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High oil pressure.

5K views 13 replies 7 participants last post by  Y-Yes 
#1 ·
Hi all. I'm in need of some help. I've got a 95 with the 4.0 and manual trans. I had a low oil pressure problem so I determmed it was not sender or gauge and took off the oil pan and looked at the mains. They didn't look bad so I put it back together. But I figured why not put in a high volume oil pump while I'm down there. Now I have high oil pressure all the time and a very noisy motor. It is new oil and a wix filter. Anyone have some advice ? Thanks ▫lllllll▫
 
#2 ·
More info is needed. What are your oil pressure readings, hot and cold idling, and at 2000 rpms, hot and cold? Hot, as in after at least 30 minutes of driving. Via a mechanical oil pressure gauge. What grade oil are you using?
 
#3 ·
Well at cold start it will be at 60 and noisy. Driving it will go up to 80 and stay there while I'm driving. After it is hot it doesn't really go below 40. And I've taken off the oil filler cap and I don't get oil splash out it. I'm running 10w40 rotella oil in it all summer.
 
#4 ·
Have you tried 10W30? Those readings aren't bad, however warm oil on the highway should be about 45-60 psi. The noise could be your lifters sticking or hanging up. What were the readings with the stock pump? Did you have noise with the stock pump? What filter were you using before the Wix?

I would first try a 5W or 10W30 grade oil and a different filter. A Fram Ultra is a good filter.

Normal oil pressure for the 4.0L is:

No less than 13 psi at hot idle. Some people claim 10 psi at a hot idle is OK.
About 37-75 psi over 1600 rpms. 45-60 would be ideal.
 
#6 ·
Without actually hearing it it's hard to diagnose. It could be a lifter, or something else. The high pressure could be the 10W40 is just too "thick" for that engine. You tried two different filters have you tried 5W30, or 10W30? With winter right around the corner 5W30 might be a good idea.
 
#7 ·
My 91 kind of does the same thing. I get a lifter tap on #2 when it's cold and the oil pressure is high. I have played around with it for years, and best I can figure is when the oil is cold and heavy, it gets a bit of airation. This causes the lifter to be a bit spongy. I use 5w30 most of the time, and I let the jeep warm up in the mornings. When it gets to temp, my oil pressure drops a but, and it is as quiet as a 4.0 can be. I did try 0w10 weigh oil this summer to see how it ran, and it was great, maintained oil pressure fine, and alot less tap tap in the mornings. I would use it tear round if it were easier to find in the shelf.
 
#9 ·
Okay, high volume oil pumps are never a good thing unless you get a deeper than stock oil pan. They rob about 15 ponies, can suck up an entire stock oil pan dry and can cause other issues. They are for high reving motors with deep pans only. If the crank is above the oil level in the pan because of a high volume pump, you're not lubing the main and rod bearings well enough.
 
#12 ·
+2 That's why small engines that don't have oil pumps have "Oil slingers" on the rods instead of the crank being immersed.

I'm not a big fan of high volume oil pumps for street motors, they put more wear and tear on the distributor and other parts, and they don't solve the real problem.
 
#13 ·
I'm not saying the crank gets submerged. High volume oil pumps are not for stock engines though period. They are for high reving motors, loose bearing clearances for main and rod bearings (.0025 or more). High pressure is totally fine, but high volume is not.
 
#14 ·
ClusterPuck,

Please see this post of mine--the excellent advice I received in it will, I think, answer all of your questions:

Are High-volume Oil Pumps a Good or Bad Idea?
http://www.wranglerforum.com/f218/are-high-volume-oil-pumps-a-good-or-bad-idea-1342345.html


For example, I fear/suspect that member 9T4YJ may be onto the cause of your valve noise--here is an excerpt (below) of his answer to my post, linked above (I added the bolding/colors, for emphasis):


9T4YJ said:
The factory gauges are only good for indicating that something is happening. With a pressure gauge plumbed in, 10-15psi hot at idle is what I'd like to see.

The high volume pump is good if you build the engine for it. You would need a higher volume pan, and then open up oil passages to allow flow to get to the parts you're worried about. A high volume pump should be used when you need to get more oil to the bearing surfaces, usually to the valve train. In addition, you would need to do clean up on the head to make sure oil can flow back to the pan easier. Installing a HV pump and not doing any other work will result in pump drive gear issues.

You might find an aftermarket that is the high end of the OEM range, but you'd likely have to run the pump and see what you get.
In other words, I received very similar advice from another friend of mine (not the mechanic I had put in the high volume pump, and who I'm now going to pay to replace it with an OEM pump--due to family health issues, I STILL haven't driven my YJ yet....).

My point is: this other, mechanic friend of mine (somewhat) echoed what 9T4YJ, Nubby55 and others said, in my original post, i.e., the HV pump could EMPTY the oil sump, and push too much oil up into the extra space under the valve cover, leaving the pressurized bearing surfaces STARVED FOR OIL.

I'm thinking that's what might be causing your valve noise--though I remember you said you opened the oil fill cap on the valve cover, and it was NOT flooded with oil inside. But did you do that with the engine running? (I can't remember....)

Hope this helps. Good luck.


Y-Yes
 
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