Oil Pressure Fluctuation

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RogueFinder
Posts: 9
Joined: Sun Oct 07, 2018 6:17 pm
Location: Florida Panhandle

Oil Pressure Fluctuation

Postby RogueFinder » Sun Oct 14, 2018 7:28 am

Please see below in my signature block about my vehicle specifics.

Recently, after a brief off-road stint, involving water hazards, I did had no oil pressure readings/ warning light. Shut it down, physically checked oil and underside for leaks or damage-none. Removed oil pressure sensor connector, dried and cleaned out, re-installed with gob of di-electric grease. Cranked truck over and oil pressure back to normal, light out. BUT...now, when engine is warmed up and at IDLE (park or neutral), the dash oil pressure gauge (factory orig) reads " low end of gauge." No warning lights. Does not go all the way to "Low" mark. When driving and above ~1200 RPM, gauge reads in the normal range (middle of the range). No lights.

No visible leaking oil (drips, puddles) under the truck. No leaks seen around oil pan. I am about 250 miles since most recent oil and filter change. Still running 5W-30 oil. I have not connected a oil pressure gauge to the system to get actual readings. Do I have a faulty sensor? hidden leak or something much more sinister?

Any help is appreciated, thnx.


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ShipFixer
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Joined: Sun May 24, 2009 9:52 am
Location: San Diego, CA

Postby ShipFixer » Sun Oct 14, 2018 9:19 pm

They're kind of a known flaw, so maybe. I think mine was fluctuating all over the place when it went bad. Like really low at idle, then up and down slowly while driving. New sensor is fairly steady in the middle of the gauge.

Easy to replace so might as well try it?

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smj999smj
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Joined: Sun Jan 22, 2012 11:13 pm
Location: Prospect, VA

Postby smj999smj » Mon Oct 15, 2018 8:46 pm

You should have a 4.0L-V6 (VQ40DE) if it's a 2005 R51. You should hook up a mechanical gauge to test the oil pressure. If the oil pressure is indeed low at idle, the most likely cause is the oil gallery gasket has blown out on the rear timing cover. This is a fairly common issue on VQ35DE and VQ40DE engines. I know they make updated gaskets for the 3.5L, but I'm not sure on the 4.0L. Last I heard, they usually replace the entire rear timing cover assembly. It's a very labor-intensive job and the parts aren't cheap. Most will want to replace the timing chain set while in there...and not a bad idea to replace the water pump and thermostat, as well, at the same time. I did post a thread with a link to an article on the problem a while back. If the oil pressure tests good, then I would be looking at a faulty oil pressure sender or circuit issue.


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