Pathfinder Oil pressure

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Fofiddy
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Pathfinder Oil pressure

Postby Fofiddy » Mon Mar 03, 2008 2:19 am

Anyone ever notice how much their oil pressure fluctuates?
I've noticed the oil pressure will drop pretty low when the vehicle isn't in motion. Anyone else experience this, normal, reason for concern?


amr40509
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Postby amr40509 » Mon Mar 03, 2008 4:49 am

I have an '06 V6 w/ about 39K miles on it.


Since new the oil pressure has been consistant. On start up until the oil gets warm it will fluxuate with the rpm from about 5/8 of the way up the 'normal' scale to the top of it. So if I get on it before the oil thins down from heat, it will go up to the top of the scale.

After it gets warm w/in a couple of miles even on a really cold day (for Kentucky, so like 15F) it will be consistant. After it is warmed up, it does not move much at all, pretty much stays solidly at about 5/8-3/4

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blink32
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Postby blink32 » Mon Mar 03, 2008 5:03 pm

Mine doesn't fluctuate at all. Well, no further than 0 when off to roughly in the middle once started.

Being essentially a dummy gauge its hard to say what Nissan is calling Low and High but I know what it means on a small/big block engine when the oil psi is low at idle and closer to normal at higher rpms.

Amr, what weight are you running and is it syn or conventional? Has it always done that from the get go? Again, pulling from knowledge of sb/bb's oil pressure in the H range would be a cause for concern to me. Depending on where the pressure gauge is located in the oil circuit it could easily indicate a blockage or low flow situation until the oil is viscous enough to move through. But I know jack about the Nissan blocks.

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Postby Gray » Tue Mar 04, 2008 2:37 am

Since this posting I've been watching the oil pressure gauge closer. Yesterday morning without the block heater plugged in I started the PF at about 10 degrees F and the needle point went up to about the center of the 'oil drop' just below the oil can spout on the gauge and after about 3-4 minutes it dropped about 1/16th of an inch to just below the oil drop and stayed there all day through varying types of long distance driving up to about 80 mph and also sitting idling for about half an hour,...never moved at all except when I shut off the engine, but I also noticed that the pressure takes 2-3 seconds to register after the engine is started.

I'm running a Motul 0W30 ester synthetic which stays liquid down to about -75 F and I don't fill the engine to full. After the engine is shut off for about 15 minutes the oil line on the dipstick is at about halfway between add and full and doesn't move from there between oil changes which I do about every 3000 miles at this time of year because of a lot cold starts, occasional short distance driving and some idling.

Actually it's always sort of bothered me that this gauge doesn't vary with rpm changes. Maybe the 05's got a more pressure sensitive gauge.

.

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Postby amr40509 » Tue Mar 04, 2008 4:21 am

blink32 wrote:Mine doesn't fluctuate at all. Well, no further than 0 when off to roughly in the middle once started.

Being essentially a dummy gauge its hard to say what Nissan is calling Low and High but I know what it means on a small/big block engine when the oil psi is low at idle and closer to normal at higher rpms.

Amr, what weight are you running and is it syn or conventional? Has it always done that from the get go? Again, pulling from knowledge of sb/bb's oil pressure in the H range would be a cause for concern to me. Depending on where the pressure gauge is located in the oil circuit it could easily indicate a blockage or low flow situation until the oil is viscous enough to move through. But I know jack about the Nissan blocks.
Very strange, it only moves for me when it's a cold start. I run Mobil 1 5W30.

Anyone else out there have an experience to report?

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Postby LittleStevie » Tue Mar 04, 2008 5:25 pm

I see something similar to AMR on my '05. On startup, the oil pressure responds with RPM until the engine is warmed pretty good. After the engine is warm, oil pressure is pretty solid at about 1/2 scale, except at dead idle, when the pressure drops to about 1/3 scale.

It's done this since day 1, so I've never worried about it. Nissan may have some type of thermostatic device built into the oil pressure regulator (if there is one) to ensure that the engine gets plenty of oil flow when the oil is cool and thick.

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Postby boogyman » Wed Mar 05, 2008 6:13 am

I've seen the same thing on several vehicles. The pressure will be about half till warmed up, then will drop when idling. It's nothing to worry about, you still have enough pressure, unless it bottoms out, but then you will get an engine light and will be in a world of hurt. My old Porsche did the same thing and it lasted a long time till I sold it.

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Postby amr40509 » Wed Mar 05, 2008 1:13 pm

Mine never drops below where it is in the pictures, is it going lower for you guys?

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Postby LittleStevie » Wed Mar 05, 2008 6:34 pm

I'd say it's slightly lower at idle than in the pictures...I'll have to pay more attention tomorrow. The pictures show about what I see on a warm engine above idle.

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Postby Fofiddy » Wed Mar 05, 2008 11:16 pm

Ok so I've been doing a little reading about the low oil pressure readings. Since I have just a tick under 50k I can dismiss rod or cam bearings leaving:
Oil pump
Pressure relief valve (stuck open)
Oil pressure sensor

I'm using the Mobil1 5w-30 truck like may others, with a Mobil filter (just switched from Fram last change under a friends reccomendation).
All of you with rock solid idle readings with a warm engine; Are you using a Nissan or aftermarket oil filter?
I have a feeling there may be a built in pressure relife vavle in the OEM filter itself that may be lacking in the aftermarket filters... but haven't had the chance to swap filters to test that theory.

I'll post pics or a quick vid to show whats happenening asap, but basically once the engine is up to temp the needle sits at the safe side of the low threshold practically on the mark, once the engine hits 1k RPM the needle sits at dead center and does not budge up to redline.
I too will notice the needle move up when going into higher rpms when the engine is cold (due to the cold oil's thickness) but as a general rule I try not to exceed 3Krpm untill I'm fully up to temp.
Thankfully never recieved any warning lights so I'm in the clear. I've heard of this alot from Frontier owners...

Another tidbit: I was perusing through the service manuel and it was very clear that when changing oil, to always have the dipstick pushed all the way down. What gives? What harm could come from having it open for a little more flow when filling/draining your oil ?

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Postby Gray » Wed Mar 05, 2008 11:22 pm

Fofiddy wrote:All of you with rock solid idle readings with a warm engine; Are you using a Nissan or aftermarket oil filter?
Nissan stock.

.

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Postby blink32 » Thu Mar 06, 2008 4:12 am

I only use stock Nissan filters. 5w30 Mobil 1

Ok, I found the part in the Service Manual about not removing the dip stick. I was looking in the wrong manual.

I supposed more of a precautionary/cost savings deal than anything. If it's not removed the tech can't lose it or more importantly lay it somewhere that either the dipstick or vehicle and dipstick could get damaged. IE: lay it on the fan shroud then starting the vehicle and having it roll into the fan. They also wouldn't forget to replace the stick before starting the vehicle allowing oil to probably spew out. And less likely to completely forget to reinstall it when the job is done. I bet more mechanics than I would like to know about simply put in X amount of quarts of fluid and call it full without actually checking and therefore don't realize they've left out the dipstick.
Last edited by blink32 on Thu Mar 06, 2008 4:38 am, edited 3 times in total.

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Fofiddy
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Postby Fofiddy » Thu Mar 06, 2008 4:17 am

http://www.thenissanpath.com/filelib/R51/Service/LU.pdf

Page 9 between steps 6 and 7...says do not pull out oil level gauge
no make-o senso

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blink32
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Postby blink32 » Thu Mar 06, 2008 4:19 am

I was looking in the wrong manual. Ha. There are tons of disclaimers and notes like that in the Air Force TO's for working on Aircraft. Keep lazy mechanics on their toe's.......hopefully.

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Postby amr40509 » Thu Mar 06, 2008 4:36 am

Nissan filter, Mobil 1 5w30 Truck and SUV (unless they are out of it, then just regular 5w30...figure it's probably exactly the same).

Like I said before, but just to clarify.

Cold start at idle -- where the first picture is.

As RPMS/engine load increases it will come up until warm.

The warmer it gets, the less it moves, until it stays steady at all loads/RPMS at a point a little higher then the pictures.


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