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Discussion Starter #1 (Edited)
Since this question(s) has/have been asked a number of times in many places, I thought that I'd put together a post to discuss the things that I've learned from reviewing the threads I've seen over the past couple of years. This will hopefully condense the info and save others - especially newbies - from having to reinvent the wheel and do all the research themselves...

First, lets identify the two 'breather' pipe locations where an OCC could be installed:



(A) The braided hose that attaches to the *mid-point* of the valve cover and terminates on the top of the cold air intake at the, easily broken, plastic nipple of a stock LNF air intake.
(B) The braided hose that attaches to the *front* of the valve cover and terminates at the metal bracket, down directly in front of the turbo.

Now, the LNF engine is designed by GM not to require an external OCC. So let's first discuss why not... Hose (A) is there to allow cold air INTO the top of the engine. There is a one-way plastic check valve at the end of the hose on the CAI nipple that only allows air into the valve cover and blocks air and oil vapor from getting out of the engine into the air intake. Thus, with a working valve, there's no need for an OCC as there won't be any oily air flow.

On the other hand, hose (B) is there to allow/pull air-flow OUT of the top of the engine. In this case however, to avoid oil vapor getting ingested into the turbo and burned in the cylinders, the valve cover contains a set of internal baffles designed to condense out any oil vapor in the air and thus keep it in the top of the engine. This effectively forms an internal OCC and thus should not require an external OCC.

OKAY, so far so good. So then why would anyone install an OCC? The argument for putting an OCC in path (A) is that the the one-way check valve could malfunction and stick open, thus allowing oil into the cylinders. Thus an OCC in this position acts as insurance against that happening. [Note: Some folks have put an OCC in here and then also removed the check valve. DDM Dave has written that removing the valve can lead to weird noises (bad breathing?) from the engine and is not recommended. Apologies, Dave, if I've misquoted :)] UPDATE: Per GSStage1, old gummy oil can accumulate in the check valve and stick it open. Probably a good idea to clean the valve out occasionally with MAF cleaner, or similar, to protect against this.

The argument for putting an OCC in path (B) is that maybe the internal baffling does not do a good enough job and so an OCC would be a backup to capture any remaining oil vapor coming through that path. By the way, IIRC, path (B) is where DDM recommends installing their catch can.

Couple of closing points... oil vapor in the cylinder is BAD. It causes premature/uncontrolled detonation (knock) which can destroy your pistons/rings/cylinders. By all means add an OCC (or two) if you're scared of this. Secondly, any OCC you add will NOT protect against two other possible paths for oil getting into the cylinders: past worn piston rings; and more importantly, via worn turbo bearings.
 

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Discussion Starter #2 (Edited)
My opinion as an addendum to the above (but in a separate post so as not to dilute the summary)...

Personally, I don't think an OCC is warranted (but that's just my opinion and worth only the money you've paid for it!) I am a little wary of the check valve failure scenario, and to that end I propose to add a simple clear plastic fuel filter in-line with hose (A) on my car. Then if I ever see any oil residue in that filter I know that my valve has failed and so needs replacing. I'm prepared to let the internal baffling deal with oil vapor in the other path (B).

UPDATE: (again) Per GSStage1, a theory is that old gummy oil can accumulate in the check valve and cause it to stick open. Makes a lot of sense to me. Worth cleaning the valve out periodically.
 

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So, a year ago, I had oil all over and in my turbo. I took it to the dealer, they checked with GM, and the answer is that this is normal operation. The PCV and everything else was working properly. While this may be normal, I do not think it is good. And DDM found that oil going into the turbo would settle out into the I/C. Again, this may be normal but I do not think it is good. Hence, I bought and installed a DDM OCC.

That said, will my car go KABOOM without it? Probably not.
 

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WOW! I'm impressed TS. I was a little skeptical when I saw the title because there's very few people that understand this little system, but you were dead on except for one tiny little detail. The "PCV" valve is in the intake manifold. You can only see it or replace it if you pull the manifold off. The check valve in the middle VC line is simply that, just a check valve. It's not the PCV valve.

Here's my thoughts and experiences...
The check valve doesn't always hold the oil back as it's supposed to. That's where you get a lot of the oil in the intake in front of the turbo. The baffled port at the front of the valve cover works pretty good actually, some oil gets through and into the intake, but not much. I have a catch can on the middle line, after the check valve. Absolutely NO oil in the intake at the turbo, and if I'm running it hard I will get oil out of the catch can drain.

The other thing people don't realize is the ports on the intake are set up in a certain way. The middle line port, the one that's in the intake tube right before the turbo, is pointed INTO the flow of air, to try to create some amount of high pressure. The line that comes off the front vc port and goes into the turbo is plumbed into a spot in the compressor housing that gets the most amount of vacuum, even during max boost. That way that line has a somewhat low pressure or vacuum on it.

Here's the problem, when guys put on a bigger or different turbo, they route both of those lines to some ports welded onto the intake in front of the turbo. On a lot of aftermarket setups, those tubes for the pcv lines aren't pointed into or away from the airflow like they should be. Make sure when you guys are rebuilding or redesigning your intakes that you keep the flow going the same direction.

Another fwiw, just because GM didn't put a catch can or better baffling on these motors doesn't mean they didn't need it. The 3.6 V6's are having huge oil issues because of this kind of thing. You can pull the hose off the throttle body on one of those and literally pour oil out of it. If the catch cans guys are putting on are done right, there's really no downsides to it and it will probably help keep the valves a little cleaner.

Again, good post TS, and smart move on the post directing to this forum on the other forum. Good idea.
 

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Discussion Starter #5 (Edited)
Thanks GMTech! I appreciate the PCV correction and have changed the OP accordingly.

Very interesting point on the direction of air flow. Obviously the way the valve and baffles are set up indicate what direction the flow should be, but I hadn't thought about how that flow is actually instigated. I wonder if the aftermarket CAI's that folks have installed direct the air as you describe, or if they are simple 90 degree ports off the side(?)
 

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WOW! I'm impressed TS. I was a little skeptical when I saw the title because there's very few people that understand this little system, but you were dead on except for one tiny little detail. The "PCV" valve is in the intake manifold. You can only see it or replace it if you pull the manifold off. The check valve in the middle VC line is simply that, just a check valve. It's not the PCV valve.

Here's my thoughts and experiences...
The check valve doesn't always hold the oil back as it's supposed to. That's where you get a lot of the oil in the intake in front of the turbo. The baffled port at the front of the valve cover works pretty good actually, some oil gets through and into the intake, but not much. I have a catch can on the middle line, after the check valve. Absolutely NO oil in the intake at the turbo, and if I'm running it hard I will get oil out of the catch can drain.

The other thing people don't realize is the ports on the intake are set up in a certain way. The middle line port, the one that's in the intake tube right before the turbo, is pointed INTO the flow of air, to try to create some amount of high pressure. The line that comes off the front vc port and goes into the turbo is plumbed into a spot in the compressor housing that gets the most amount of vacuum, even during max boost. That way that line has a somewhat low pressure or vacuum on it.

Here's the problem, when guys put on a bigger or different turbo, they route both of those lines to some ports welded onto the intake in front of the turbo. On a lot of aftermarket setups, those tubes for the pcv lines aren't pointed into or away from the airflow like they should be. Make sure when you guys are rebuilding or redesigning your intakes that you keep the flow going the same direction.

Another fwiw, just because GM didn't put a catch can or better baffling on these motors doesn't mean they didn't need it. The 3.6 V6's are having huge oil issues because of this kind of thing. You can pull the hose off the throttle body on one of those and literally pour oil out of it. If the catch cans guys are putting on are done right, there's really no downsides to it and it will probably help keep the valves a little cleaner.

Again, good post TS, and smart move on the post directing to this forum on the other forum. Good idea.
So now comes the old question being, where should the OCC be installed, on the front line as recommended by DDM or the on the middle line?
 

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So now comes the old question being, where should the OCC be installed, on the front line as recommended by DDM or the on the middle line?
What, aside from engine bay space, would be the problem with multiple cans?

I still feel a little fuzzy without actually looking at a diagram or at the engine and being able to see all the lines discussed in these threads... :banghead:

...but really... if there is enough question to debate which line to use a OCC on, why not figure out a solution that covers all the bases? :thumbs:
 

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I'm glad TS and GM tech are here. Last weekend I installed an OCC but have yet to plumb it. I read DDM's data on where they suggest the cut in should be, but I was wary this was right. I see TS's note above on, essentially, the merits of both locations. So I'm probably more puzzled now than before. BTW, this action was prompted by the recent change out of my IC and pipes. The (old) pipe leading from the turbo was coated in oil while the pipe leading to the TB had traces of oil, but nothing I could coat my finger with.

I tried to post pics of the mounting but for whatever reason, this forum does not permit them :cuss:, so if anyone is interested, I will post them back over in my neck of the woods (SkyForum). The install was simple, out of the way, and took about 10 minutes tops. I assume that the actual plumbing will take a lot more time and effort.
 

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Discussion Starter #9
I'm glad TS and GM tech are here. Last weekend I installed an OCC but have yet to plumb it. I read DDM's data on where they suggest the cut in should be, but I was wary this was right. I see TS's note above on, essentially, the merits of both locations. So I'm probably more puzzled now than before. BTW, this action was prompted by the recent change out of my IC and pipes. The (old) pipe leading from the turbo was coated in oil while the pipe leading to the TB had traces of oil, but nothing I could coat my finger with.
That means your IC is probably acting as an OCC and is awash with oil :willy:

I would suggest you remove both pipes from the valve cover and see which has oil in it. The pipe (A) in my description is easy to remove if you're careful. Just release the white plastic lever/clip on the check valve at the air-filter intake end and pull it off (be careful not to put any sideways force on it - don't want to break that %^**&# nipple off!). Pipe (B) is more difficult. Easiest place is at the turbo end of the pipe. Undo the bolt and pull the bracket & pipe end off the turbo. Note: it's VERY tight and has a o-ring seal in it. Careful not to damage the seal when you pull the bracket or you'll need to replace it.

Good luck and post back with what you find.
 

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I'm new so def don't know much about how these cars are setup but would adding a secondary check valve in the center valve cover line be cheap insurance against the factory failing?
 

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That means your IC is probably acting as an OCC and is awash with oil :willy:

I would suggest you remove both pipes from the valve cover and see which has oil in it. The pipe (A) in my description is easy to remove if you're careful. Just release the white plastic lever/clip on the check valve at the air-filter intake end and pull it off (be careful not to put any sideways force on it - don't want to break that %^**&# nipple off!). Pipe (B) is more difficult. Easiest place is at the turbo end of the pipe. Undo the bolt and pull the bracket & pipe end off the turbo. Note: it's VERY tight and has a o-ring seal in it. Careful not to damage the seal when you pull the bracket or you'll need to replace it.

Good luck and post back with what you find.
TS: How in the Hell do I take the PCV Check valve (A) off the braided line, to replace it? Looks like my check valve is failing, because it is definitely now letting oil back, instead of just air in.

I have searched the forum, but can't find a how to, to take the check valve off. I am sure there is a simple trick to it, but my feeble brain just isn't figuring it out. Al I can do is get it to spin, can't find a way to disconnect it from the braided line.
 

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Discussion Starter #12 (Edited)
Heh, yeah, problem. What I did was to cut two short strips from a heavy duty zip tie. Total length the same as the diameter of the pipe. Then squeezed them in sideways under the braided line bayonet end to release the clips and allow it to be pulled off. Easier said than done though I'm afraid.

UPDATE: See my newer post below. The above is only necessary if you are removing one of the braided line ends from a place where there's no space to get a proper line disconnect tool in, such as (B) the pipe at the front of the valve cover.
 

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Heh, yeah, problem. What I did was to cut two short strips from a heavy duty zip tie. Total length the same as the diameter of the pipe. Then squeezed them in sideways under the braided line bayonet end to release the clips and allow it to be pulled off. Easier said than done though I'm afraid.
Just great. :lol::lol::lol:

I will wait until I have the new one in hand, so I can see how the clip works, then try your method. Thank you for the help.

The OEM is definitely bad, when I unplug it; there is plenty of oil sign. And enough oil has been getting though that there is evidence in the hose coupler between the charge pipe and IC on the passenger side. I did thoroughly inspect the IC and the oil sign ended just below the coupler. Nothing on the drivers side. And I even unhooked the lower "catch pipe"(still have the OEM IC on) to see if any oil there-nothing.

I actually discovered this when chasing down a small boost leak. The upper clamp (OEM Clamp) on the passenger side IC/Charge pipe had failed. And when I changed it out, I unhooked the hose for a look-oil sign. Remembering this thread and a couple others-took a look at the fricken check valve. And "There's Your Sign". :lol::lol::lol:
 

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Discussion Starter #14 (Edited)
Just great. :lol::lol::lol:

I will wait until I have the new one in hand, so I can see how the clip works, then try your method. Thank you for the help.
UPDATE: In the cold light of day, I realise that I may have misdirected you. I believe that a new check valve comes as part of an assembly, together with the braided hose. So you don't need to remove the valve from the hose, just the hose from the engine.

In THAT case, it's much easier since there's plenty of space, you just need to get an Fuel/Oil Line disconnect tool for a 3/8 line. Similar to:



Just close the correct-size end over the metal pipe on the valve cover and push into the braided hose end to release the barb-clips, then pull the line off. These, and variants, are available at all the usual auto part stores for well under $10.
 

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The quick disconnect that's close to check value is a bugger, in the end I used 2 quick disconnect tools and wedged them in one at a time. The single disconnect tool will not close enough due to the check value to get in on both sides.
 

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UPDATE: In the cold light of day, I realise that I may have misdirected you. I believe that a new check valve comes as part of an assembly, together with the braided hose. So you don't need to remove the valve from the hose, just the hose from the engine.

In THAT case, it's much easier since there's plenty of space, you just need to get an Fuel/Oil Line disconnect tool for a 3/8 line. Similar to:



Just close the correct-size end over the metal pipe on the valve cover and push into the braided hose end to release the barb-clips, then pull the line off. These, and variants, are available at all the usual auto part stores for well under $10.
:lol: I just came back home to look for a part number, because the one they had at the dealership is for the braided line and check valve. And the cost is $64.00. :lol:

The part number they show is 12598298. Do you have a part number?
 

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I have a new check valve/braided line assembly on the way. Picked up a fuel line tool-that works great for unhooking the assembly.

I pulled the OEM off the car and the check valve was definitely gooey and not working correctly. I hosed it out with MAF cleaner and now it works. :thumbs: The valve doesn't have a spring, it is just a simple vacuum valve. So I am thinking this might be a regular maintenance item on our cars. As oil builds up on the back side of the valve it will eventually get gooey and the valve will not seal good. I pulled my intake pipe and there was a snail trail of oil from the check valve inlet all the way to the turbo. And it continued down the charge pipe to the IC union where it finally dissipated. In my case, I caught it early enough that it really wasn't causing much of an issue. But I could see where a complete failure of the check valve would result in significant oil accumulation in the charge system. (I did pull the catch tube on the bottom of the IC and check for oil-just to be safe-no sign)

Thanks for the help, TS.
 

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Discussion Starter #18 (Edited)
Very good idea GS, I'll bet you're right! Makes perfect sense now you bring it up.

(UPDATE: Now added a descriptive photo to initial post)
 

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Been watching this thread and reading P9-729 in the Manual. Appears that a manometer test can verify the Crankcase Vent System.

I am going to take mine apart tomorrow....I think I am leaking!!:brentil:

BTW, there has to be a supplier of the check valve....why do we need to drop $64 for a $7 +/- part? Someone made it, we need to find out who!! :thumbs:
 

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Got up close and personal with the RH side of the Turbo this AM, was pretty dirty and oily....was thinking it was going to be a bad situation when I took it apart but maybe the moon phase is in my favor?

There was just a drop of oil in the bottom of the tube...Cleaned up easy and put it back together. I believe that the bottom clamp was just a bit loose???

31,375 miles ....YMMV :thumbs:

:driving:
 

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