CDR and blowby

[Cowracer]

Ok, guys. I read every post I can on Blowby and the function of the CDR, and I still dont fully understand its operation.

My truck (which runs as good as can be expected on the original injectors at 180K miles) suffers from massive blowby. The dipstick and oil filler vents a LOT oily mist at all times when the engine runs, even at idle.

So I think to myself that the CDR is faulty. Just to check, I pull the tube out of the turbo inlet, and it is SPEWING smoke. Imagine a vapor humidifer. Now imagine the vapor output heavier than that. Now a little more still. There, thats about how much vapor/mist/smoke the CDR is dumping into my turbo. I assume that if the CDR is venting into the turbo, it is working OK? is this correct? I did not try GMCTD's manometer test simply because it would have blown all the water out of the manomenter tubes rather than sucking it up to a level with vacuum.

My oil consuption has gotten quite a bit worse in the last few weeks. The truck does not surge due to burning its own oil, and it doesn't leak liquid oil out of any seals.

If it was a gasser, I would expect that the rings are shot. Would you guess this is the case with a diesel? I guess a compression check would tell for sure.

Tim

[john8662]

Bad blow-by, signs of worn piston rings, etc. I doubt that its the CDR valve. Usually a CDR failure results in leaking oil out the front and rear main seals, and other places oil can leak, due to excessive presure in the crankcase. Sounds like you'll need to run a compression test to know for sure what the deal is.

[JohnC]

When the engine is operating correctly, there is a vacuum generated by the air flowing through the intake into the turbo inlet. This vacuum is applied to the crankcase to deal with crankcase vapors and help prevent oil leakage past the seals. The intake is capable of generating more vacuum than is appropriate, and if left unregualted would cause air to be drawn past the oil seals and introduce foreign matter into the crankcase/oil. The CDR limits that vacuum to a reasonable level. When the CDR fails it can apply too much vacuum to the crankcase and draw oil vapor that would ordinarily condense back into the sump into the intake.

When an engine is generating a lot of blowby, then there's no chance of too much crankcase vacuum and the CDR passes all that vapor into the inlet, preventing crankcase pressurization. The CDR cannot cause the blowby, however, which sounds like your issue.

[tom.mcinerney]

I can't add to what J.C. and GMCTD describe about CDR (i don't have a feel for the beast).

Some TDP members have run with the CDR output disconnected, or at least a valve cover venting to atmos. How are the dipstick/oil filler with the CDR disconnested??

It's quite possible ring/blowby is culprit. Given mileage and other previous commentary by driver, however, I tend toward guessing that either lifter(s) or head gasket leak(s) might be origin/contributor of/to problem. If a lifter malfunctions the cyl won't breathe properly. If head gasket leaks, can pressurize both waterjacket and crankcase. Of course if the head cracks contact the coolant, that's another prob.
[good luck]!

[eracers999]

If the engine still runs good then run it. You could do it a favor and rout that stinky blo by tube somwhere the heat and a/c wont pick it up in to the atmosphere. As far as oil in the intake goes the cdr was never designed to handle 2 to 3 times the vaccume levels generated by the performance chips and boost ehancers that most of us have installed. I can only imagine the carbon build up from running the crankcase oil into the intake and then burning it. My personal opinion, the cdr being hooked to the intake tube is a birth defect. Once i seen oil in the intake manifold and i knew it wasnt coming from the turbo that was definatly going to change. I have run mine vented for quite somtime, i dont have any more or less leaks and my oil milage has increased. Thats on a 45k motor. I work on series 60's detroits, N14s, M11, L10's. The detroits and the m11 l10s blo by can get pretty bad. They run just fine and dont have a problem going the distance till engine swing.
The real question should be 1. What is crankcase pressure with cdr vented. 2. What is crankcase pressue with the cdr hooked up to intake tube.
Kent

[jspringator]

Mine has developed a rythmic click, which I believed was a failed tuna can. Does it click when it fails?