VG30E oil burning

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

Reply to
Steve Niece
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I've never seen a nissan burn oil because of valve stem seals.

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?

Reply to
Steve T

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.

Reply to
NissTech

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! :-)

Reply to
Steve T

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

NissTech wrote:

Reply to
Steve Niece

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.

Reply to
Steve T

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

Steve T wrote:

Reply to
Steve Niece

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.

Reply to
Steve T

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

Steve T wrote:

Reply to
Steve Niece

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.

Reply to
Steve T

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