Burning oil - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Quiche2192 · 03-31-2019, 12:08 PM

My redtop has been burning oil only at idle and I've been going through some steps to try and fix it. But I thought I'd post about it here and see if anyone has some input for my specific case.

First of all, I looked up everything I could find about the issue and I found that this is usually related to a failing turbo. I still have the T25, and I checked the play in the turbo which is the only test I have performed on the turbo so far. It has about 1-2 mm of end play which I think is too much. So turbo will probably be changed out.

BUT

I also wanted to check engine compression just to see where it's at right now and this is what has me stumped.

I have 160 psi all around which is fine. But when I opened up cylinder 4, I found a lot of oil in the combustion chamber. I unscrewed the spark plug and it was covered in oil. There was so much oil that some spilled into the spark plug well.

So this what I am having issues with. What is causing all this oil to end up in just the fourth combustion chamber? The compression seems fine. I realize that oil can help seal the rings, fooling you into thinking the chamber has more compression than it actually does, but is that likely?

So what I wonder is, is the bad turbo causing the chamber to fill up with oil? I don't think that's likely. So then is it a bad pcv system? Mine's stock, but one part of the pcv system that I realized isn't quite ideal is that, from the t-fitting on the right side of the valve cover when looking at the engine from the front of the car, the line that is supposed to go to the intake pipe, right before the turbo, actually just has a small air filter on it. It's not connected to anything, it just goes to atmosphere through a filter. Could that be causing oil to pool up in the fourth cylinder? I can't seem to attach pics. I keeps saying upload of file failed...

So the steps I want to take are:
1. Change the pcv valve
2. Connect the T-fitting to the intake pipe right before the turbo (does anyone know of any intake pipes that have a fitting for this?)

I'll do this first and see how things go. If it still smokes after that but there's no oil in the combustion chamber, I can decide to replace the turbo. If there is oil, I'll need to rebuild.

What I wanna ask is, does anyone have any tips on how to make this process a bit easier? Am I thinking wrong about any of this? How do you recommend I run the PCV system from the T-fitting? Is the PCV valve a known failure point? And does a bad PCV system let oil pool in the combustion chamber?

jedi03 · 04-01-2019, 08:51 AM

usually a bad valve seal will cause oil to puddle in there...sometimes a bad ring. A leakdown test will let you know more, sometimes rings stick (my STI had this was going through a quart every 1k miles) and i ran seafoam through the whole block and fuel system, ran ATF in my gas (~1/2 quart to one fill up) and did a few oil changes way before they were due and it nearly stopped all consumption (only have oil vapors going through intake and see it puddled in the manifold) if there is excess blowby, your PCV system may need to be modified or your rings are going, the good compression suggests otherwise. The oil you found, is it coming from the sparkplug tube down or from the piston up? If going down could be failing valve cover gasket.

Quiche2192 · 04-01-2019, 01:34 PM

I'm gonna do a leakdown test next. But since you brought it up, I think it might be a bad valve seal or at least something to do with the valvetrain, cause it's in a less than ideal condition

*brndck* · 04-01-2019, 01:48 PM

also make sure the valve cover gasket isn't filling that plug bore with oil. the rubber that goes around the top of the spark plug bore does tend to leak over time.

still go ahead and do a leakdown test tho

Kingtal0n · 04-01-2019, 03:57 PM

Your on the right track.

Change the pcv valve. Take all the PCV hoses off the engine and wash them out with degreaser.

That includes intake and turbo side pcv

You may have the PCV routed incorrectly. Or a clogged restrictor. There is an OEM piece in the crankcase -> turbo inlet that sometimes gets clogged up with carbon deposits. take all the pre-turbo plumbing (rubber hose that holds air filter / maf) and wash it fully also.

The basic idea is: Once you've cleaned all the hoses. You will be able to clearly see if any oil is actively getting into them once you re-run the engine.

The cylinder full of oil: what I would do (do not do this if you are inexperienced)
Take spark plug out and wash the cylinder with some kind of solvent. Maybe brake cleaner but there is probably something less drastic. In the past I've even used tap water and then turned the motor over by hand with the plugs out to remove the water. Followed by cranking without plugs to further remove the liquid. Then brake cleaner it and let is all evaporate to dry again before putting back the plug.

Then put new plugs in it.

With all that cleaned up, everything oil spotless, clean plug etc... Re-run the motor then check periodically for oil. Then do another compression test if you see no oil to get a real reading.

Basically if the problem was in the pcv side, it will stay clean once you do all that. But if you have a broken piston ring the oil will instantly re-fill the cylinder/plug while all the pcv hoses stay clear and clean. The only warning here is that the intake manifold might also need cleaning. It could be holding alot of oil if the pcv is at fault, meaning it could simply re-supply the cylinder with oil. So you may also consider removing and degreasing the intake manifold along with all this other stuff. If you find the problem was in the PCV system then it also probably means the head ports are full of oil... so yeah more cleaning to consider. With the intake off you could also wash out the intake side from oil using the methods above with the plug out. I guess I would turn the engine to shut the valve, wash it really good, then turn the motor and move on to the next valve etc... but be sure the plug is out anyways the entire time and that you clear all cylinder with plugs out. Cant stress that enough.

Quiche2192 · 04-01-2019, 08:13 PM

Thanks for the advice! I was thinking the same thing about cleaning the whole pcv system and then running the engine and checking what gets fouled up with oil. I'll start with the leakdown test and work from there. Gonna do that this weekend (if I can manage to get all the parts for my steering rack rebuild).

I ordered a new pcv valve so I'll be changing that for sure.

Regarding that restrictor, I'm not quite sure where that is located. Is it between the T-fitting and the line going to the turbo? The thing is, I don't have a line going to the turbo for a vacuum. Mine just goes to atmosphere. So it basically just vents fumes based on positive crankcase pressure instead of sucking out the fumes through a vacuum. It's another thing I want to change by connecting a line from the T-fitting to the intake pipe between the MAF and the turbo.

I don't think the valve cover gasket is leaking. It didn't look like the plug bore is filled with oil. It looks more like the combustion chamber is.

Side note: I still can''t manage to upload images. It's a supported file type, under the upload limit, and I have enough space to upload media, but I keep getting an upload failed notification. I don't really mind, but I just wanted to share an image of my pcv routing.

Here's an imgur link to it: https://imgur.com/a/308jtam

Syrussilvia · 04-01-2019, 09:21 PM

If you're still having oil in the combustion chamber after you've cleaned the pcv hoses also look into replacing valve stem seals. If they degrade over time they will cause oil to leak into the combustion chamber, either at idle or after letting off throttle.

Kingtal0n · 04-02-2019, 05:52 AM

restrictor/pcv discussion link (we've had years of this stuff)

https://zilvia.net/f/showpost.php?p=...0&postcount=19

Kingtal0n · 04-02-2019, 05:52 AM

This is how you want it (factory)

jedi03 · 04-02-2019, 07:29 AM

mine (type x) had it between t and the block inside a hose....

Quiche2192 · 04-03-2019, 06:48 AM

Quote:

Originally Posted by Kingtal0n

restrictor/pcv discussion link (we've had years of this stuff)

https://zilvia.net/f/showpost.php?p=...0&postcount=19

Regarding that picture. That's the fitting on the intake that's connected to the T-fitting on the valve cover, right?

I don't have the stock intake and from what I've read, that brass fitting is a restrictor.

I want to weld in a fitting to my current intake pipe right before the turbo to connect the T-fitting to, so I can have a vacuum in the pcv line.

Do I need to put that restrictor? How do you do it with an aftermarket intake that doesn't come with a fitting for the PCV system?

jedi03 · 04-03-2019, 08:42 AM

i have one from another car with same sizing (i apologize i don't remember which one, but it fits in line with the hose to the intake...just find something that you can weld on that will have a hole at a similar size and should do the job!

03-31-2019, 12:08 PM	#1
Quiche2192 Join Date: Oct 2018 Location: FL Age: 32 Posts: 47 Trader Rating: (0) Feedback Score: 0 reviews	Burning oil My redtop has been burning oil only at idle and I've been going through some steps to try and fix it. But I thought I'd post about it here and see if anyone has some input for my specific case. First of all, I looked up everything I could find about the issue and I found that this is usually related to a failing turbo. I still have the T25, and I checked the play in the turbo which is the only test I have performed on the turbo so far. It has about 1-2 mm of end play which I think is too much. So turbo will probably be changed out. BUT I also wanted to check engine compression just to see where it's at right now and this is what has me stumped. I have 160 psi all around which is fine. But when I opened up cylinder 4, I found a lot of oil in the combustion chamber. I unscrewed the spark plug and it was covered in oil. There was so much oil that some spilled into the spark plug well. So this what I am having issues with. What is causing all this oil to end up in just the fourth combustion chamber? The compression seems fine. I realize that oil can help seal the rings, fooling you into thinking the chamber has more compression than it actually does, but is that likely? So what I wonder is, is the bad turbo causing the chamber to fill up with oil? I don't think that's likely. So then is it a bad pcv system? Mine's stock, but one part of the pcv system that I realized isn't quite ideal is that, from the t-fitting on the right side of the valve cover when looking at the engine from the front of the car, the line that is supposed to go to the intake pipe, right before the turbo, actually just has a small air filter on it. It's not connected to anything, it just goes to atmosphere through a filter. Could that be causing oil to pool up in the fourth cylinder? I can't seem to attach pics. I keeps saying upload of file failed... So the steps I want to take are: 1. Change the pcv valve 2. Connect the T-fitting to the intake pipe right before the turbo (does anyone know of any intake pipes that have a fitting for this?) I'll do this first and see how things go. If it still smokes after that but there's no oil in the combustion chamber, I can decide to replace the turbo. If there is oil, I'll need to rebuild. What I wanna ask is, does anyone have any tips on how to make this process a bit easier? Am I thinking wrong about any of this? How do you recommend I run the PCV system from the T-fitting? Is the PCV valve a known failure point? And does a bad PCV system let oil pool in the combustion chamber?

04-01-2019, 08:51 AM	#2
jedi03 Nissanaholic! Join Date: Jul 2008 Location: albuquerque Posts: 1,836 Trader Rating: (8) Feedback Score: 8 reviews	usually a bad valve seal will cause oil to puddle in there...sometimes a bad ring. A leakdown test will let you know more, sometimes rings stick (my STI had this was going through a quart every 1k miles) and i ran seafoam through the whole block and fuel system, ran ATF in my gas (~1/2 quart to one fill up) and did a few oil changes way before they were due and it nearly stopped all consumption (only have oil vapors going through intake and see it puddled in the manifold) if there is excess blowby, your PCV system may need to be modified or your rings are going, the good compression suggests otherwise. The oil you found, is it coming from the sparkplug tube down or from the piston up? If going down could be failing valve cover gasket.

04-01-2019, 01:34 PM	#3
Quiche2192 Join Date: Oct 2018 Location: FL Age: 32 Posts: 47 Trader Rating: (0) Feedback Score: 0 reviews	I'm gonna do a leakdown test next. But since you brought it up, I think it might be a bad valve seal or at least something to do with the valvetrain, cause it's in a less than ideal condition

04-01-2019, 03:57 PM	#5
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 41 Posts: 4,828 Trader Rating: (17) Feedback Score: 17 reviews	Your on the right track. Change the pcv valve. Take all the PCV hoses off the engine and wash them out with degreaser. That includes intake and turbo side pcv You may have the PCV routed incorrectly. Or a clogged restrictor. There is an OEM piece in the crankcase -> turbo inlet that sometimes gets clogged up with carbon deposits. take all the pre-turbo plumbing (rubber hose that holds air filter / maf) and wash it fully also. The basic idea is: Once you've cleaned all the hoses. You will be able to clearly see if any oil is actively getting into them once you re-run the engine. The cylinder full of oil: what I would do (do not do this if you are inexperienced) Take spark plug out and wash the cylinder with some kind of solvent. Maybe brake cleaner but there is probably something less drastic. In the past I've even used tap water and then turned the motor over by hand with the plugs out to remove the water. Followed by cranking without plugs to further remove the liquid. Then brake cleaner it and let is all evaporate to dry again before putting back the plug. Then put new plugs in it. With all that cleaned up, everything oil spotless, clean plug etc... Re-run the motor then check periodically for oil. Then do another compression test if you see no oil to get a real reading. Basically if the problem was in the pcv side, it will stay clean once you do all that. But if you have a broken piston ring the oil will instantly re-fill the cylinder/plug while all the pcv hoses stay clear and clean. The only warning here is that the intake manifold might also need cleaning. It could be holding alot of oil if the pcv is at fault, meaning it could simply re-supply the cylinder with oil. So you may also consider removing and degreasing the intake manifold along with all this other stuff. If you find the problem was in the PCV system then it also probably means the head ports are full of oil... so yeah more cleaning to consider. With the intake off you could also wash out the intake side from oil using the methods above with the plug out. I guess I would turn the engine to shut the valve, wash it really good, then turn the motor and move on to the next valve etc... but be sure the plug is out anyways the entire time and that you clear all cylinder with plugs out. Cant stress that enough.

04-01-2019, 08:13 PM	#6
Quiche2192 Join Date: Oct 2018 Location: FL Age: 32 Posts: 47 Trader Rating: (0) Feedback Score: 0 reviews	Thanks for the advice! I was thinking the same thing about cleaning the whole pcv system and then running the engine and checking what gets fouled up with oil. I'll start with the leakdown test and work from there. Gonna do that this weekend (if I can manage to get all the parts for my steering rack rebuild). I ordered a new pcv valve so I'll be changing that for sure. Regarding that restrictor, I'm not quite sure where that is located. Is it between the T-fitting and the line going to the turbo? The thing is, I don't have a line going to the turbo for a vacuum. Mine just goes to atmosphere. So it basically just vents fumes based on positive crankcase pressure instead of sucking out the fumes through a vacuum. It's another thing I want to change by connecting a line from the T-fitting to the intake pipe between the MAF and the turbo. I don't think the valve cover gasket is leaking. It didn't look like the plug bore is filled with oil. It looks more like the combustion chamber is. Side note: I still can''t manage to upload images. It's a supported file type, under the upload limit, and I have enough space to upload media, but I keep getting an upload failed notification. I don't really mind, but I just wanted to share an image of my pcv routing. Here's an imgur link to it: https://imgur.com/a/308jtam

04-01-2019, 09:21 PM	#7
Syrussilvia Leaky Injector Join Date: May 2018 Location: Westminster Age: 31 Posts: 78 Trader Rating: (0) Feedback Score: 0 reviews	If you're still having oil in the combustion chamber after you've cleaned the pcv hoses also look into replacing valve stem seals. If they degrade over time they will cause oil to leak into the combustion chamber, either at idle or after letting off throttle.

04-02-2019, 05:52 AM	#8
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 41 Posts: 4,828 Trader Rating: (17) Feedback Score: 17 reviews	restrictor/pcv discussion link (we've had years of this stuff) https://zilvia.net/f/showpost.php?p=...0&postcount=19

04-02-2019, 07:29 AM	#10
jedi03 Nissanaholic! Join Date: Jul 2008 Location: albuquerque Posts: 1,836 Trader Rating: (8) Feedback Score: 8 reviews	mine (type x) had it between t and the block inside a hose....

04-03-2019, 08:42 AM	#12
jedi03 Nissanaholic! Join Date: Jul 2008 Location: albuquerque Posts: 1,836 Trader Rating: (8) Feedback Score: 8 reviews	i have one from another car with same sizing (i apologize i don't remember which one, but it fits in line with the hose to the intake...just find something that you can weld on that will have a hole at a similar size and should do the job!