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-   -   Low oil pressure at idle - 05 Pathfinder LE 4.0 60,000 miles (https://x.nissanhelp.com/forums/pathfinder/10491-low-oil-pressure-idle-05-pathfinder-le-4-0-60-000-miles.html)

tomlennon 02-17-2009 08:26 AM

Low oil pressure at idle - 05 Pathfinder LE 4.0 60,000 miles
 
Please help -- I need a sanity check and any advice would be appreciated!

On my 05 Pathy, it indicates low oil pressure when the engine is warm, and the engine is running at idle speed. The needle reads below L on the gauge and the warning light turns on.

When the engine (and oil) are cold, the needle reads midway between L and H. This has not changed. But as the car warms up, the idle oil pressure drops. Still, when the engine is revved, pressure rises -- so at around 2000RPM, oil pressure reads around 30%-50% on whatever scale the gauge is indicating.

While driving, even though the warning light turns off, the oil pressure is lower than it used to be, and probably should be.

The engine is running extremely smooth, no signs of rough idle, knock, valve noise, etc. Dealer service had car, replaced the sender. I donít think that this is an electrical issue since the gauge reads properly when oil is cold. Dealer tech wanted six auth hours of labor to debug wiring harness and dashboard lights/gauges. Since the gauge reads consistently, and it shows the oil pressure as OK when car and oil are cold, I would conclude that the gauge and lights are in working order.

Somehow I think this is related to oil, either viscosity breakdown or flow impedance. Nissan service says car OK to drive, I think heís nuts, but I have it in writing.

Anyone have any bright ideas? I want to attack this logically. Am I crazy for thinking this is a problem that needs to be fixed, or am I worrying too much? Any other details you guys could use let me know and Iíll check it out.

Facts:

* Idle speed at 625 RPM
* Oil level OK
* 5W-30 motor oil (non-synthetic), Nissan Filter
* Oil change did not improve/change oil pressure.
* Engine runs great
* Coolant level OK


Other issues with car:

Dealer pressure tested radiator and found coolant leak at rear climate control device. Not a severe leak, but drips on exhaust. Thought was blown head gasket b/c of smell. May have another coolant leak in front of vehicle near secondary reservoir, but I am not 100% sure.

I think strut/swaybar is going. Low speed rolling causes slight clunking felt thru floorboard.

tech22 02-17-2009 02:34 PM

Sounds like the relief or valve the oil pump. Do you know if they checked the oil pressure sending unit?

tomlennon 02-17-2009 02:58 PM

Thanks!

Sending unit was replaced last week, no change -- still shows low oil pressure.

I think the timing assy has to be removed to get to the pump ... way out of my comfort/ability zone. Can I diagnose the relief valve without ripping the engine apart? Could something like the intake valve/timing control solenoids cause this?

The fact that the engine runs so well makes this so frustrating

tech22 02-17-2009 03:02 PM

Go to the service manusl at this site and read the section on eng lubrication.There it will tell you how to go about this.You will however need so basic tools.

NissanTech 02-17-2009 06:17 PM

Before replacing any parts, I suggest connecting a oil pressure gauge to the engine just to make sure is a low pressure problem and nothing else.

The information on how to check the pressure is in the "Engine Lubrication System" section of the service manual. You can download the section free from here: Knowledgebase - 2005 Pathfinder - Nissanhelp.com

tomlennon 02-19-2009 04:04 AM

Quote:

Originally Posted by NissanTech (Post 36270)
Before replacing any parts, I suggest connecting a oil pressure gauge to the engine just to make sure is a low pressure problem and nothing else.

What do you mean by nothing else?

I borrowed an analog gauge from a friend.

I think I'm getting "lower-than-it-should-be" pressure:

Warm at idle: 8psi +/-2
2500 rpm: 40-50psi (Measurement has some error in it: Measured with me on pedal, wife reading gauge and then with wife on pedal, me reading gauge)

Any ideas? Car still runs like a dream. 14-15 mpg city driving.

tomlennon 02-21-2009 05:21 AM

I'm x-posting this at another forum, too.

In case anyone's interested to comment, I'm investigating the following before I go after the oil pump (which equates to open-heart surgery...and I'm no more than a glorified male nurse).

I'm ASSuming the pop-off/relief valve in the oil pump is working correctly, since I get good oil pressure 40-45psi when the engine is cold, and the pressure will not go beyond 50psi when rev'd.

That leads me to think that this is a flow or viscosity issue.

So if it's a viscosity issue, I'm going to try flushing the cooling system. It's a long shot, but it makes sense to me: Higher temperature in a fluid causes lower viscosity making it harder to pressurize. The '05 has a secondary oil-cooler, and I've said earlier I had a small, under-control, coolant leak in the rear climate control system. If air or gunk has deposited itself in the oil cooler, it would decrease its performance, resulting in lower oil viscosity, thinner oil, and lower oil pressure. I see no cross-contamination in either the oil or the coolant.

Since this has a radiator and an aux tank, do I (and how would I) burp the system?

I'm also going to trade-up to 10W-30 oil for the viscosity boost.

If it's a flow problem, I have to get into the oil pan and check the strainer. I'm not excited about this job, it's 20 deg, snowy, and I don't have a garage...but I'll pop the lower pan off and see if there's a lot of gunk on the strainer.

Any thoughts or bright ideas? Thanks for replying

streamcast 02-21-2009 06:23 PM

What was the pressure at idle? The spec for idle is more than 14 psi and at 2000 rpm is more than 48 psi. The pressure you stated is a cold engine what were the pressures for a warm engine. Sounds like a possible sending unit/switch issue. Even though you said it was replaced. Check the oil level and make sure it is up.

tomlennon 02-21-2009 06:33 PM

Quote:

Originally Posted by streamcast (Post 36552)
What was the pressure at idle? The spec for idle is more than 14 psi and at 2000 rpm is more than 48 psi. The pressure you stated is a cold engine what were the pressures for a warm engine. Sounds like a possible sending unit/switch issue. Even though you said it was replaced. Check the oil level and make sure it is up.

WARM Idle pressure is low, around 7-10 psi. COLD idle pressure is around 45-50psi.

I've replaced the oil now, twice. First with five-weight, and I just did it again with ten-weight in to see if there was a diff (there was none). So much for my viscosity theory.

Bottom line: As engine temp. rises, oil pressure drops.

:badmood:

tech22 02-22-2009 05:14 AM

Back to the good old service manual.

Cyberpete 03-20-2009 06:26 PM

I had a 300zx back in the day and the oil pressure gage was very inaccurate. I was also concerned and had it checked. Pressure was fine. Problem could be the gauge is inaccurate at low pressure. Can you find an aftermarket gauge, hook it up and see if it is the same? Keep your eyes on the road and off the gauge, it must be driving you crazy.
Peter.

Jules3 04-22-2009 04:57 AM

Quote:

Originally Posted by tomlennon (Post 36554)
WARM Idle pressure is low, around 7-10 psi. COLD idle pressure is around 45-50psi.

I've replaced the oil now, twice. First with five-weight, and I just did it again with ten-weight in to see if there was a diff (there was none). So much for my viscosity theory.

Bottom line: As engine temp. rises, oil pressure drops.

:badmood:

Have you found/rectified the problem? I've noticed this a couple of weeks ago on my '05 SE w/ 38,000 miles. At first I thought I got a batch of bad gas because the RPM's and oil pressure would bottom out, the truck would shudder, then the RPM's/oil pressure would stabilize. Haven't gotten any warning lights. Only happened when the engine was hot and in Neutral. I wasn't going to worry about it until I went through another tank of gas.

Seth 04-29-2009 01:57 PM

Same Issue
 
I have a 2005 Pathfinder (SE), ~44,000 miles.

When I idle at a stoplight/stop sign, the oil pressure dips to very low levels and the engine begins to run very rough (enough to cause significant vibrations). As soon as I tap the accelerator, oil pressure climbs to normal levels and all roughness vanishes until my next stop.

The frequency with which this is occuring in this particular vehicle is disturbing - has anyone else found a solution?

tonyp112 05-13-2009 11:18 AM

Having the same issue on an 05 with 100k miles on it, any one figure this out?

Seth 05-14-2009 08:07 AM

Not yet
 
I have been to the dealership several times for exactly this.

First, they suggested replacing the oil and filter (I had just done so, less than 200 miles earlier). So I did - grabbed 6 quarts of 10W-30 Full Synthetic (they recommended 10W for our area in Central Texas) and a K&N oil filter (the best). After the replacement, the problem was minimally better.

So I went back to the dealership who decided (without contacting me) that they would dump $60 worth of brand-new oil and filters in the trash and replace them with their standard oil and Nissan oil filter. Then they charged me $98 for it. Problem became minimally worse.

So I went back to the dealership again, $160 worth of oil changes later, and was told that there was no problem (even as we sat in the car and watched the gauge bottom out and the car start vibrating).

I am frustrated beyond belief and I get the feeling that the dealership is either too prideful to admit they were wrong, or they want me to wait until things get so bad a check engine light comes on (by then, there has been damage done).

Too many people have had this problem for it to be coincidence.


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