VG30E oil burning

[Steve Niece]

So, we've got a 1995 Pathfinder XE V6 with 180,000km on it, and it burns
oil like crazy (approx 1 litre per 500 km!). The trick is, that it only
seems to burn oil on the highway, when the engine is good and warm.
There's no blowby, the PCV valve and intake are clean as a whistle. I
can do the trick where you step on the gas, and then back off, expecting
to see blue smoke that's come by the valve seals...nothing. In fact,
there's no evidence of blue smoke in any sort of normal city driving.

So, I'm wondering if perhaps the catalytic converter is plugged, and
it's causing the engine to overheat, causing the oil to burn off. When
I checked the oil on a recent long trip, it always seemed to be quite
dark when I topped it up, even when I had only changed it with fresh
5-600km ago. The coolant temperature seems good most of the time
(approx. 1/3 of full scale, occasionally higher) Does my assumption of
the catalytic seem like a reasonable one? Any other thoughts which may
help me track this down? I understand that it isn't a particularly easy
thing to check, but may be worth a try, considering the truck is almost
10 years old?

Any help is greatly appreciated.
Thanks,
Stephen

[Steve T]

Post by Steve Niece
So, we've got a 1995 Pathfinder XE V6 with 180,000km on it, and it burns
oil like crazy (approx 1 litre per 500 km!). The trick is, that it only
seems to burn oil on the highway, when the engine is good and warm.
There's no blowby, the PCV valve and intake are clean as a whistle. I
can do the trick where you step on the gas, and then back off, expecting
to see blue smoke that's come by the valve seals...nothing.

I've never seen a nissan burn oil because of valve stem seals.

Post by Steve Niece
So, I'm wondering if perhaps the catalytic converter is plugged, and
it's causing the engine to overheat, causing the oil to burn off.

Sorry but your dreaming. Sounds like the oil control rings are stuck to the
pistons. Only cure is a bottom end rebuild. It's posible the rod bearing
are worn out causing/contributing to this but not likely. How much rattling
does it do on a cold start up?

[NissTech]

You state that the engine is using/burning oil.

The only thing I get out of this post is that the engine has an oil
rentition problem


What diagnosis have you done to confirm the engine is burning it...

does it smoke ?
what do the spark plugs look like ?
are there any external leaks ?

Nissan engines do not have an oil consumption problem unless you give it a
reason to, like not changing the oil, overheating the engine , etc..


My guess is the engine has a severe oil leak. have you gotten under it to
look?

higher mileage/age pathpuppies develop a rear main seal leak.

Post by Steve Niece
So, we've got a 1995 Pathfinder XE V6 with 180,000km on it, and it burns
oil like crazy (approx 1 litre per 500 km!). The trick is, that it only
seems to burn oil on the highway, when the engine is good and warm.
There's no blowby, the PCV valve and intake are clean as a whistle. I
can do the trick where you step on the gas, and then back off, expecting
to see blue smoke that's come by the valve seals...nothing. In fact,
there's no evidence of blue smoke in any sort of normal city driving.
So, I'm wondering if perhaps the catalytic converter is plugged, and
it's causing the engine to overheat, causing the oil to burn off. When
I checked the oil on a recent long trip, it always seemed to be quite
dark when I topped it up, even when I had only changed it with fresh
5-600km ago. The coolant temperature seems good most of the time
(approx. 1/3 of full scale, occasionally higher) Does my assumption of
the catalytic seem like a reasonable one? Any other thoughts which may
help me track this down? I understand that it isn't a particularly easy
thing to check, but may be worth a try, considering the truck is almost
10 years old?
Any help is greatly appreciated.
Thanks,
Stephen

[Steve T]

Post by NissTech
You state that the engine is using/burning oil.
The only thing I get out of this post is that the engine has an oil
rentition problem
What diagnosis have you done to confirm the engine is burning it...
does it smoke ?

Not a good diagnosis tool on a car with a converter..

Could be a bad leak as you said. I assumed someone would look for puddles of
oil under their car first. Most people say to us "My car has an oil leak"
when they start using oil as they don't want to think it's burning oil,
they know that isn't cheap to fix! :-)

[Steve Niece]

Sorry, I guess I should have clarified this part first. Nope, no leaks
whatsoever. The only time there's oil underneath, is just after a
change due to the dumba place they put the oil filter. The pilot
bearing was changed when we got it, and while the transmission was
separated, the rear seal was changed. No smoke that I can see, and
certainly not what I'd expect when consuming this much oil. I haven't
checked the plugs recently, but they seemed relatively clean when I
changed them about 5000km ago (just after purchasing the truck)

Thanks,
Stephen

Post by NissTech
You state that the engine is using/burning oil.
The only thing I get out of this post is that the engine has an oil
rentition problem
What diagnosis have you done to confirm the engine is burning it...
does it smoke ?
what do the spark plugs look like ?
are there any external leaks ?
Nissan engines do not have an oil consumption problem unless you give it a
reason to, like not changing the oil, overheating the engine , etc..
My guess is the engine has a severe oil leak. have you gotten under it to
look?
higher mileage/age pathpuppies develop a rear main seal leak.

Post by Steve Niece
So, we've got a 1995 Pathfinder XE V6 with 180,000km on it, and it burns
oil like crazy (approx 1 litre per 500 km!). The trick is, that it only
seems to burn oil on the highway, when the engine is good and warm.
There's no blowby, the PCV valve and intake are clean as a whistle. I
can do the trick where you step on the gas, and then back off, expecting
to see blue smoke that's come by the valve seals...nothing. In fact,
there's no evidence of blue smoke in any sort of normal city driving.
So, I'm wondering if perhaps the catalytic converter is plugged, and
it's causing the engine to overheat, causing the oil to burn off. When
I checked the oil on a recent long trip, it always seemed to be quite
dark when I topped it up, even when I had only changed it with fresh
5-600km ago. The coolant temperature seems good most of the time
(approx. 1/3 of full scale, occasionally higher) Does my assumption of
the catalytic seem like a reasonable one? Any other thoughts which may
help me track this down? I understand that it isn't a particularly easy
thing to check, but may be worth a try, considering the truck is almost
10 years old?
Any help is greatly appreciated.
Thanks,
Stephen

[Steve T]

Post by Steve Niece
Sorry, I guess I should have clarified this part first. Nope, no leaks
whatsoever. The only time there's oil underneath, is just after a
change due to the dumba place they put the oil filter. The pilot
bearing was changed when we got it, and while the transmission was
separated, the rear seal was changed. No smoke that I can see, and
certainly not what I'd expect when consuming this much oil.

Like I posted, you won't see the smoke on a car with a converter that works.

Try this, when it's cold rev it hard a few times and looks for blue smoke.
If you see it, the oil control rings are stuck. A final diagnosis could be
done with a scope looking at the tops of the pistons through the plug hole
(The edges of the piston will be washed clean) but that isn't a tool many
people have.

[Steve Niece]

I've tried the reving thing on a few occasions, with no smoke to be
seen. I may actually be able to come up with a borescope to check the
pistons, thanks for the tip. I suppose I could also disconnect the
converter, and try reving it to look for smoke as well if there's
concern that the smoke isn't making it through the cat. (and then
apologize to my neighbours) :)

Steve

Post by Steve T

Post by Steve Niece
Sorry, I guess I should have clarified this part first. Nope, no leaks
whatsoever. The only time there's oil underneath, is just after a
change due to the dumba place they put the oil filter. The pilot
bearing was changed when we got it, and while the transmission was
separated, the rear seal was changed. No smoke that I can see, and
certainly not what I'd expect when consuming this much oil.

Like I posted, you won't see the smoke on a car with a converter that works.
Try this, when it's cold rev it hard a few times and looks for blue smoke.
If you see it, the oil control rings are stuck. A final diagnosis could be
done with a scope looking at the tops of the pistons through the plug hole
(The edges of the piston will be washed clean) but that isn't a tool many
people have.

[Steve T]

Post by Steve Niece
I've tried the reving thing on a few occasions, with no smoke to be
seen.

Well it's either leaking it or it's burning it!

Like I said I've never seen valve stem seals fix one of those engines. I've
had several customers come in and basically demand they be replaced, even
after warning them it wasn't going to fix it, of course they knew
better! :-) Every one ending up needing rings.

[Steve Niece]

It just seems curious that I can drive around town (short trips), go
through a tank of gas, and the oil level barely wavers. Once on the
highway though, 1 tank of gas equals 1 litre of oil. I'm grasping at
straws, admittedly, but would a ring problem exhibit these sorts of
conditions?

Thanks,
Stephen

Post by Steve T

Post by Steve Niece
I've tried the reving thing on a few occasions, with no smoke to be
seen.

Well it's either leaking it or it's burning it!
Like I said I've never seen valve stem seals fix one of those engines. I've
had several customers come in and basically demand they be replaced, even
after warning them it wasn't going to fix it, of course they knew
better! :-) Every one ending up needing rings.

[Steve T]

Post by Steve Niece
It just seems curious that I can drive around town (short trips), go
through a tank of gas, and the oil level barely wavers. Once on the
highway though, 1 tank of gas equals 1 litre of oil. I'm grasping at
straws, admittedly, but would a ring problem exhibit these sorts of
conditions?

Yep, -if- it was valve seals, stop and go would use more oil than highway.
More load/rpm makes oil go by the rings more.