1.4T PCV Explained

[BoostedSnail]

Basically ive personally replaced the coil pack and valve cover and turbo. Im going to be cleaning the residual oil in my car from my so called blown seal turbo that has crisined my charge pipes and everything with a fat coating of oil. Im doing this tomorrow and reinstalling everything hoping that this will stop my smoking and misfiring issue. Im installing a catch can just to help a little im not saying this is going to stop the dumping of oil into my new turbo but it should help a little correct? sorry for the bad spelling here guys at work and double tasking typing and helping people. Ill keep you updated, my only concern is this damn pcv line dumping a nice amount of oil into this new turbo. Im really starting to hate this car im not going to lie.

 

[Preloader]

BSnail's case is a prime reason why I started this thread. We've lost quite a few 1.4T enthusiasts over this oil problem.

Without physically inspecting the car myself, the best I and others that are trying to help can do is suggest things to look at.

That's what keeps leading me back to the PCV system.

I know BoostedSnail's turbo needed replacing anyway, but there was a Cruze owner with the same oil problem who's dealer told him it was a turbo. They replaced it and the problem persisted.

Replacing expensive parts without troubleshoot elimination will make anyone upset at their car.

I'm hoping to find a "eureka" light bulb solution to this problem.

There can only be so many ways oil can make it into the charge piping. Bad rings, bad seats, bad turbo, bad crankcase seal, or bad PCV system.

In some cases, the majority of those have been ruled out, at an expensive price tag and the problem has not resolved.

Has anyone with this issue maybe overfilled on an oil change? I refill with about 3.8L of 5w-30.

 

[KartRacer]

Preloader
I am not experiencing any of these issues at this time, however you state that you add 3.8 qts? Specs call for 4.2 I believe. This quantity results in a full indication on the dipstick.
Now if people are putting the full 5 qts in, well that could easily be a problem resulting in all of the oil issues.

 

[BoostedSnail]

BSnail's case is a prime reason why I started this thread. We've lost quite a few 1.4T enthusiasts over this oil problem.

Without physically inspecting the car myself, the best I and others that are trying to help can do is suggest things to look at.

That's what keeps leading me back to the PCV system.

I know BoostedSnail's turbo needed replacing anyway, but there was a Cruze owner with the same oil problem who's dealer told him it was a turbo. They replaced it and the problem persisted.

Replacing expensive parts without troubleshoot elimination will make anyone upset at their car.

I'm hoping to find a "eureka" light bulb solution to this problem.

There can only be so many ways oil can make it into the charge piping. Bad rings, bad seats, bad turbo, bad crankcase seal, or bad PCV system.

In some cases, the majority of those have been ruled out, at an expensive price tag and the problem has not resolved.

Has anyone with this issue maybe overfilled on an oil change? I refill with about 3.8L of 5w-30.

you know what boss now that i think about it I may have overfilled my oil? in that case if i drain the oil i have now and refill it with the correct amount could that be the problem as well. and if thats the problem have i perminently messed something up at this point?

 

[Preloader]

Well overfilling could definitely cause issues. That's why the PCV is ALWAYS at the high point on any engine. To avoid oil particles easily making making their way in.

As fas as the 4.2L of oil. Is that gross oil volume, or recommended fill at oil change? I don't recall. I just do it old fashion, a.k.a. manually check the dipstick after a short drive and brief cooldown. I shoot for the halfway mark on the dipstick. And 3.8L has aways done the trick for me.......

And I have had less oil evidence into my compressor than anyone on here. Maybe we are getting somewhere. I feel no need to see my dipstick wet to the top maximum.

I aso do changes EVERY 3,000, so I'm not worried about hurting anything with a slight oil deficit.

 

[mitdr774]

How is the oil return set up on the 1.4? Is it something that could easily become restricted and cause oil to back up into the center section of the turbo? I know that some vehicles use a fairly weak material that can actually collapse in on itself.

 

[Preloader]

It's fed directly from the oil filter housing, and the return is a hard line to the oil pan.

It's doubtful it is a likely failure point.

 

[BoostedSnail]

we shall figure this out muahahahahaha

 

[rcmn0022]

Well overfilling could definitely cause issues. That's why the PCV is ALWAYS at the high point on any engine. To avoid oil particles easily making making their way in.

As fas as the 4.2L of oil. Is that gross oil volume, or recommended fill at oil change? I don't recall. I just do it old fashion, a.k.a. manually check the dipstick after a short drive and brief cooldown. I shoot for the halfway mark on the dipstick. And 3.8L has aways done the trick for me.......

And I have had less oil evidence into my compressor than anyone on here. Maybe we are getting somewhere. I feel no need to see my dipstick wet to the top maximum.

I aso do changes EVERY 3,000, so I'm not worried about hurting anything with a slight oil deficit.

Most of the time, the difference between full and low on the dipstick, is about 1 qt. This translates into about 946mL. Half of it is 473mL and when you add that to your 3.8L that translates into nearly 4.2L

Just pointing out why your 3.8L is off from the 4.2L spec that everyone else is mentioning

 

[Preloader]

That explanation helps. Just pursuing all trains of thought here on the oil problem.

Let's say at factory max 14psi, the suction on the PCV is not enough to drag much oil (filled with 4.2L) with it.

Now you tune to achieve 22+psi...... Suddenly the suction increases dramatically!

Maybe the oil being .375" lower (3.8L) in the tiny little engine prevents the extra PCV suction from kidnapping oil.

 

[rcmn0022]

So from what you are saying, maybe a simple restrictor can be placed in line of the hose going to the turbo inlet.

Or, a custom intake manifold that deletes the system for people that are pushing extremely high boost in race only scenarios?

 

[Preloader]

Interesting ideas. I'd love a custom Intake Mani.

But I wouldn't want to delete the WOT portion of the PCV system. It not only helps oil integrity, but also promotes good sealing.

The restrictor idea sounds very doable.

 

[rcmn0022]

I was more thinking along the lines of a breather type of delete. That way excess can escape.

 

[Preloader]

Air breather won't work. I was interested in that idea too. But our PCV is a "closed" system.

If you vent it, you'll pull unmetered air in at idle, or you'll lose effective venting at WOT.

 

[carbon02]

Where is the rupture disk? Across from the oil fill cap?

Also this may help explain the "rupture disc" in the valve cover.

Let's say the orange check valve fails..... Suddenly the crankcase will be exposed to 14-24psi boost. Not a good thing!

The rupture disc would fail (or succeed technically) making a huge mess in the engine bay, but saving the engine in the process. I think Martyr Disc is a more appropriate name.

Is this rupture disk located directly accross from the oil filler cap on the valve cover? If so, this explanation explains the leaky valve covers we're seeing over on the cruze forums.

I've read the service manual discription, and it didn't "sink in" as well as seeing the parts.

Thanks Preloader for showing so many pictures

 

[Preloader]

Yes. The "rupture" disc is across from the oil cap. Once that disc fails, the PCV will draw all kinda of oil from the crankcase, because the crankcase is no longer sealed.

The pics in this thread are of a '11 Cruze 1.4.

 

[ChrisJ]

That explanation helps. Just pursuing all trains of thought here on the oil problem.

Let's say at factory max 14psi, the suction on the PCV is not enough to drag much oil (filled with 4.2L) with it.

Now you tune to achieve 22+psi...... Suddenly the suction increases dramatically!

Maybe the oil being .375" lower (3.8L) in the tiny little engine prevents the extra PCV suction from kidnapping oil.

Not only are you producing more suction, you're also producing more blowby and therefore more volume through the pvc system as well.

 

[Rockymoutain driver]

Hesitation during acceleration at high R.P.M.

Great info, thanks for that view. Seems to me that a filter/sponge needs to be used inline of PCV tube in a glass filter, to see when needs to be cleaned/changed. Also, don't understand why line is before intake tube and not after turbo unit. I seems...stupid to cause potential problems to turbo blades.
Really that will only help the turbo. As I wrap my head around this article on the gases/oil going direct to intake manifold during idle, wonder about my 10-15 min warming idle time every morning. That would cause the gases/oil to build in the intake manifold to start settling or coating surface area and getting into MAP sensor. So, I would have to add threading to sensor tube and install a filter screen at min, right?

 

[ChrisJ]

Hesitation during acceleration at high R.P.M.

Great info, thanks for that view. Seems to me that a filter/sponge needs to be used inline of PCV tube in a glass filter, to see when needs to be cleaned/changed. Also, don't understand why line is before intake tube and not after turbo unit. I seems...stupid to cause potential problems to turbo blades.
Really that will only help the turbo. As I wrap my head around this article on the gases/oil going direct to intake manifold during idle, wonder about my 10-15 min warming idle time every morning. That would cause the gases/oil to build in the intake manifold to start settling or coating surface area and getting into MAP sensor. So, I would have to add threading to sensor tube and install a filter screen at min, right?

After the turbo is very often under pressure and not vacuum, this is the entire reason for that line vs the one built into the intake.

 

[NewZJ]

Is this a PCV problem or do I need an oil catch can or is this normal?

Edit: Compression test shows one cylinder has half the pressure of the others, possible ring failure