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VQ35 excess oil consumption - Is it terminal?


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So first off, yes I know there's another post on this topic but I wanted to start a separate one because my question is a bit different from the other one posted.

 

In a nutshell, I bought a 2002 R50 Pathfinder in September to use as a Daily Driver (DD.) My "road trip" vehicle is a 2004 Suburban that I use to pull a 16' travel trailer when we go on long camping trips.

 

I have to admit I've been admiring the R50 Pathfinder ever since they did the "facelift" in about 1999 or 2000 to raise the center of the grill a bit (I didn't really care for the 1996 - 99 front end.) Over the last few years I've noticed R50 Pathfinders everywhere! They're very common here in Colorado (Denver area.)

 

Since I like to shift my own gears and the Suburban doesn't give me that option, I started searching for a Pathfinder with a 5 speed. I was fortunate (I thought!) to find one in absolutely cherry condition, an SE 4x4 with the 5 speed in great condition and only 117k miles on it! Bought it in September and absolutely love it. I replaced the crap Kumho tires with some decent Cooper M+S and it does awesomely in the snow.

 

Except for a few "rub marks" on the bumpers, this Pathy doesn't have a scratch or dent on it, and everything works perfectly. It's comfortable, fun to drive and handles well. It's just a great little truck!

 

But...a few weeks after I bought it, I filled with gas and went to check the oil. Dipstick was bone dry! I thought "maybe there's a trick, maybe I need to let it sit for a few minutes, maybe it has a short dipstick" etc. Checked again -still dry, so I added a quart, and it was now showing full on the dipstick.

 

No problem - I figured maybe it just needed to be topped off. Drove for a few more months, usually when I filled with gas I didn't bother to check the oil. But just for the hell of it, I checked it in January. Dipstick was bone dry, again. Now I was getting concerned. So I topped it off, drove for a while, then a few weeks ago a CEL came on. I have a Scangauge II on my Suburban but I don't (yet) have a code reader or re-setter on the Pathy, but the previous owner told me sometimes the CEL would come on. I've had other vehicles do that and its usually something minor, a sensor or something, so I ignored it and continued to drive.

 

Last week I filled the tank, and checked the oil. BONE DRY DIPSTICK! :headwall:

 

Got some oil, it took 2 full quarts to fill up, but now it shows as "full" on the dipstick. Oh, and here's something funny: When I got back in and started the engine, the CEL was off!

 

Now, before anyone asks: No, it is NOT leaking. Not so much as a drop of oil has hit the ground from this truck. We just moved into a new house (new to us) and my wife is very picky about keeping the house clean - if my truck had dripped oil, I would have heard an earful from her, but not a peep.

 

And there's no evidence of burning, either. I've owned vehicles that burned oil. My 1990 Montero with the 3.0 V6 had a notorious valve guide issue that caused it to burn a quart every 1000 miles. It would put out visible blue smoke when idling. And I had a 1997 Protégé sedan that had bad rings (to be fair the engine had 210,000 miles on it!) and that used to leave a huge cloud of blue smoke every time I started it.

 

But the Pathy? nothing. No smoke, no smell. My engine seems to be a "Bermuda Triangle" of oil. It disappears, but I don't know where. Now common sense tells me that oil doesn't just 'disappear', if it's not leaking, it has to be burning. Maybe the emission control equipment is so good it scrubs the exhaust clean of oil smoke, I don't know.

 

After the last incident, I did some googling, and that was when I discovered a well documented, but still unexplained, loss of oil in the VQ35 engines. The odd thing was that there seemed to be no actual consensus of what was causing it . Some said a bad piston ring, some said it had something to do with the catalytic converters sucking oil out of the engine (how does that even work? The Cat should be connected to the exhaust manifold which is connected to the exhaust valves. Shouldn't the engine oil be BELOW the piston rings and separate from the exhaust valves?) I've even heard some say it has something to do with the PCV valve.

 

And just as there is no consensus on the cause, there's no consensus on the fix. In fact, there doesn't seem to be a fix, at least not that I can tell.

 

So, with that long preamble, my question is simply this: In the opinions of those here, does my excess oil consumption mean that my engine is destined to fail sooner rather than later? I'm trying to figure out if it makes sense to keep the Pathy or to cut my losses and get rid of it.

 

The oil itself is not an issue to me - if my excess oil consumption just means I need to carry a couple of quarts in the car and fill up as needed, I'm fine with that.

 

But my concern is that I'm hearing that the excess oil consumption is actually a symptom of a very serious condition that will lead to engine failure and that this may not be too far off. Worse yet, the only "cure" would be to drop another engine in (which I'm assuming would be a $2500 - $3500 cost) and there would be no guarantee that the new engine wouldn't suffer the same fate, since it seems the excess oil consumption is just something that some engines have and some engines don't have, with no way of knowing which is which.

 

A secondary question would be: If the excess oil consumption is a symptom of a serious problem, then how can I expect that problem to manifest itself in the future? IOW what is the sign of impending failure?

 

As I said, I love this little Pathfinder, but if its days are numbered I'd rather get rid of it now, before the engine craps out on me.

 

Anyway, thanks for reading this long message, I'd appreciate any input that anyone can put in.

Edited by Martinjmpr
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In my experience with engines with significant oil loss it can really only be 2 options:

 

1) Leaking out. Either onto the ground or into the water.

2) Burning it.

 

I would suggest pulling the spark plugs and see what they look like. If it is burning that much it should show on the plugs.

 

As for the engine replacement if you are handy with tools you can do it yourself in a day or two.

If you live in a larger metropolitan area you can likely find a good low mileage motor from a salvage yard with a short warranty for less than $1000. Try to make sure the one you get it from was salvaged because of an accident (preferably not a front end one). If you don't signs of damage on the vehicle then it was likely salvaged because of mechanical failure (which you don't really want to find out about the hard way after spending all the time installing it).

Search over here and see what engines pop up in your area:

http://car-part.com

 

I personally would take a low mileage salvage yard motor over a rebuilt one.

The re-builders usually don't care about the tolerances much when they rebuild one. They just get it somewhere close and leave it at that.

The factory ones will have very good tolerances.

Edited by Blindaviator
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If you pull the plugs refer to this chart to read them:

https://www.ngksparkplugs.com/about-ngk/faqs/spark-plug-faqs/how-do-i-read-a-spark-plug

 

You might also try a compression test while you have the plugs out. Although the compression will only tell you if there is an issue with rings. Compare the compression values with OEM tolerances. If one or more cylinders are too far outside the specs then you have to assume ring issues.

 

If you have a laptop You could also pick up a cheap USB "Endoscope" or "Borescope" and look down into the cylinders for any visible issues.

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Not an uncommon complaint with the 3.5. My dad's '03 used a quart every thousand miles but only smoked on warm starts. He took to running synthetic oil, not to slow the burning, but because the smoke it made was less visible. I read a few theories at the time, including that the PCV could somehow siphon oil out (changing that didn't help). The catalyst theory sounds like a garbled version of what happened with the QR series motors in the Sentras. Apparently their cats were mounted too close to the engine, got too hot, and fell apart inside, and the EGR on those worked by holding the exhaust valve open to suck exhaust back into the cylinder... along with bits of the disintegrating cat, with predictable results. I haven't heard of anyone proving a similar issue with the VQ. They do have power valve screws that have been known to work loose and fall in, but IIRC only the auto trans rigs got those. Bad valve seals sounded most likely to me but I never got to tear the POS apart and find out.

But apart from sucking back a quart a week, and a (likely unrelated) issue with something on the swirl valve circuit making the drive-by-wire act up, it ran fine. Pulled hard, fuel economy was normal, no unusual codes. The dealer suggested that it would probably keep running just fine so long as he kept adding oil. I would expect the oil in the exhaust to kill the catalysts eventually, but so long as you don't let it run dry, I wouldn't expect the engine itself to fail.

 

If you're looking at secondhand engines, check compression. My dad considered an engine transplant and discovered that the VQs in the local yards all had an unusually large variance in compression from one cylinder to another.

Edited by Slartibartfast
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Thanks for all the input. I think I may have overreacted when I first started reading this stuff on the internet - I sometimes have to remind myself that for every person who posts up a message that says "my vehicle is a POS!" there are 20,000 people driving that same make and model who don't post on the internet because there are no problems.

 

At this point I'm going to say "no harm/no foul." Truck runs fine, MPG is right about where it should be (16.5 - 17.5 in mixed city driving), power is good, no smoking, hesitating, backfiring, no CEL (anymore). I'll get in the habit of checking the oil every 150 miles or so and if it needs to be topped off, I'll top it off. Otherwise I won't worry.

 

As I said, this is mostly an around-town or around-the-region vehicle, long trips will be in my Suburban. I seem to last about 2 1/2 - 3 years on a daily driver before I get bored and want something else. It would be nice to have something that got better mileage - my previous DD was a 1996 Mazda B2300 pickup (aka Ford Ranger.) That little truck was slow as hell and not particularly "fun" to drive but it got 22 - 25 MPG on a regular basis. But it was also 2wd which meant that if snow or ice was in the forecast I'd leave it at home and drive the big gas guzzling Suburban. Now that I have a DD with 4wd and good tires I don't worry about getting caught in a snowstorm so that - and the fact that the Pathy is more comfortable, more powerful, and more fun to drive - makes up for the slight decrease in MPG.

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Something else I was thinking about after my last reply... It is possible it is leaking out but only at highway speeds / under load & when you come to a stop the leak stops...

 

One place to look (I just learned this yesterday) is the oil cooler... I didn't even know these trucks had one until I was doing some research...

Apparently they are prone to leaking quite often... They have 2 O'rings that you can replace pretty easily and stop the leak (I will be doing this soon as I'm sure mine is likely leaking after 215k miles)...

If the oil cooler is leaking it will likely not drip on the ground much as it's right beside the oil filter above the plastic brush guard... It would prolly only leak under higher pressures (highway speeds) where the oil would be blown to the rear of the vehicle by wind and not show on the ground when you stopped...

 

Pictures with a how to I found over here:

http://www.nissanforums.com/pathfinder/142468-2001-pathfinder-odd-oil-leak-pics.html

Edited by Blindaviator
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You're probably right about that leaking under load. I know mine is wet, but I never see a spot on my driveway or at work. I know some people have just tightened it and that fixed their problems. The parts are cheap enough and if you can change an oil filter, you can change the seals on the oil cooler.

 

I've owned an RX7 so im no stranger to adding oil. I just buy 2 5 quart jugs and add as needed. I have about 3.5 quarts left in the second jug with 1500 miles to go until I change my oil.

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Hmmm...Leaking only at highway speeds? Interesting, I hadn't really considered that, but then again I haven't gotten onto the creeper to look underneath either. If it was just leaking at highway speeds, wouldn't there at least be enough oil on the frame to drip down after I parked though? I have to emphasize I am dripping absolutely nothing!

 

Still, if this was the case it would set my mind at ease that my truck was headed for a breakdown. As long as I keep the oil topped off, I should be OK until I can track down what is happening. That would also explain why it doesn't seem to be burning oil, no visible smoke, etc. My old Montero used to burn a quart every 1000 miles (which is half of what I'm losing) and had a noticeable blue cloud of smoke, especially when starting up!

 

 

Edited by Martinjmpr
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It is my understanding these trucks have cat's and resonator as well as a muffler (I haven't really checked that myself)... It could be that there is so much interference that the oil smoke doesn't make it out...

I have seen others posting that they have unexplained oil loss and no idea where it goes so your not alone...

 

I have had cars in the past that would only lose oil at highway speeds and leave no visible signs of it so it is possible... It would spread the oil across the bottom of the vehicle and any accumulations would be blown away before it could have enough to drip.

Usually a sign of it would be an oil streak on the bottom of the vehicle...

 

Basically I am just guessing here of course... I would personally pull a spark plug or two (several are quite easy to reach) and see what they look like.. That is the quickest way to tell if it is burning it...

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I got a 5-speed '02 a couple of years ago which has consumed oil at the constant rate of 750mi/qt since I bought it. No smoke, no drip---who knows where it goes? The engine is strong and quiet with no signs of power loss. So I have dumped in 20 quarts or so at, what, $3, so $60 so far. It's worth it for a rugged bargain vehicle and it adds one more piece of evidence that the world is a mystery.

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Well, I just checked it at 200 miles after the last top-off and it is still showing full of oil, so I'll be cautiously optimistic.

 

What I'd like to be able to figure out is under what circumstances is the oil burning. The Pathy is my DD so it's normally going on about a 20 mile (round trip) daily commute plus typical stop-and-go city driving. Occasionally, I'll take it on a longer trip, so I want to see whether it's the stop-and-go or the long drives that causes it to burn more oil - that could be a clue as to what the problem is.

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  • 2 weeks later...

Oil cooler on the VQ35 manual transmissions??? Thought that was only the automatic versions.

 

Sent from my SAMSUNG-SM-G900A using Tapatalk

 

The oil cooler is on the engine, attached to the oil pan. It is a water to oil cooler. Water from the radiator gets into this little donut , that carries oil from the oil pan to cool it and then return to the engine. It have 3 seals and they become crackers and start leaking. That oil cooler gets all black covered in oil and just looks like part of the oil pan but is not. When you clean it is shiny aluminum color. When it leaks is slow and the oil gets right into the front engine cross member and goes down the whole frame, making it less traceable. There is also a trasmission cooler inside the water radiator. It is a tube that just goes thru the lower part of the radiator. When it leaks internally, it mixes water with your transmission fluid and kills the transmission, specially in the 2005 and newer models. The engine oil cooler is in both auto and manual. The transmission cooler I think is only on the auto. Hope this helps.

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Well, I just checked it at 200 miles after the last top-off and it is still showing full of oil, so I'll be cautiously optimistic.

 

What I'd like to be able to figure out is under what circumstances is the oil burning. The Pathy is my DD so it's normally going on about a 20 mile (round trip) daily commute plus typical stop-and-go city driving. Occasionally, I'll take it on a longer trip, so I want to see whether it's the stop-and-go or the long drives that causes it to burn more oil - that could be a clue as to what the problem is.

 

Do a compression check as others have suggested. I read somewhere of a few cases of engine sludge.If this has happened, your piston rings will stick and probably let oil pass thru them in a certain position. Your oil will burn slowly if it is in only a few cylinders. You could do some sort of internal cleaning. There are several ways, from seafoam to using a quart of transmission oil on you engine oil to using diesel instead of oil and doing a 20 minute run and then flush. If your pistons sludge get unclogged you might solve your problem. Also the oil cooler next to the oil pan leaks unto the front crossmember and goes to the frame before dripping to the ground so you might have all of your truck covered in oil underneath and not a drop in the floor. I have cleaned several engines with both mechanical and liquid flushes and they have not only survived but eliminated the missing oil problem. Also check if your engine is breating properly and the crankcase gases are exiting properly, which many times create the sludge when they dont get exhausted.

 

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Do a compression check as others have suggested. I read somewhere of a few cases of engine sludge.If this has happened, your piston rings will stick and probably let oil pass thru them in a certain position. Your oil will burn slowly if it is in only a few cylinders. You could do some sort of internal cleaning. There are several ways, from seafoam to using a quart of transmission oil on you engine oil to using diesel instead of oil and doing a 20 minute run and then flush. If your pistons sludge get unclogged you might solve your problem. Also the oil cooler next to the oil pan leaks unto the front crossmember and goes to the frame before dripping to the ground so you might have all of your truck covered in oil underneath and not a drop in the floor. I have cleaned several engines with both mechanical and liquid flushes and they have not only survived but eliminated the missing oil problem. Also check if your engine is breating properly and the crankcase gases are exiting properly, which many times create the sludge when they dont get exhausted.

 

I have a little trouble with missing oil.

 

I've been running synthetic oil for 100k miles. Is engine sludge as likely to develop when running synthetic this long, and I should try seafoam in the oil still? Just wondering since I thought prevention of sludge buildup was one of its advantages.

 

I've already had the valve cover gaskets replaced and that fixed about half of the missing oil.

 

Sent from my Nexus 5X using Tapatalk

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The oil cooler is on the engine, attached to the oil pan. It is a water to oil cooler. Water from the radiator gets into this little donut , that carries oil from the oil pan to cool it and then return to the engine. It have 3 seals and they become crackers and start leaking. That oil cooler gets all black covered in oil and just looks like part of the oil pan but is not. When you clean it is shiny aluminum color. When it leaks is slow and the oil gets right into the front engine cross member and goes down the whole frame, making it less traceable. There is also a trasmission cooler inside the water radiator. It is a tube that just goes thru the lower part of the radiator. When it leaks internally, it mixes water with your transmission fluid and kills the transmission, specially in the 2005 and newer models. The engine oil cooler is in both auto and manual. The transmission cooler I think is only on the auto. Hope this helps.

Thanks for the very detailed description. I'll look for it on my manual PF. How hard are those seals to replace as a DIYer?

 

The burning oil smell has dramatically reduced since my valve cover gasket replacement. But after 2 engine washes, I still smell a hint of burning oil. Hoping I can track that down.

 

Sent from my Nexus 5X using Tapatalk

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I have a little trouble with missing oil.

 

I've been running synthetic oil for 100k miles. Is engine sludge as likely to develop when running synthetic this long, and I should try seafoam in the oil still? Just wondering since I thought prevention of sludge buildup was one of its advantages.

 

I've already had the valve cover gaskets replaced and that fixed about half of the missing oil.

 

Sent from my Nexus 5X using Tapatalk

 

Well, synthetic helps up to a point. But if the sludge have reached the piston rings, it is kind of harder to remove from them and will take a few flushes to clean it completely. I think you should still try the seafoam or any of the other flushes I mentioned if you still have missing oil. Seafoam is the milder and safer flush. If you are not inclined to do a full engine swap I would not recommend to do the full diesel fuel flush. I have done that when I was willing and able to do and engine change if that failed. The automatic transmission oil mixed with regular oil flush is also milder and could be done relatively safely. Take in mind that any flush have the capacity of dislodging sludge material that could block something else(like an internal oil passage), so that is why with flushes you should go slow, take your time and do it several times at certain intervals. You should also download the manual for your vehicle and check the part about crankcase gases ventilation and check that all those lines are not blocked. In other cars(like toyota corolla), I have found that when the vent of the crankcase get clogged with sludge, those gases stay in the engine and cook the oil(aluminum is a heat sponge), then that cooked oil is what becomes sludge. Have you even used frying oil a few times and it starts becoming black and then solidify in chunks??? That is exactly what happens inside your engine when the crancase can not breathe this gases out. It becomes an oil pressure cooker and something have to give. I keep mentioning the compression test because that will tell you if your piston rings are worn out to the point of leaking, in which case there is nothing more to do but to measure the cylinders and install oversized rings. You could relatively easy remove the heads, measure the cylinders , do a light honing with a drill and attachment and reinstall bigger rings without touching the crankcase area. Assuming of course there is nothing wrong with your crankcase bearings.

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Thanks for the very detailed description. I'll look for it on my manual PF. How hard are those seals to replace as a DIYer?

 

The burning oil smell has dramatically reduced since my valve cover gasket replacement. But after 2 engine washes, I still smell a hint of burning oil. Hoping I can track that down.

 

Sent from my Nexus 5X using Tapatalk

 

Well, for me it was easy because I removed the oil pan(which involves removing the transmission and almost all the front suspension) and I removed the seals with the pan out. I had read of people changing them in site. It is difficult due to the small space but is not impossible. It have a main bolt running thru it, then 3 additional allen bolts(2 outside and one inside once you remove the main bolt.) You need the service manual for this to properly appreciate where the bolts are. You have to drain your radiator first because when you disconnect the 2 lines it will rain on you. Your smell of burning oil can be because of this, because as long as it is slowly leaking , it will go thru your frame and end up at some point getting to your exhaust and it will burn there. I dont know what tools you have available so it will all depend on that and your patience and skill to dedicate 1-3 hours to it. I think it is worth the time and you will eliminate another leak.There are 3 seals to change. One that goes to the base, one big o-ring and a smaller one. Ill try to find an illustration to post for you.

 

Edited by Qctech
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bad design of the oil baffle inside the valve cover that lets oil get suck through the pcv valve. go look at the pcv hose that connects from valve cover and plastic intake. @!*% is always wet.

Edited by deltaR50
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its the same exact problem with other nissan cars equipped with vq with yrs 01-04. nissan never acknowledge it. they all have that "mysterious" oil disappearing problem

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I rechecked mine. It is totally doable without removing anything else and will just take your time and to have all the gasket (1) and o-rings(2) available. Empty the radiator and lines. Loose both lines completely at the oil cooler, then take the main center bolt out. You can them pull the oil cooler out. Once you do that and remove the oil cooler , there are 2 allen type bolts out side and one inside that you have to remove to get the base out and change the rear gasket. Clean , put the gasket and o-ring and reinstall. Torque as per the manual, reconnect the lines, put coolant in your radiator and you should be good to go. You should be able to do it in one hour, 3 hours max.

 

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My 2003 also burns oil, about 1 quart every 1500 miles.

I've read a lot and in my case there are 3 possibilities:

1. Power valve screw(s) fell off and scratched the cylinder walls

2. PCV valve is bad

3. Driver side valve cover oil passage is clogged.

If I had time and did not use this car as a main vehicle in my family I would definitely tear down the engine and look at power valve screws and replaced the right valve cover while I'm at it.

I'm sure it would decrease the consumption.

But I have another question, probably silly one:

I'm using Mobil 1 Extended Performance with M1-108 filter and usually change my oil at 4000 miles and 6 months. I know EP oil is overkill but it's only 25$ at Walmart.

Because I'm using such a quality oil with good filter and change it very early, is there a chance that it will clean up the clogged passage in the valve cover? (If this is the cause of oil consumption)

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I doubt it. It's probably caked in there really bad if that is the issue. And, correct me on this if I'm wrong, but I don't believe oil flows through there, only vapor, so it's the leftover sludge crap that causes the clogging in the first place.

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I bought her in 2008 with 44k miles on it, now it has 98k miles. I use only synthetic oil and change it usually every 4-5k miles.

Is it a bad design or bad maintenance from previous owner?

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