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Burning 2 quarts oil every 1k miles, re-route kit pulling too much vacuum?

2265 Views 21 Replies 8 Participants Last post by  chilehed
This is a partial continuation of this thread Rich/smoke at start up, occasional burn smell, sluggish...

I mentioned I installed the pcv re-route v3 and ever since it seems like it's been burning oil, almost to the day since it was installed. I originally thought it was a coincidence with the valve cover I replaced at the same time, and discovering a crack in the turbo. Well now it seems like the re-route kit might be the culprit. The line coming out of the intake manifold and going to the turbo intake is absolutely covered in oil from end to end (on the inside). I can see the glue is still holding up in the intake manifold (where the red valve originally was) and is also covered in oil, so it shouldn't be a case of blowing intake pressure back into the crankcase.

Since installing the re-route kit I've installed a new turbo and virtually all seals accompanying it (coolant lines, oil cooler seals, etc.), and a new valve cover (the seal is still good and not sucking/blowing air).

I think at this point I may just install an oil catch can inline with the large pcv line. Any ideas why the pcv kit would cause such a dramatic change in crankcase vacuum that it's pulling oil out and burning it? Or alternatively why there's such an increase in oil vapor that is getting pulled through the piping? I thought the valve cover had an oil screen to catch and return oil and only allow air/vapors through the pcv system.

On a side note, what is the black cover with a hard, small line connecting to it, held on by three bolts on the turbo for? I've seen it referenced as a diverter valve, but not sure what it's function is. Is it a secondary waste gate of sorts?
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You make sure the check valve is installed correctly? Sounds like it might be backwards.

Reach out to Andrei if you're having trouble with the kit - he will probably know immediately what's going on.

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Discussion Starter · #7 ·
I installed a genuine GM turbo. The check valve was installed correctly, double checked by blowing through it to verify the direction was right. The intake elbow post-turbo does have oil in it, as does the intercooler. All traces point to it getting sucked up through the pcv tubing (the larger one, not the smaller one with the check valve), and it going through the turbo and ultimately into the engine. There's oil leaking at the intercooler attachment due to so much oil getting through it. This is the exact same problem pre-turbo replacement, which is why I'm inclined to think its the pcv kit.

I might see about installing a vacuum gauge on the pcv line to see exactly how much vacuum its pulling, but I already know oil is getting through the entire line. Alternatively I could take the pcv off the turbo, leaving the smaller check valve/intake line, and see if my oil consumption goes away.

Off the top of my head, I may take the valve cover off and see if there is a baffle/screen to collect the oil from the pcv. I installed an aftermarket one instead of GM for that. Anyone know if there is supposed to be some sort of oil collecting screen/filter inside the cover? I know Duramax's and older diesels have a synthetic screen that looks like steel wool to stop the oil from getting pulled all the way through the intake.
 

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Discussion Starter · #9 ·
Switched to OEM valve cover, and there's been no change. I may install an oil catch can or a custom oil separator from scotch brite pads or something.
 

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Discussion Starter · #11 ·
Have you run a compression test? Any specific plug coated with oil?

The 1.4T engines are somewhat known for cracking pistons, and this may well be one of the signs.
I did compression tests before replacing the turbo, off hand I think the compression was 210 - 240 - 240 - 235. All of the plugs were wet with oil when I changed the turbo since it was burning oil through the intake. Using a bore camera, none of the pistons looked cracked. I can check again, but I suspect it will be the same (I don't see a piston crack forming/showing within 1k miles).

The pcv tubing is covered in oil, which if I understand correctly should just be dirty, maybe lightly oil, but not coated in oil on the inside. This does seem sudden, so I'm not ruling out a cracked piston, but all of the cylinders were oiled/carbon build up so I tend to believe it's being ingested through the intake and not from a cracked piston.

The other thought I have, learning from my older diesels, if the air filter is more restrictive than the pcv tube the vacuum on the pcv can become very large. My air filter still looks clean and new, so it shouldn't be more than normal. However, the new pcv route kit has a slightly larger tubing (I think?) than stock, making it more free flowing than OEM. I'm wondering if there is too much freedom in the new pcv tubing allowing too high of a vacuum to pull oil up the line. I may experiment with slightly smaller tubing to see if it reduces the vacuum pull.
 

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Discussion Starter · #12 ·
Investigated everything again post new turbo install. The PCV is not pulling oil, just lots of condensation. Using a bore scope/camera, cylinder 1 is wet with oil while the others are pretty dry, albeit carbon built up. I can't see any physical crack in the top of the piston, but doesn't mean they aren't covered by carbon. There is also oil sitting along the edge between the piston and cylinder wall. The cylinder wall still looks perfectly clean, cross hatching and all, no scratches or marred areas.

Not really sure how or where the piston failed, but looks like I'll be replacing a piston and rings soon.
 

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Investigated everything again post new turbo install. The PCV is not pulling oil, just lots of condensation. Using a bore scope/camera, cylinder 1 is wet with oil while the others are pretty dry, albeit carbon built up. I can't see any physical crack in the top of the piston, but doesn't mean they aren't covered by carbon. There is also oil sitting along the edge between the piston and cylinder wall. The cylinder wall still looks perfectly clean, cross hatching and all, no scratches or marred areas.

Not really sure how or where the piston failed, but looks like I'll be replacing a piston and rings soon.
The usual failure is actually between the ringlands - not all that uncommon on turbo cars (esp Subaru). The top of the piston will usually appear undamaged. The compression numbers still look better than I'd expect, but that one does appear to be down a little vs the other cylinders.

Quick search of a Subaru one, although there are pictures of Cruze pistons around here somewhere I'm sure. It's MORE common on the 16-17 Gen 2 1.4T, but the Gen 1's definitely saw it happen occasionally.

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Discussion Starter · #14 ·
That's an unfortunate place to crack a piston. Looks like I'll be tearing everything down and replacing them. Or a junkyard engine. Who knows. Lots of options when everything has to come off.
 

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Discussion Starter · #15 ·
Updating for future readers. None of the pistons were cracked at 158k miles, but replaced them anyway. The valve stem seals were likely the cause of my oil burning. Some seals were displaced and not fully seated plus being rock hard.

After a nearly full rebuild the engine is back together. Time will tell if the oil burning comes back.
 

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Discussion Starter · #17 · (Edited)
One thousand miles later and no oil loss. The oil is still light brown, not black or even slightly dirty. Using a Fram XG10246 for break in.

Compression test after rebuild is actually the same as before, cylinder 1 is down compared to the rest around 210 psi. Can only speculate the valves are not sealing as well as the others, or it's a purposeful design of that cylinder with slightly more recess in the head. Either way I'm not going to worry about it. Car is running good and hasn't thrown a code yet.

Here's some pics just because.

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Discussion Starter · #18 ·
Well, six-ish months later and still no oil burning. I might consider it fixed at this point. Oil analysis on first 1k miles oil change showed good filtration, expected wear levels for new components and seals. Will be doing a second analysis on the next change with 5k miles on the oil.
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I'd like to point out that excessive crankcase vacuum generally won't cause excessive oil consumption, although it will accelerate wear in certain areas of the engine (such as cylinder walls) because it pulls the oil back into the crankcase.

It sounds like what you're experiencing is excessive pressure, likely from blowby.

The PCV valve fix should reduce oil consumption if anything.
 

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I'd like to point out that excessive crankcase vacuum generally won't cause excessive oil consumption...
Yes, except insofar as the excessive vacuum might be indicating excessive flow through the ventilation system, so that the ability of the system to separate the liquid and gas phases is overwhelmed. That's why it's important to have the right orifice installed.
 
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