? Looks like the OBD1 computer is only for the ABS brakes & auto tranny, and doesn't track the engine at all... So many fo the sensors on later models are not necessary. Do I have a CDR?
P.S. Adding CDR to TDP Glossary.

[David Brady]

JD,
I checked my CDR at idle by the tube off the dipstick into the liquid method, but had no vacuum. Now my new CDR I installed last night tested the same way. Is there some other possible leak in the system or will the vacuum be so light at idle that this won't work? The new CDR looks identical to the one I took off with the AC stamp and part no.s and sticker. :confused:

[number two]

StephenA-my '93 has a CDR. It's on the right side rocker cover-installs into a rubber grommet like a PCVvalve and has a hose going over to the turbo. Can't miss it.

[StephenA]

Thanks numbertwo! -so that's what that big brass looking can is... -wonder how you test it?
Now if I could just find my lift pump relay- GM says it's s'posed to be on the driverside sidewall, but it ain't!
I mean -nowhere -nohow -nothin'!!! :mad:
How do you replace something you can't find?
-Stephen

[LanduytG]

The CDR is what is used to control the crankcase pressure. In the old days before EPA we had blow by tubes running down toward the ground. Well we can't do that any more so we now suck the crankcase gases into the intake so they can be burned. If we suck the gases out without regulation you could have a run away engine if you were to break a ring or if the engine had enough wear to have a lot of blow by. The CDR limits the amount of vacuum to about 4" of water vacuum. This is enough vacuum to keep everything happy and still maintain a bit of safety. You could still have a run away but certainly not as bad. This is how you test the CDR, pull the dip stick out and put a piece of 3/8" ID tubing over it. Hook up the other end to a u tube manometer. You can make one out of the same tube by making a u in the tube and fill the u with color water. Use food coloring so you can see it a little easier. Now rev the engine, when you do the water in the u tube will move toward the dip stick tube. If it sucks it out the CDR is not working. But if it moves and just holds its postion then the CDR is OK. I hope I have made this clear as mud ;) I have some pictures of what I use.


This is what I use. You can see that I have it so it will plug into the dip stick tube on the VW TDI.
http://images.mmcorp.net/members/LanduytG/cc3.jpg

Here you can see when I first rev the engine that it will peg the needle.

http://images.mmcorp.net/members/LanduytG/cc4.jpg

After the CCV as its called on the VW takes hold it puls it back to 1" of water vacuum.
http://images.mmcorp.net/members/LanduytG/cc5.jpg

[David Brady]

Thanks Greg, I think now I need to rev the engine while testing this. I thought about it earlier but it's not as easy with this electronic controlled pump. 4" of water ought to pull in my weeps, I'll give it a good cleaning this weekend.

[StephenA]

Golly Greg, That's quite an explanation! Thanks! This will make it very easy to check my CDR.
Say, how much are your Amsoil 6.5 foam filters?
Stephen

[britannic]

JDave: my CDR failed and caused the engine to surge when coasting at 2500rpm or more; a real issue when descending hills. It wasn't consistent or subtle, but really agressive as if I was hitting the throttle.

It turns out oil was building up in the intake manifold and the higher rpms would create enough suction to draw it all in and burn it. I got a new GM CDR from www.gmpartsdirect.com (http://www.gmpartsdirect.com) for $17.00 + shipping for my CUCV, other models use different outlets (valve cover etc.) and thus have separate part numbers and for some reason are more expensive.

[got boost?]

So if my understanding of all that has been said is correct, excessive oil on the compresser side of the turbo can be caused by a malfunctioning CDR? I also have noticed a small amount of oil weeping from the rear main seal.

If this is true, I am relieved because I was concerned that I might have something like a broken compression ring that was causing some excessive crankcase pressure.

[britannic]

got boost?: your understanding is correct, the CDR will definitely cause the symptoms you described.

[gmctd]

Oil at the compressor inlet is normal for a functional CDR.
Excessive oil consumption can be result of non-functional CDR.
Controlling excessive blow-by from worn piston rings is not a function of CDR.

Leak at front OR rear main seal is normal for functional CDR.
Why?
Leak at rear only, or front only, or even both, is normal for functional CDR, where crankshaft seal(s) have actually failed.

The CDR functions to limit crankcase vacuum to 4" to 6" on the water column.
27" of water = 1psi
2" mercury = 1psi

Early years CDR main failure was from rust, where the flow path was thru external breather cap. Result - no regulation.
Rube Goldberg arrangement of tubing and hoses was source of failure for the middle years engines.

The passenger-side valve cover mounting was the ultimate configuration, requiring only one external hose, proving most reliable.

jd

[LanduytG]

If one didn't want oil to get to the turbo just use a Racor CCV4500 or smaller unit. This will regulate crankcase pressure and catch any excess oil.

Greg

[David Brady]

Greg,
Would I be able to catch this oil and put it back in the pan somehow and reduce consumption? What does this do or how does the CCV4500 work? Thanks,

[triggerman]

If the motor oil you are useing is not "CI" rated , you might want to try it. This new Diesel oil rateing is supposed to keep the oil fumes to a minimum. By 07 nearly all new big rig Diesels will be equipted with EGR systems of one sort or another. CDR oil fumes and EGR gases together, clog intake manifolds. I was useing Castrol syntec blend and found it to fume terribly "not CI". Went to Pennsoil Long Life CI rated and now the collection pipe I made up only has water in it. The turbo inlet pipe has NO oil pooling in the rubber ribes. I used to use Shell Rotela but the stuff would foam up so bad in my generator, I'd loose oil pressure and the murffy switch would shut it down. For a bean oil, Pennsoil looks like its doeing OK. :cool:

[got boost?]

Greg,

I looked at Racor's site and couldn't find the CCV4500 you reffered to. Can you help? Do you feel this modification is worth it?

[LanduytG]

Got Boost

Here is a link (http://www.parker.com/parkersql/default.asp?type=2&id=27) to the CCV's. I think Racor is make smaller ones now as well. If your CDR is bad this is a good option.

Greg