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2011-2016 Cruze Limited 1.4L PCV System Explained

399K views 261 replies 67 participants last post by  Diesel Dan 
#1 · (Edited by Moderator)
2011-2016 Cruze Limited 1.4L PCV System Explained


Video:
I made a video to help better explain how this whole PCV system works to supplement this article.


Overview:
The purpose of this post is to explain the function of the PCV system in the 1.4L Turbo engine so those of you who are having issues or trying to help people have some idea of what is going on and where to look for potential trouble spots. We will start by assuming you know what a PCV system is designed to do. If not, stop here and go to google. Return when you understand the basics of what A PCV system does. Basic mechanical knowledge is required. I will attempt to explain this by walking you through the path of the PCV system. Below is an outline of the whole system and the direction the PCV gas flows, and each step will include any pictures I could find that show the actual component described. The terms "non-return valve" and "check valve" are used interchangeably. A check valve allows a gas or liquid to move in one direction but not another.




1 We start with the crankcase that has built up pressure, under a normal operating vehicle. We exit the crank case through the cylinder head at the two long ports at the bottom of the following image.

2. Those two ports feed into the valve cover, at the two long ports on the right side of the image below.



3. From there, we travel through a baffled oil separator system. THIS IS WHY WE DO NOT NEED A CATCH CAN. This pathway inside the valve cover is tasked with separating oil vapor from the PCV gas traveling through it. From there, we exit into the small port on the left (refer to arrow at the left of image above), to go back into the cylinder head. Notice the corresponding port on the cylinder head (arrow at the top of the image)?



4. Next, we find ourselves in the intake manifold, which is pictured below. Inside this port, there is a check valve (which GM refers to as a non-return valve), pictured in the next two images. Note, this is not a ball (as it has been previously referred to). It is a non-return/ check valve, that more closely resembles a specifically shaped nipple.




5. A corrugated hose comes out of the intake manifold, which has an open path from the PCV system and does not have to go through the non-return valve.

6. We arrive at the top of the below image, where there is ANOTHER CHECK VALVE.



7. Lastly, we exit to the turbo housing at the turbo's inlet (see oil streak above).

In case you missed it:
The crankcase is under vacuum whenever the engine intake is under vacuum; the check valve valve in the intake manifold opens and pulls all crankcase gases while keeping the check valve at the turbo inlet closed. When the engine produces boost in the intake (during acceleration or uphill driving), that check valve closes due to the air pressure inside the intake manifold, because we don't want to pressurize the PCV system. When this happens, the extra crankcase pressure is relieved through the check valve at the turbo inlet. PCV gas at the intake manifold check valve flows into the intake manifold but not back into the PCV system, and air at the turbo inlet housing flows into the turbo inlet, but not back into the PCV system. Both check valves allow PCV gas back into the intake; one before the turbo and one after the turbo. I want to make sure this is clear.


When things go wrong:

What happens if the check valve in the intake manifold fails (Step 4)?
  • Excess vacuum is produced on the PCV system internals when intake is under vacuum, which may pull more PCV gas than the oil separator is capable of filtering. Excessive intake vacuum may be applied on the crank case, which may also cause premature failure of the regulator diaphragm.
  • Boost is leaked from the intake manifold into the PCV system. You may not notice this happening until more symptoms show up. The boost leak seems to overwhelm the flow capacity of the check valve at the turbo inlet, and causes positive crankcase pressure. This positive crankcase pressure then causes the turbo to leak oil internally, the CPASV seals to leak, the oil pan gasket to leak, and oil to trip from the throttle body at the connection to the intake tube.
  • Excess positive crankcase pressure caused by the boost leak will cause the burst disk in the valve cover to rupture. Since the check valve itself may not show any other symptoms of failure, you may find yourself constantly replacing intake manifolds until you address the root cause.
  • In the event that the turbo inlet check valve is stuck in addition to the intake manifold check valve disappearing, oil consumption will increase. See below under "if you are burning oil."
Notes: The intake manifold check valve can either disappear completely due to fatigue (it's rubber after all) and be ingested by the engine through the intake, or it can be stuck open. To inspect this check valve, pull the corrugated hose off of the intake manifold, and shine a light in there. If you see nothing, dip a cotton swab in rubbing alcohol and clean the side facing the vehicle's firewall as far down as you can since it may just be dirty. If there is still nothing there, your check valve is gone. IMPORTANT: failure of the check valve does not automatically result in elevated oil consumption.

What happens when the check valve at the turbo inlet fails (Step 6)?
  • In the event that the check valve at the turbo inlet is stuck closed, the burst disk can fail.
  • Excess pressure will build in the crank case, which will prevent the turbo bearing housing from draining oil, and will seep oil past the turbo seals to be burned in the exhaust or through the intake. (Walker Morgan noted this one). In the event that this occurs, oil consumption will increase.
Notes: If you are burning oil, remove the corrugated line and blow into it. If it does not blow freely, your check valve is stuck closed. Wipe the oil from your mouth, and replace it. A second possibility is an intake manifold gasket failure around the PCV ports in the first picture above.

What happens when the PCV regulator diaphragm (Step 8) fails?
  • Excess vacuum or boost produced on the PCV system by the intake manifold check valve (whether or not it is good) being open will cause unmetered air to flow through the vent on the cap and may trigger a check engine light. Refer to "related service codes" at the end of this article. You will hear a hissing sound in the engine bay.
  • If the either of the above check valves have failed, you may find oil vapor sprayed in the proximity of the cap vent.
Notes: The PCV regulator diaphragm may fail from fatigue, or it may fail in the event that either of the PCV check valves fail and cause excess vacuum or excess PCV pressure. A failed PCV regulator diaphragm may or may not be a symptom of another root cause.

What happens when the corrugated hose fails?

- The corrugated hose may crack and develop a vacuum leak. If this happens, unmetered air will enter the the intake under vacuum when the intake manifold check valve is open. If severe, this may trigger a check engine light. Refer to "related service codes" at the end of this article.

What to do if these components have failed:
http://www.cruzetalk.com/forum/129-...-replace-valve-camshaft-cover-1-4l-turbo.html
No tutorial currently exists for replacement of the intake manifold, the corrugated hose, or the turbo inlet check valve. Any volunteers?
- I've presented a retrofit solution for the intake manifold check valve failure in the following thread that will cost 1/2 to 1/3 that of a new intake manifold while lasting much longer:
http://www.cruzetalk.com/forum/34-g...urbo-intake-manifold-pcv-check-valve-fix.html

Related Service Codes:
P0106 P0171 P0299 P0507 P1101 P2096
 

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#101 ·
Take a look at the link I posted in #89. In those systems, the air is restricted when it goes from the crankcase to the intake, so there's no code if you leave the oil fill cap open on them. Ours seems to be designed differently, but I still think there's a fresh air intake somewhere.
 
#105 ·
I did review that link. There is no source of inlet for air on this engine with the exception of the air intake. If you think there is one, get a can of starter fluid and start spraying everywhere. It would obviously only happen under vacuum, so if you feel engine RPMs rise, you'll know why. Trust me, it won't happen. That burst disk is sealed shut until something causes it to rupture, whether it's old age or excess pressure or vacuum.

Another reason it won't happen is because that air isn't filtered. It would cause endless problems if you lived in exceptionally dusty regions.
 
#104 ·
I started to have this issue with my 2012 LT RS Cruze. I got the following codes: P0171, P0106 and P1101. I did get the P0301 misfire but it was due to the 3 codes listed before. We did some research and found the following COULD be wrong with the car: Valve cover, O2 sensor, MAF sensor, MAP sensor, ignition coil or PCV hose. I was having the same issues as reported on several other threads... check engine light was coming on, then the traction control/stabilitrac warning. The car would idle extremely rough, pulsing between 500-700 RPMs. When I would turn the car off, my fan would kick in and run for a bit as well.

Here is what we replaced (and did not fix the issue):
Valve cover and gasket
Ignition coil
MAF sensor
spark plugs
Seafoam cleaner
Lucas Oil Injector Cleaner

After more looking (my brother did a lot of research and testing with my car) and discovered 1 part we overlooked. The PCV valve tubing (GM part# 25193343). The tubing was so brittle and hard that it has broken down near the connector, under the exit turbo enlet. We replaced the part with a heat hose and it fixed the issue! We put the old ignition coil on to test, and it was still good. We also tested the old MAF sensor and it worked as well. We did keep the new spark plugs, as those needed to be replaced anyway. And we still think it needed the dreaded valve cover replaced as well. All in all, instead of spending $800 at the dealership to get it fixed, we spent around $140 (not including the beer I paid my brother for the work). I wanted to post this for those having issues and to make sure that you look at all the possible spots. This one was a little hidden.

here are some pics of the hose (old and new):
Factory PCV hose:
Auto part Engine Vehicle Wire Car


PCV hose removed from the car. It broke near the connector.

Screw Auto part Suspension


New hose that is on the car now and fixed the issue.
Engine Auto part Vehicle Car Family car
 
#185 ·
I started to have this issue with my 2012 LT RS Cruze. I got the following codes: P0171, P0106 and P1101. I did get the P0301 misfire but it was due to the 3 codes listed before. We did some research and found the following COULD be wrong with the car: Valve cover, O2 sensor, MAF sensor, MAP sensor, ignition coil or PCV hose. I was having the same issues as reported on several other threads... check engine light was coming on, then the traction control/stabilitrac warning. The car would idle extremely rough, pulsing between 500-700 RPMs. When I would turn the car off, my fan would kick in and run for a bit as well.

Here is what we replaced (and did not fix the issue):
Valve cover and gasket
Ignition coil
MAF sensor
spark plugs
Seafoam cleaner
Lucas Oil Injector Cleaner

After more looking (my brother did a lot of research and testing with my car) and discovered 1 part we overlooked. The PCV valve tubing (GM part# 25193343). The tubing was so brittle and hard that it has broken down near the connector, under the exit turbo enlet. We replaced the part with a heat hose and it fixed the issue! We put the old ignition coil on to test, and it was still good. We also tested the old MAF sensor and it worked as well. We did keep the new spark plugs, as those needed to be replaced anyway. And we still think it needed the dreaded valve cover replaced as well. All in all, instead of spending $800 at the dealership to get it fixed, we spent around $140 (not including the beer I paid my brother for the work). I wanted to post this for those having issues and to make sure that you look at all the possible spots. This one was a little hidden.

here are some pics of the hose (old and new):

Factory PCV hose:
View attachment 216898

PCV hose removed from the car. It broke near the connector.
View attachment 216906
View attachment 216914

New hose that is on the car now and fixed the issue.
View attachment 216922
How did u remove the end that DOESNT have the pin clip ?
 
#106 ·
Since I need to drive my car, and while these parts come in, I think to myself, would sealing the intake pcv port off now cause issues? The turbo would be sucking the pcv gasses but it does that in boost anyway and these cars run boost from 2k on. Not a permanent solution. The burst disk is already blown so it wouldn't over pressurize.


Sent from my iPhone using Tapatalk
 
#107 · (Edited)
There is a sonic owner who did exactly that, and has been running it that way for some time. He just plugged up the check valve port and left it as is. I don't recommend that for a few reasons, but it hasn't caused him any immediate problems. You'll be fine running it like that for a few months, but I'd still replace the valve cover as you'll be venting PCV pressure through there as well and making a mess of your engine bay.
 
#113 ·
There were a couple areas where I thought I might get a flat enough fixture on the outside, but I finally talked myself into going with the throttle body spacer. On the input side, your nut is captured by the intake itself, and once you put the angle fitting on it, it's not really going to spin off and drop parts into the engine. Pretty much anything, even ugly epoxy, was not going to be as secure, and it's also in a worse place - anything falling off is going to go right into the engine and either jam a rod or bounce around on the piston.

I don't think it's a check valve - I agree that pressure differential across the input and output is not going to close it in either direction. It's a vacuum regulator - it compares the pressure inside the chamber to the atmospheric pressure. It would close off the crankcase from either ventilation system when vacuum was too extreme, although without rigging something up to connect to a good part, I couldn't begin to guess the pressure.
 
#114 · (Edited)
Uhh, found this ventilation module on Imgur, system on a modern PT:

*Note the detail that looks just like the thing that blows out on the 1.4 valve cover..."Burst Disc", "PCV Fuse"



The pressure control valve in the ventilation module also serves to regulate the pressure in the crankcase. The new ventilation module improves fine oil discharge up to 80%. The engine also has a PCV system in the engine block, which is active in partial and full load.

Dotted is Old, Red is New and Improved:



 
#118 ·
I wasn't aware the 1.4T ventilation/PCV system is completely understood. AFAIK, everyone is riding speculation as to what the "PCV fuse" really is for and when/why it is needed; in addition, there is a lot of speculation riding on the efficiency of the valve cover baffles to capture oil mist.

For those who are curious, they can draw their own conclusions regarding the quite relevant ventilation system information I posted found on other modern powertrains. You can take in the information and draw your own conclusions, I find it hard to believe you are not curious about modern ventilation/PCV systems because maybe it could lead to enlightenment about the 1.4T ventilation system.
 
#121 ·
To me, XR's setup seems sound. As complicated as the PCV system may seem; I have found that the most simple setup with reliable hardware is the best path to take! All we really need at the check valve point is no charged air entering the PCV chamber when boost is applied.. and a solid source of air flow, in a positive direction, to create the required Venturi effect, to recirculate crank case pressure from bottom-end blow-by. The TB spacer is positioned in a great place for the Venturi effect to exist and there is a minimal amount of hardware to create a "pooling" condition...And what hardware is supplied can be repositioned to further reduce the chance of fluid build-up. Moisture build up in the crank case is a major concern to me. Crank case moisture is more prevalent in the winter and I don't want that moisture to get sucked out with the crank case gas, only to pool up and freeze the modified PCV/OCC system, when extreme cold weather hits. It has happened to both of my past boosted builds (Evo8 and Mazdaspeed3) from not buying a well designed/tested OCC system. Moisture is especially bad when you are setup and tuned to VTA the crank case pressure instead of recirculate. Just when you think yo s$*t is blown (turbo seals/piston rings); you dig and find out it's just a froze up PCV valve or OCC line. XRs setup seems to attack both of my primary concerns: correct flow and minimizing the chance of a frozen system.
 
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#124 ·
Mine was really tough to pull off too. .. and tough to put back on.

Mine had a plastic washer and rubber o ring.

Intake | plastic washer | rubber o ring | pcv hose

I can try to get a pic for you since mine hasn't been put back together yet.
 
#128 ·
I'm not quite seeing the evidence that it acts as a regulator. Intake vacuum is really not low to begin with, crankcase positive pressure needs to be vented somehow or the turbo bath will fill up with oil and you'll have even bigger problems.

What would be the point of GM producing a vacuum regulator? In most conditions, we don't really see much more than 6 inHg to begin with.

I also struggle with the concept of it being a restriction, since that would theoretically build up positive crankcase pressure under extended high load use.

Let's not forget there's a vent on that cap. That's there for a reason and it's not to pass air under normal operating conditions.

Sent from my STV100-1 using Tapatalk
 
#133 ·
I'm not sure what the point would be to regulating crankcase vacuum unless there is a risk of damaging the crank seals, but I'm certain it's a regulator. From what I've seen of teardown photos, you have a center hole which routes to the intake manifold and an outer ring that routes to the crankcase underneath that diaphragm. The top of the diaphragm is atmospheric air and there is a spring lifting the diaphragm off the seat.

If crankcase vacuum becomes too high, atmospheric pressure pushes down on the diaphragm and closes off the center hole, cutting off or at least restricting the vacuum supply from the manifold. In cases where there is pressure or insufficient vacuum in the crankcase, the diaphragm is kept lifted off the seat by the spring and this pressure, allowing no regulation to occur. Most PCV valves have some sort of regulation similar to this; it's just all self contained into one unit. A regulator also explains how GM can call out a very narrow range of acceptable crankcase vacuum. Additionally I've also noticed while testing mine after bypassing the intake check valve that the crank pressure would momentarily spike to >15" when I initially plugged off the dipstick hole with the gauge and then would settle down to a very steady 12"; I suspect I was seeing that regulator at work.

I've also seen a few here quote 12 inHg for crankcase vacuum, but they need to realize it is 12" of WATER, not mercury. There's a big difference there.
 
#138 ·
So I have noticed that for the past couple of weeks my car has been smoking only at high RPM's on the freeway. The car is not giving any symptoms that something is wrong, the car runs good with no hesitations and no check engine lights. I received this write up on how to manually fix the issue for the smoking from Andrei Pop. which I'm considering on pulling the trigger on it here shortly, but after reading this thread, could there be more problems that this fix will not correct? Could it be that the turbo is going bad? Could my PCV be bad as well? What about piston rings? other issues? I know Andrei Pop already facebooked me in regards to this, but I just want to double and triple check that the solution to me smoking cars in the freeway (not racing lol) could end by doing this alternative fix on the intake manifold. Any input on this will be greatly appreciated. Thank You.
 
#139 ·
I'm Andrei, just FYI.

Use the pcv issues thread also in this section to help you diagnose. If the valve cover is bad, there will be suction at the vent. If the intake manifold check valve is gone, you'll be able visually verify.

The smoking may be caused by a number of things, but the PCV system is the cheapest to repair first.



Sent from my STV100-1 using Tapatalk
 
#142 ·
Hi I read just about all of your threads and so I havea13 cruze lt turbo with 73000 miles.do I need to worry about this on my car? I'm not having any problems and I have a trifecta tune and K&n intake just curious if I need this and what should I be looking for exactly? I already had to replace the water thermostat cover on the drivers side that has 4 hoses attached to it.it had a small crack leaking antifreeze
 
#144 · (Edited)
I have a '13 Cruze 1.4 turbo which we bought new, now has about 140,000 mostly highway miles on it, and last week it did the thing with the check valves - loud hiss from the valve-cover PCV valve,diminished GPM, searching idle, P1101 code,etc. Using our spare car now. If we were to drive the Cruze in question,would it do some damage? Like,burned valves, for instance? Need to fix it before driving any more? I'd like to get this kit, but due to circumstances, I need to get this fixed promptly, and the Bad News Racing site causes me to get a warning about phishing and dangerous site,etc.,so I guess I'll just order an OEM valve cover and intake, which include the parts I need. Is buying those items going to be enough to fix this? What about that check valve at the turbo? Do I need one of those, too? Never had any trouble with this car, and it's averaged over 40 MPG over its entire life. The transmission started whining at about 100,000 miles, and I have one ready to install,along with the other necessities of that swap. The local dealer replaced the water pump due to the recall some time back. I appreciate any input you may have.
 
#145 ·
The BNR site should be fine. I'll mention it to Jerry. I would honestly recommend getting the kit for the intake manifold. You can drive that bad intake manifold a little while without any serious issues but the valve cover does need to get replaced, so do that ASAP.

As for the turbo Inlet check valve, pull the corrugated hose from the intake manifold and blow in to it. If it flows freely, that doesn't need replacing.

I can have a kit out to you tonight if you order one.

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