Crank Case Evac System No Longer Working?

[6 Nebraska IDIs]

I have a crank case evac running into the exhaust stream in my moms 94 CC, the one with the "new 6.9", and it apparently is no longer working. It has so much blow by its insane in the first place. But I pulled the dip stick the other day when it was good and warm, smoke just plumed out of it, but when I revved the engine up above 1200 rpm it didnt dissipate at all.
The tube running to the check valve in the exhaust is attached to the CDR valve on the valve cover, Im guessing one of those valves has failed. And the CDR is brand new, less than 5k on it.
What do you guys think's wrong with it? Especially the ones running this system.

 

[david85]

If your crank case vent is routed to the exhaust, then there is no reason for the gasses to get pulled back in when you rev it up (quite the opposite). Aside from emissions, the big reason for the factory routing of the CDR to the intake was to control the blow by pressures from building up. Small amounts of vacuum that are in the intake manifold of the engine help to control this. No vacuum on the end of the crank case vent hose, then no real control of crank case pressure other than how quickly it can vent out by itself.

Crank case gasses that are routed to the exhaust also have to defeat more pressure because even the best flowing exhaust systems will have some pressure all the way to the end. By going from the intake manifold (mild vacuum) to the exhaust line (mild pressure), you are asking a lot for the crank case gasses to vent as well as they would with the factory configuration. I almost wonder if its possible for pressure from the tail pipe to be getting into the crank case.

Unless I've missed something.

 

[OLDBULL8]

X1 Specially with a turbo on it. More so if it has a muffler on it. The CDR has a rubber diaphram in it, maybe the hot exhaust gasses destroyed it.

 

[The Warden]

Actually, as I understand it, the crankcase-gas-into-exhaust design, if done properly, is supposed to create a venturi effect in the exhaust system...so it's at least supposed to create negative crankcase pressure.

Take a look at these two threads:

http://oilburners.net/forums/showthread.php?t=8888

http://oilburners.net/forums/showthread.php?t=20605

As to the OP...I would pull the CDR off and start the engine, and see if there's suction in the hose between the CDR and the exhaust pipe. If not, maybe there's soot build-up on the fitting in the exhaust, or if you're not using oil-rated hose, maybe the hose is collapsing? And, as you mentioned the valve at the exhaust end could be gone as well.

Just a few things to think about...good luck!!

 

[RLDSL]

Did you test the initial design of the system?
How was it behaving then as compared to now?
I don't see how a CDR would make a difference if it's going into an exhaust tube feed, I would think that you would have eliminated that thing as it is not needed to prevent a runaway with oil vapours bypassing the intake.
Did you check the nozzle where it joins the exhaust pipe to see if it has carboned up and clogged?
A line possibly kinked?

 

[Ironman03R]

Ditch the CDR. I had a similar setup and have has a bad rear seal leak for awhile. Also I didnt see as much "venting" out the tail pipe as I used to. I pulled the CDR apart and pulled out the diaphram and spring and modified the tube inside it to get more flow. It has slowed my oil leak down a lot and I notice the crankcase gasses out the tail pipe again. I'm thinking that theres so much vacuum on it that its pulling the cdr closed letting the pressure build up and over time it is either wearing the spring down or the diaphram is sticking closed causing it.

 

[sle2115]

Do you have a check valve installed?

 

[Black dawg]

do you have the exhaust hose hooked between the cdr and intake or just straight to the cdr and no more intake connection. for a long time i ran two crankcase vents , the normal cdr to intake, and a 5/8 hose into the exhaust with a check valve. quite often i would notice lots of blowby out the tailpipe and found that the cdr would stick closed forcing all the blowby out the exhaust. got rid of the cdr and no more problems. I dont know that running with no cdr is the best thing to do, but ive had some real worn out turbo 6.9s that had some real crazy blowby, with no cdr, and never had any runaway problems

 

[Dsl_Dog_Treat]

Sean, I'm wondering if the check valve at the exhaust has gummed up and stuck shut.
If there's a large smount of oil vapors hitting that, I'm wondering if the heat from the exhaust hasn't played a factor in the check valve failure.

Cause at an idle, 4" pipe doesn't draw much vacuum on the C/C's I've noticed.


This "new" 6.9, was it a rebuild or just a new to you engine?

I'm wondering if it's a fresh motor, that the rings aren't seating up properly with that type of blowby you are seeing.

 

[6 Nebraska IDIs]

Hey guys. We'll you've certainly given me some ideas to go by. The CDR valve was brand new when we installed this engine. To be honest it'd kinda **** me off if $60 just went down the drain like that but live and learn. It's been so cold here lately I dont want to go out and take the thing appart. Its possible that the check valve quit working, but I do have one there. When we first started running this engine it had literally a cloud of blow by that would roll out the exhaust even at idle. It's no longer doing this. The engine leaks oil so badly we've started putting oil from my dads work in it instead of the expensive stuff we run in all our other trucks. It just costs too much to keep that oil in there. We've replaced the front main seal 3 times and it keeps leaking from there.
The engine was supposedly JUST rebuilt when we got it, only had 5k on it. But this is the one that the idiot had left it outside and when we got it home realized that it wasnt oil in the crank case, but WATER. In fact it was completely full of water. We'd already hauled the thing home from Kansas City at that point and the guy refused to refund our money so we stuck with this engine. But to be honest Im so sick of it leaking oil, smelling bad, not starting in the morning, etc etc, that I've literally TRIED to burn the sucker to the ground twice. Pedal to the floor, up hill with a strong headwind. I've put it up to 1250* and 14.5lbs of boost and I cant get the thing to lift a head off. Beats me. Everything else about the engine is crap but it just wont blow up. About all it does is move the truck around and its not even good at doing that.
The exhaust is a banks system, and Im not sure if its 3.5 or 4" in diameter. Here I've got my own truck to work on, and this one keeps causing problems. Like my dad said, I probably shouldn't TRY blowing it up until I atleast get my truck fixed. But man if you had to deal with it, you'd try blowing it up too. lol

 

[Dsl_Dog_Treat]

Block on the pedal, with a garden hose shoved into the air cleaner and run like hell.

j/k

Being full of water, it sounds like a need to go thru it and freshen things up.
Them rings are prolly yer #1 culprit me thinks.

 

[dyoung14]

it keeps leaking oil? is it maybe blowing pressure back up into it since that thing is routed into the exaust?, why not put the cdr back the way its supose to be stock and run it into the intake side of the turbo, instead of trying to put it into the exaust, that way you know that it is venting. then go from there, but after i heard about water being in the bottom end that kinda scares me

 

[Ironman03R]

No I dont have a check valve. Heres what I did on mine:

 

[david85]

I know this isn't a popular view here, but I still think that the original CDR position and routing to the intake from factory was the best setup. Since the rebuild, my truck hasn't leaked a single drop of oil.

Having said that, you could try to route an RDT temporarily to an open container under the hood (or strait to the road if you prefer) and see if it still ****** oil. It really sounds to me like the pressure from the tailpipe is getting forced back up the tube and into the crank case where it then pops the seals. Popping off the tube at the exhaust end would rule that in or out as a possible cause.

Wouldn't be hard to do so I think its worth a try when you get some time.