2001 QX4, 136k Depressed/Concerned about Oil loss. Looking for help in troubleshooting

[Legend11]

Hello,

Just to give some history on my truck... I purchased it back in July 2014 with 123k; it currently has 136k on it (I bought from a private dealer; I'm the 4th owner). When I purchased my truck, I noticed the oil was a little over a quart low when i checked it. This should have been a redflag to me, but I thought nothing of it at time unfortunately. Also, it was worth noting that my truck has had a loud rattle on most cold starts that goes away after a few seconds (timing chain noise?) that I have dealt with - it drives fine and sounds great otherwise.

Since I've had it, I immediately switched to to Mobil 1 5W30 High Mileage oil to try to help the rattle. I replaced the Oil Cooler due to a leak a year ago but it hasn't helped. I seem to be losing 2-2.5 quarts every 3,000 miles with no leaks in my driveway ! After searching the forum, should my next move be to check the Power Valve screws and switch back to Conventional? I already purchased the gaskets for the Power Valve screw job, spark plugs, and new PCV Valve (oem); just depressed on what I find when i get to the screws...

Within the past month, I have spent a lot of money putting some work in my truck: new windshield, new front brake and rotors, transmission pan drop/refill, coolant flush, brand new tires (just bought!), but now I'm suddenly becoming concerned about the current status of my engine and if it's worth pursuing. Hoping to have my nerves calmed a bit and to come up with a reasonable strategy to fix this.

I'm just a little bummed that I may have a serious engine issue. I really am kicking myself now...

Thank you for any help.

[yeldogt]

Not sure how the power valves would affect the oil usage.

All of my Pathfinders (3x 2002) used some oil -- even the current one at 85k. I run conventional high mile oil in mine 5W/30. For whatever reason all of mine would drip a bit with the Synthetic -- I normally get the Castrol (on sale). I make a habit to check mine and add 1/2 qt when needed to keep it full.

You can always do a compression test -- Check the rings. And ..... I would have someone knowledgable listen to the noise .... not for the oil loss .. just to make sure it's not in the chains.

Personally -- I would live with the oil loss.

[saskapath]

I too have a Pathfinder of that era that uses a LOT of oil. I've just been living with it, checking it often and adding jugs of oil as needed. I have noticed that changing to 10-30 conventional oil has helped somewhat but it certainly didn't cure the issue. The things I've seen here and in other forums that you might want to look at include:

Change the PCV valve. I don't think this is a terribly difficult job but you do have to remove the intake manifold to get at it. It's first on my list of jobs when I have some time.

Power valve screws. As noted in many posts, if you find a missing screw it's probably been ingested and who knows what damage that has caused. Mine has a manual transmission so I've ruled this one out.

Plugged baffle drain holes in the PCV side valve cover. Causes oil to be ingested via the PCV valve into the intake. I'm planning to install an oil catch can in this line to see how much oil is entering the combustion stream here.

Debris from the cats being sucked back into the engine and causing wear on rings and valves. Probably not much you can do about it if this is your problem.

Unfortunately the copious amounts of oil passing through the engine have killed both my cats, but there is no point in doing anything about that till the oil issue is fixed. Otherwise mine runs like a top, no noise, decent fuel consumption for a Pathfinder, etc.

Good luck and keep us posted on what you find.

[atraudes]

What they said Definitely check out the power valves first; like you said, if you find bad news there, there may be no point in continuing.

As for the timing chain rattle, there is a common issue with the VQ35DE engines where the timing chain guides wear down and the adjusters eventually max out, allowing the chain too much flexibility and eventually allowing it to slap against the timing chain cover. You can let it go and live with it, but eventually it will get so bad it'll start happening at idle and acceleration. I've heard of the issue in G35's, Quests, Altimas, etc. This thread has the best information I've found on the topic so far. You should be able to use the information you find there to see if it's what you're experiencing and how to fix it.

As for oil, I'd second the other recommendations and suggest you get a Castrol 10w-30. I've done a bunch of reading on what the best oil is for these engines and Castrol is highly recommended, in addition to using something heavier like 10W-30. Oddly enough Mobil 1 generally doesn't agree with it Check out this thread for some good linked reads.