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06 PF - Low oil press at idle, plus whine Forums > > 06 PF - Low oil press at idle, plus whine 06 PF - Low oil press at idle, plus whine
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Old 08-27-2020, 05:48 AM
kphoger kphoger is offline
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2006 Pathfinder
 
Join Date: Aug 2020
Location: Wichita, KS
Posts: 3
Default 06 PF - Low oil press at idle, plus whine

2006 Nissan Pathfinder SE
Bought used - Sept 2016 - 118k miles
Symptoms began - Feb 2020 - 210k miles
Current mileage - Aug 2020 - 218k miles
Oil used - 5W30 non-synthetic
Symptoms affected by oil level - No

Back at the beginning of February, my oil pressure gauge started dropping to L at stoplights. This would only happen after the engine had warmed to normal temp. Because I wasn't low on oil at the time, I took it to my mechanic, who recommended having the sending unit replaced because oil pressure under the gauge was reading normal. So the sending unit was replaced, but the problem persisted.

In March, we loaded the vehicle down with people and stuff, and headed for Mexico on a mission trip, with no problems other than the usual needle dip at stoplights. While we were down in Mexico, COVID restrictions started happening and, since returning to the USA, we haven't taken any long trips.

Next development: Shortly after our Mexico trip, the problem started happening earlier during my drive, which could possibly be partly due to the warming weather. I also began to see the needle dip while coasting/braking to a stop, and I could watch the needle "bounce" with each downshift. That is, as the revs would increase slightly with each downshift, the pressure needle would bounce up a little during its overall downward trajectory. I took it back into the shop, and the mechanic this time measured 10 pounds of pressure at idle, 40 pounds at 2k rpm. He told me that, since that pressure was sufficient to keep the engine lubricated, he recommended not replacing anything at this time.

My two main suspicions have been (1) a failing oil pump or (2) a clogged pickup screen.

Around the same time, I also started to hear a wheezing sort of whine when the car is stopped. I don't know if it happens while driving under load, because the frequency is such that I wouldn't notice it while driving. The service tech claimed to know that sound as coming from the high pressure fuel injection pump, and that it's common in Nissans. I'm not entirely sure he wasn't full of it, and I'm starting to think the two symptoms are in fact related. Let me explain why...

Next development: Since my last visit to the mechanic, the needle drops below the L line more frequently, and the oil pressure warning light comes on when it does so. If I'll be sitting at a red light for a while when that happens, I usually just put it in neutral and give it a little gasórepeat as needed till the light turns green. Just in the last couple of weeks, I've realized what I think is an important clue: I've never BOTH seen the oil pressure light AND heard the wheezing/whining noise at the same time. In fact, I can sometimes come to a stop, roll down the window, hear the noise, then hear it stop at approximately the same time or even the exact same time the oil pressure light comes on.

In about a month's time, I'm planning to take my three sons on a camping trip out of state in the mountains, and I'd really prefer not to have any catastrophic engine problems during the trip. Any help diagnosing the problem? Trying to decide what repair to sink some money into, if any.
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Old 10-07-2020, 12:14 PM
kphoger kphoger is offline
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2006 Pathfinder
 
Join Date: Aug 2020
Location: Wichita, KS
Posts: 3
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Update:

Took it to the mechanic about four weeks ago, told them to drop the oil pan and look for any obvious blockages, then go ahead and replace the oil pump if not. They dropped the oil pan and found pieces of timing chain tensioner guide. That's what the whine was. I have no idea why it would stop at the same time the oil pressure light would come on, but whatever.

So they replaced two of the timing chains, the tensioner guides, plus some gaskets. Of course, because there was no sign of oil leakage through the common (to us) spot on the rear timing cover, they didn't replace THAT gasket: they had no reason to suspect it. They did, however, replace the oil pump as requested. I figured that, at the very least, I would know my low oil pressure wasn't the symptom of a failing pump and therefore any persistent pressure issue would be less critical. Plus, most of the labor charges for replacing it were included in replacing the timing.

After getting a late and slow start on things (I don't think they were particularly looking forward to the job), they ran into several problems along the way. They encountered a hose clamp that was nearly impossible to access, and they had to drill out a bolt to remove the front timing cover. Then, when they were putting things back together, they broke a starter bolt; when they subsequently tried to drill it out, it went cock-eyed, and they had to spend half a day basically dremelling it out with diamond-tipped bits. On the home stretch, they ran into some sort of brake issue (not sure exactly what). I picked it up at around midnight on Saturday, with our camping trip planned for Monday morning. The problem of low oil pressure at idle remained, but at least now I knew it wasn't the pump and I could live with it.

I noticed a slight rough idle upon leaving the shop, but not a major one. The next morning on the way to church, it started clattering under the hood. After church, I had AutoZone run an OBD-II code scan and found codes for misfire and camshaft timing on one bank. So we borrowed someone else's vehicle for the camping trip, and I dropped our PF back off at the shop first thing Monday morning before leaving. On Friday, I picked it up. They said the CEL codes were due to a faulty solenoid and connector, which they replaced. And the clatter was the fan blades hitting the shroud (I had super-glued the shroud back together several years ago after a clip broke, and they'd had to re-fix their re-fix of that fix). The shop owner had driven the PF home one evening, driven it back the next, and it ran smoothly, with no new CEL codes. The mechanic test-drove it for 40 minutes before I picked it up, and it ran smoothly.

Two blocks after I picked it up, the clatter returned. Immediately back to the mechanic, who said they were just going to cut the whole darned bottom off the fan shroud. Upon pulling it into the bay, though, he told me the clatter was valvetrain clatter, not fan noise, and he was going to have to open up the timing again to see if one got off a notch.

I popped in yesterday, and their working theory now is that, when they were taking everything apart the first time, he set the variable valve timing phaser/sprocket on a magnetic tray, and that messed up the insides, causing things to not move as designed, in turn causing timing issues. The other bank's phaser/sprocket was not set down on that tray, and that bank wasn't throwing a timing CEL code. That replacement part is now on order and due in Friday.

Will update later as the saga continues.
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