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2011-2016 Cruze Limited 1.4L PCV System Explained

397K 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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#252 ·
Can anyone tell me what is a normal vacuum on the chevy 1.4 liter turbo and what is a normal crankcase vacuum measured at the oil dip stick? With everything operating normal with pcv my vacuum is 16 inches of mercury and at the oil dip stick is 3 inches of mercury which does cause a whistle sound.
 
#3 · (Edited)
De we have any idea of what type of check valve is used at the turbo, and what it looks like viewing through the connection of the corrugated tube? Wondering if this check valve could be cleaned and inspected without removal of the turbo.

I've seen something similar to this over on the sonic forum, but this is the first time someone has mentioned two check valves in the PCV system.

http://www.sonicownersforum.com/for...gine-discussion/10825-1-4t-pcv-explained.html
 
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#4 ·
De we have any idea of what type of check valve is used at the turbo, and what it looks like viewing through the connection of the corrugated tube? Wondering if this check valve could be cleaned and inspected without removal of the turbo.

I've seen something similar to this over on the sonic forum, but this is the first time someone has mentioned two check valves in the PCV system.
I don't have a picture, but if someone wants to pull theirs off and take a picture of it, I can post it. Don't know the answer to your other questions yet.

I haven't yet seen an article on SOF that goes into as much detail as I did here and you really have very little analysis ability if you don't even know there are two check valves. It took a fair bit of research for me to get this far.
 
#5 ·
Great write up! It really cleared up my understanding of our PCV system! With this new understanding though I'm now wondering why when someone has a PCV problem you usually only hear of them replacing the valve cover (burst disk), and GM has extended the warranty on it. Seems like its most likely that one of these other valves have failed causing the burst disk to fail.
 
#8 ·
Note that some of these can be failing from burst disk fatigue since the crank case is constantly under changing pressure, so you can't assume that every time one fails, that there's an underlying root cause.

Sent from my LG-D850 using Tapatalk
 
#6 ·
Nice write up! Thanks for taking the time to write this explanation.

Makes me realize how important it is to use good oil and good gas. Our 2007 Mazda 3s has 105,000 miles on it and still has the original PCV valve and doesn't burn any oil (PCV valve is hard to change because you have to take off the intake manifold to get to it - genius) and I have 50,000 miles on my 2011 1LT Cruze and still have the original PCV valve and I have never used any oil between changes. (knock on wood - hand hitting head :) I can still see the check valve in the intake manifold - yeah). All our cars are about 80% city driven. Not totally stop and go but not highway driven either. I try to take our cars out the weekend and drive them at highway speeds for about 10 or 15 minutes.
 
#16 ·
Deleting wouldn't be any worse then running without cats. If I were to do the delete Im not sure if the pcv hose from intake can be ran to a catch can and vented to the atmosphere and then plug the turbo intake end of hose. If epoxying the intake manifold where valve would be missing would that cause the crankcase to no longer be under a vacuum? If my nipple valve goes missing again and oil collects at the TB and out of 5y/100k PW I will be doing this instead of replacing whole intake manifold assembly.
 
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#17 ·
I don't know of any oil vapor that the catch can would catch, that the valve cover doesn't under normal operation. Every catch can I've seen installed on these cars does nothing but accumulate moisture, and a good baffled catch can would run you well over $150 for little to no real benefit. In a 15,000 mile oil drain interval (with AMSOIL signature series), I didn't consume any measurable amount of oil (the line on the dipstick was the same).

Closing off the intake manifold would cause the crank case to no longer be under vacuum. I don't think that would affect anything though. I'd be tempted to do the same thing if the intake manifold failed if there isn't an improved aftermarket solution.
 
#18 ·
Wasn't referring to having a catch can part of the loop. Would leave outlet hose of can open to the atmosphere. Maybe using a breather filter at end of intake manifold hose would work without the need for a catch can.
 
#25 ·
I just had my intake manifold checked and replaced by my dealership. I had the PCV valve/camshaft cover replaced in July for the second time. Question - if the intake manifold check valve is missing, will this cause a slight drop in power? I ask because my car has been sluggish this summer when compared to previous summers.
 
#28 ·
My intake check valve is missing. I just may try your theory of epoxy in the hole where the orange ******* should be. I installed a catch can yesterday on the PCV hose, so that should catch the oil mist. Hmmmm....
 
#29 ·
That's what I'm thinking. Catch can already installed. Now to clean and epoxy that stupid hole...
 
#31 ·
Fuel line Product Hose Auto part Metal

I thoroughly cleaned the holes where the orange flapper used to be using Pro Goof Off and Q-tips, and dried it well using a shop vac with small tube attachment. Then I used JB Water weld stick putty and pushed that in the holes with a small resin spatula, then let it dry for 2 hours. I then came back to finalize the seal with JB Weld epoxy resin, spreading it down in there with a resin spatula also. I have let it dry all weekend and will drive it tomorrow morning for the first time. I will also post some pics of the catch can installed later. I will post updates of what happens...
 
#32 ·
Probably should remove vac hose off the bottom chamber of the intake also. Only problem i see is there is no crankcase evac at high vac conditions, when this is sealed off. The vent at the turbo works due to suction on the turbo inlet when boosting, when there is enough suction , hard to know. So with the orange valve sealed off, you have no venting. Good idea would be to run a vac gauge and see how much time is spent with vacuum on plus side. I still don't understand the the burst disc in the valve cover ? I would think a better deal, remove intake install nipple in vac chamber and use an external check valve in line to intake. that way its replaceable. It would have to have a low cracking pressure, and be able to withstand vac as well as boost pressure. Greg
 
#33 ·
The vent at the turbo works due to suction on the turbo inlet when boosting, when there is enough suction , hard to know.
The turbo inlet is also just the filtered side of the air filter. I wouldn't expect much vacuum at all. I think that connection is just so any gasses that come out from the crankcase goes into the engine to be burned instead of vented to the atmosphere.


I would think a better deal, remove intake install nipple in vac chamber and use an external check valve in line to intake. that way its replaceable.
I'm not sure how you'd be able to set up a external check valve. It might be possible if there's another port with access to the intake itself.
 
#35 ·
Most turbo engines currently have 2 paths for crankcase venting-remember that when under boost there is no vac. so the gases have to have some where to go, you get more crankcase pressure under boost that's why there is a vent in the turbo inlet. But it has a check valve by the outlet, and yes suction is created there, faster the compressor spins the more there is. the worst part of the stock system is the little orange check valve--which fails with regularity. I found some check valves with .5lb cracking, and high vac and pressure values. I am thinking you would want to approximate the area of the original holes, run though a reducer to the original vac hose connection on the solinoid. Just bypassing the original orange valve.
I have seen some manifolds with the orange valve gone that are coated with oil inside. Not sure the stock system (valve cover) does such a great job of separating oil and gas. g
 
#39 ·
We can't assume that the oil coating the intake manifold is coming through the PCV system. When we produce positive crankcase pressure, or rather we lose negative crankcase pressure, we potentially push oil past turbo seals. I don't know if there's a restriction on how much PCV gas can flow through the check valve in the turbo inlet.
 
#40 ·
Question? I was replacing the cam sensor seals today, along with the turbo oil feed line on my '13 LTZ RS. I am going to do a valve cleaning tomorrow with CRC Intake Valve Cleaner. www.youtube.com/watch?v=siRwcnj8-OE While working on the car today, I had the air box and all of the duct work off going to the turbo. I noticed a nasty oil/gunk trail coming from the hose with the check valve and it was going directly into the turbo. Can I use this product to clean it, or is there something better out there that you guys use? Should I not worry about it? CRC claims this is safe for turbos.
 
#46 ·
So, I had to order a new check valve. Parts came in today but the check valve I ordered won't work. It has a break pressure of 3 psi, which I didn't think would be a big deal until I realized that we don't really get much more than -3psi of vacuum under normal driving conditions, so.....had to find another.

Good news is that I found one, with a better design for longevity and a 1/2 psi break pressure. Bad news is it costs more and has to be ordered from Grainger, which also means you tack on $10 shipping. All in all, the change will increase costs by ~$20.

I've run this by several people over on our Facebook group who have been involved in this problem and they all agree it's a very good design that will work very well. I will be publishing the parts list for everything and will give you the option to either order all of the parts individually yourself, or pay me to piece everything for you and mail it out as a kit. 4. Total cost of parts will be $110 excluding a 6-8" length of oil hose you'll also need and a sealing washer if you order the parts yourself, and I'll probably charge $30 to piece it all together and ship it out for you. You'll still be responsible for actually assembling everything, but anyone with basic hand tools can do that.

It's a solid design with a serviceable check valve that will almost identically imitate OEM functionality and may never have to be serviced again for as long as you own the vehicle. It will be mostly hidden from view but serviceable without removing the intake manifold and should be wholly leak-free.

While I understand $140 is a high price to pay, it sure beats spending $280-$350 on a new intake manifold only for it to fail again. GM seems to have no interest in redesigning this and Dorman is dragging their feet in releasing a redesigned system that doesn't have this problem. I kept part costs as cheap as possible. Once I publish the parts list, you'll be free to source identical parts locally and build it yourself, but I do strongly recommend that you use the same check valve; there really aren't any others I came across that would work. Stay tuned.
 
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