oil pressure - JeepForum.com
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post #1 of 34 Old 07-03-2013, 07:11 PM Thread Starter
josh1011
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oil pressure

What is normal oil pressure for the 4.0 with 87 octane and 200k miles

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post #2 of 34 Old 07-03-2013, 09:44 PM
BIGBADWOLF
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Depends on how much wear in the engine. Pressure is not a function, it is an indication of engine condition.
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post #3 of 34 Old 07-03-2013, 09:45 PM
cruiser54
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Quote:
Originally Posted by josh1011 View Post
What is normal oil pressure for the 4.0 with 87 octane and 200k miles
What's yours?

And BTW, octane rating of gasoline is in no way relative to oil pressure.

If you own a Renix Jeep, you'll want to check this out.

An index to over 30 write-ups can be found in the link below

www.cruiser54.com

My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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post #4 of 34 Old 07-07-2013, 08:43 PM
rmockelman
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My 93 at a warm upped idle is at 35. Normal driving is around 50

1990 Cherokee Laredo 2Dr
Stock for now
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post #5 of 34 Old 07-07-2013, 11:03 PM
Hudson
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The oil pressure spec. for the 4.0 is this:

*Not less than 13 psi at HOT idle
*Between 37-75 psi OVER 1600 rpms

Live To Die. You're Not Going To Get Out Of This One Alive.

Build Thread - http://www.ausjeepoffroad.com/forum/showthread.php?t=121903
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post #6 of 34 Old 07-08-2013, 09:38 AM
brettgorringe
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I have a 2001 Cherokee and my oil pressure reads about 40 when cold and slowly down to zero when it'd warmed up. But it still runs perfectly fine cold or hot. I replaced the oil pressure sending unit and the oil pump and I don't know what els would cause that. If anyone could help me please? The pressure goes up to 10 or 20 when acceleration but when I am just cruising it drops to zero again
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post #7 of 34 Old 07-08-2013, 03:49 PM
playbass
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Originally Posted by brettgorringe View Post
I have a 2001 Cherokee and my oil pressure reads about 40 when cold and slowly down to zero when it'd warmed up. But it still runs perfectly fine cold or hot. I replaced the oil pressure sending unit and the oil pump and I don't know what els would cause that. If anyone could help me please? The pressure goes up to 10 or 20 when acceleration but when I am just cruising it drops to zero again
Your bearings may be shot and the clearances are too big causing low oil pressure in your engine. Have you ever had coolant mix with your oil? Coolant eats bearings really quickly.
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post #8 of 34 Old 07-08-2013, 03:53 PM
brettgorringe
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I just bought it about a week ago and I have not changed the oil yet. How do know if any has got into the bearings? And what bearing are you talking about
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post #9 of 34 Old 07-08-2013, 03:57 PM
brettgorringe
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and also it has a hard time accelorating after like 65 mph itll go faster if you floor it but it wont keep up the fast speed without keeping on the gas real hard and rapping out the engine.
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post #10 of 34 Old 07-08-2013, 04:08 PM
playbass
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Quote:
Originally Posted by brettgorringe View Post
I just bought it about a week ago and I have not changed the oil yet. How do know if any has got into the bearings? And what bearing are you talking about
Apologies, I did skip a few steps. If you just purchased it, I would change the oil and filter immediately. Make sure you put a decent filter on there, like Wix or Mopar.

If you still have low oil pressure, you need to check it with a mechanical gauge to verify what you are reading on the gauge is correct. Oil Pressure Sending units go bad often enough.

Next, if you still have low oil pressure, you need to take a look at the main bearings, you may have damage to them caused possibly by coolant mixing with your oil. The 00-01 models have a bad head that cracks more often than the other years allowing coolant to mix with oil.
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post #11 of 34 Old 07-08-2013, 05:08 PM
brettgorringe
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Thanks for your help but I still have a couple questions. the head is new so where are the mmain bearings loacated and are they cheap and easy to replace?
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post #12 of 34 Old 07-08-2013, 05:19 PM
playbass
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Originally Posted by brettgorringe View Post
Thanks for your help but I still have a couple questions. the head is new so where are the mmain bearings loacated and are they cheap and easy to replace?
Check the other things I listed first before the bearings. This site has a lot of information on what to do next if you rule out the oil filter and oil pressure sending unit.

I've never done a bearing job, so I can't speak about how easy/hard it is.
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post #13 of 34 Old 07-08-2013, 06:00 PM
brettgorringe
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I'm new to thus site sorry this is my first thread. How do I find more info on the bearings? I just replaced the sending unit and did a oil change. Still funny pressure. I'm wondering if maybe I should sell it to someone who knows what they are doing or could I do it cause I really like this jeep its way nice.
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post #14 of 34 Old 07-08-2013, 08:53 PM
BIGBADWOLF
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Quote:
Originally Posted by brettgorringe View Post
I have a 2001 Cherokee and my oil pressure reads about 40 when cold and slowly down to zero when it'd warmed up. But it still runs perfectly fine cold or hot. I replaced the oil pressure sending unit and the oil pump and I don't know what els would cause that. If anyone could help me please? The pressure goes up to 10 or 20 when acceleration but when I am just cruising it drops to zero again
If it is running fine I would not worry about it unless it starts knocking. There have been MANY 4.0s that have ran a long,long time with low oil pressure.
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post #15 of 34 Old 07-08-2013, 09:12 PM
playbass
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Quote:
Originally Posted by BIGBADWOLF View Post

If it is running fine I would not worry about it unless it starts knocking. There have been MANY 4.0s that have ran a long,long time with low oil pressure.
This is true, too. While technically your engine is out of spec if you have 0 psi there are a lot of 4.0s out there running with the same issue.
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