5.2 V8 oil pressure drops @ idle? - JeepForum.com
 
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post #1 of 8 Old 01-29-2015, 11:48 PM Thread Starter
JBZJ1996
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5.2 V8 oil pressure drops @ idle?

Hey guys, I'm new to the forums and I hope that some of you can help me. I've got a 96 ZJ with the 5.2 V8, and the oil pressure drops at idle and very low revs. But as soon as I accelerate, the pressure goes back up, albeit to a lower level than usual. My first thought was that it may be burning oil. Any other ideas? Just wondering if this is a serious issue, or if it's fairly common and easy/cheap to fix. Thanks!


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post #2 of 8 Old 01-30-2015, 12:30 AM
kensnelling
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You may just have a bad sending unit. You could test that by temporarily hooking up a mechanical gauge and see if the same thing happens then.

The only way burning oil affects oil pressure is if you burn so much out that your oil level gets too low.

Ken
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post #3 of 8 Old 01-30-2015, 01:52 AM
dflewelling
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I always use 10w30, never had a problem with it. That was on my old motor...it ran 20 at idle if I was lucky. Mine would do the exact same thing yours did, and it was especially evident when using 5w30. But I have a new motor now lol
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post #4 of 8 Old 01-30-2015, 11:24 AM
Uniblurb
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It would probably help if you posted your low and high end oil pressure readings. While my 96 4.0 is a different animal my oil pressure reads 20psi at idle while it never seems to go over 40psi.

Could kick myself for not replacing my oil pump while replacing the rear main seal/pan gasket but I'm not sure if it would have made that much difference anyhow. Especially since I've changed my oil every 3,000 miles since I bought it new. Could be worn crank bearings with 206K miles but as long as the valve rocker arms aren't rattling, and I can see oil flowing up to them at idle, I'm not going to worry about it. You may want to check the same.

A mechanical gauge to check your pressure, is a good idea as mentioned, and many auto parts stores have loaner ones. I've also heard where some oil filters can change the oil pressure according to the amount of flow through them. Good luck.

96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 96 4.0 XJ (son's)


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post #5 of 8 Old 01-30-2015, 11:32 AM
Boone96ZJ
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I have a 96 5.2 as well. I run 10w30 Rotella T5. I am at 39psi at idle and around 55psi at cruise but my crate motor only has 13K miles. Mechanical gauge verified and the dash gauge is right on too. It is very normal for idle pressure to be lower than cruise or acceleration. Old rule of thumb is 10psi for every 1000 rpm. So in theory, 10 psi is ok for idle but I wouldn't like that very much.

96 5.2 242 3" 32x11.5
https://www.jeepforum.com/forum/f13/1996-grand-cherokee-laredo-5-2-a-2570290/
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post #6 of 8 Old 01-30-2015, 11:55 AM
Cbob4
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Quote:
Originally Posted by Boone96ZJ View Post
I have a 96 5.2 as well. I run 10w30 Rotella T5. I am at 39psi at idle and around 55psi at cruise...
My '95 5.2, about the same per the dash gauge. 155K on the clock...
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post #7 of 8 Old 01-30-2015, 01:56 PM
94cherry
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My 5.2 with 210,000 miles on it runs 40 at idle and 60 to 70 at 2200 rpms.

Kiss my shiny metal bumper.
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post #8 of 8 Old 01-30-2015, 02:48 PM
Uniblurb
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Some screwy specs in the 96 FSM on oil pressure. I would have thought the 5.2 specs would be higher than the 4.0 on both the low/high end side. Specs for the 4.0 at idle (600rpm) is minimum 13psi while at 1600 rpm its supposed to be 37-75psi. The 5.2 minimum pressure spec is 6psi at idle while at 3,000 rpm's spec is 30-80 psi. They have a warning where if you have zero oil pressure don't rev the engine up to 3K rpm! No duh, lol!

96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 96 4.0 XJ (son's)


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