YJ 2.5L "correct" oil pressure (Jeep Newbie) - JeepForum.com
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post #1 of 18 Old 01-28-2020, 12:02 PM Thread Starter
broo1874
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YJ 2.5L "correct" oil pressure (Jeep Newbie)

Not new to off-roading. Have a Ranger and two Geo Trackers. But new to Jeeps. Just got my 95 YJ earlier this month and have a lot of work planned before spring. Hoping those of you with experience can share some insight as I start tackling getting it up to grade before spring.


My next thing to tackle is oil pressure. I already looked up the factory specs. But wanted to hear from those of you who run them regularly what they really see. 55mph in fifth gear what do you really run for oil pressure? I know my gauge is reading low and would like to know what is "normal" for a vehicle of this age with the original equipment never have been replaced so I know when I have fixed everything correctly. Just curious what you typically see while running yours at highway speed. I will likely put a new sending unit in first. But want some real world number to compare against once I change that out.


Also happy to hear you pipe in about anything "helpful" you might feel strongly about regarding this particular vehicle (aka I don't care about round vs square headlights. That isn't helpful. lol). Your insights might save me a headache in the coming months.

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post #2 of 18 Old 01-28-2020, 12:08 PM
bruinjeeper
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My pressure never drops below half marker on the gauge. And that's even on long road trips in the dead of summer.

In those conditions it will fluctuate between half marker and a hair before 3/4 marker depending on the RPMs. But never over or under those poles.

I also have the 2.5L. Upon start up... it sits a couple notches under 3/4 marker.

The OEM gauge system is also not the best.... or so I've been told. Mine is fairly accurate and has been since my rebuild.

Do you have a mechanical gauge?

EDIT: "correctness" of oil pressure is subjective to the condition of its components and engine. Etc etc.

Stop whining about the 'ride' - If your YJ ain't wrangling your soul free, then might I suggest you buy a stationwagon... at least you can fit all your bull**** in the back.
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post #3 of 18 Old 01-28-2020, 02:45 PM
GTS225
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Broo; The first piece of info you should supply is the mileage on the engine. If it's a paltry 75K, then there isn't as much bearing wear as if it's got 190K on the odometer, and bearing wear, (or clearances), will determine a lot about oil pressures.

Roger
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post #4 of 18 Old 01-28-2020, 06:14 PM
mike134
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I'm 14 psi at idle when hot outside and pinned to max on the highway. Been this way for at least 10 years.

when I had a job that was not time critical, O daily drove the YJ and I would have swapped in a new 4.0 if my engine blew.

now that I have an occasionally time critical job, I have a JL to daily drive.

few issues on the Yj for many many many miles though.
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post #5 of 18 Old 01-28-2020, 06:54 PM
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Quote:
Originally Posted by bruinjeeper View Post
My pressure never drops below half marker on the gauge. And that's even on long road trips in the dead of summer.

In those conditions it will fluctuate between half marker and a hair before 3/4 marker depending on the RPMs. But never over or under those poles.

I also have the 2.5L. Upon start up... it sits a couple notches under 3/4 marker.

The OEM gauge system is also not the best.... or so I've been told. Mine is fairly accurate and has been since my rebuild.

Do you have a mechanical gauge?

EDIT: "correctness" of oil pressure is subjective to the condition of its components and engine. Etc etc.
Yours is probably not accurate. It should drop way lower at idle when warm.

If you cannot fix it with a hammer then it has to be an electrical problem.
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post #6 of 18 Old 01-28-2020, 06:58 PM
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hmm.

I can't recall it ever doing so.

Great! Thanks Boojo, something MORE to think about *grumblegrumble*
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Stop whining about the 'ride' - If your YJ ain't wrangling your soul free, then might I suggest you buy a stationwagon... at least you can fit all your bull**** in the back.
~YJOTM MAY '16~
~YJOTM JULY '19~
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post #7 of 18 Old 01-29-2020, 11:28 AM
mark23
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My 95 2.5L with 150K miles, idles at just above 40 and climbs to about 70 at 55mph. Been reading the same way for the past 12 years.


My brother also has a 95 with 2.5L with 180K miles, but his does read slightly lower at idle, maybe 35 and it maxes out at about the same around 70.

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OME 2.5 (36R's front and rear) with MORE 5/8 shackles and 33x10.50 KM2's

1988 YJ 4.2L Mud Beast
3/4ton axles, 36" TSL's.

Previous Jeeps; 00 XJ 3.5 RE lift, 05 TJ Rubicon 2 RE BB lift
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post #8 of 18 Old 01-29-2020, 05:15 PM
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I just verified in the manual that 0 PSI = 1 ohm and 80 PSI = 89 ohms. So in a nutshell, as all of your cluster contacts and other connections get cruddy which these old Jeeps have issues with, your oil pressure will read higher.

The same is true for the fuel gauge. It was really poor engineering and it allowed gauges and circuits that were compromised by age, corrosion, etc to still read normal. 0 to 90 ohms was normal for most gauges, for many vehicles and manufacturers back in the day. It was kind of an industry standard. If you had cruddy connectors and no oil pressure, or out of gas, you would never know it. Many modern vehicles have reversed the way the resistance works the gauge. High resistance or ohms will default the gauge to a lower reading. It is a better be safe than sorry approach. The thing that sucks about the newer ones is there is no standard to what ohm or resistance ranges are high and low. The resistances are all over the place now. Even within a manufacturers own car line at times.

If you cannot fix it with a hammer then it has to be an electrical problem.
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post #9 of 18 Old 01-29-2020, 06:15 PM
mike134
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"poor engineering" we're having minor gauge issues after 30 years from a vehicle from a time when 5-8 year lifespan was normal.

They could have done better, but we could also switch over to more accurate mechanical gauges at this point. I'd say its about equal to the hassle of chasing down the electrical gauge gremlins. maybe a bit more investment than the OP wanted though.
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post #10 of 18 Old 01-29-2020, 06:45 PM
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Originally Posted by mike134 View Post
"poor engineering" we're having minor gauge issues after 30 years from a vehicle from a time when 5-8 year lifespan was normal.

They could have done better, but we could also switch over to more accurate mechanical gauges at this point. I'd say its about equal to the hassle of chasing down the electrical gauge gremlins. maybe a bit more investment than the OP wanted though.
No. It really was poor engineering. I do not care what the life expectancy of the vehicle is or was. If the simple push on oil pressure gauge connection with no locking tang, weather pack connection, etc. came unplugged or had a poor connection through its poor design problem, it told you all was good. It was a bad default. It cost manufacturers money in the warranty period. Stuff fails before the 30 year time limit. Stuff failed within the warranty period which is why it was all re engineered.

You need to understand why defaults in a vehicle are designed the way they are in the modern day. Why would you ever want to make a worn out circuit seem ok????

If you cannot fix it with a hammer then it has to be an electrical problem.
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post #11 of 18 Old 01-29-2020, 09:16 PM
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The F7 key on my commodore 64 no longer works... how dare they build this piece of trash....

do you expect the rubber parts to last beyond the life of rubber? why do you expect metal to last beyond a reasonable corrosion period? dielectric capacitors to last beyond the dielectric lifetime?
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post #12 of 18 Old 01-29-2020, 10:55 PM
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Back when I had the 2.5 in my Wrangler its would idle at about 20psi hot and 60 psi at speed. It had a 130k miles on it and ran fine till I swapped in the 5.7 Vortec. What numbers is it showing?
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post #13 of 18 Old 01-30-2020, 07:10 AM
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and ran fine till I swapped in the 5.7 Vortec.
Hey, Mrit! Does that suggest that it no longer runs fine?

Roger
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post #14 of 18 Old 01-30-2020, 06:00 PM
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Originally Posted by mike134 View Post
The F7 key on my commodore 64 no longer works... how dare they build this piece of trash....

do you expect the rubber parts to last beyond the life of rubber? why do you expect metal to last beyond a reasonable corrosion period? dielectric capacitors to last beyond the dielectric lifetime?
I don't expect things to last beyond a reasonable amount of time.

I am a mechanic for a living. I understand defaults that are built into cars very well. Some are very well thought out. Many trans codes for instance default to maximum line pressure. Why? There is less chance of slippage and damage while the code is present.

The default in the old days on gauges made them read high with corrosion and excess resistance. I live in a salt belt state. Corrosion is a fact of life and stuff does not last forever. I get that. What I am saying and the way stuff now is. High resistance in a gauge now in many instances would read 0 rather than give you a reading that is good. Would you rather have an oil pressure gauge that reads low and the engine has oil pressure or have no actual oil pressure and have the gauge read ok? Me thinks that the latter would be the more likely one to lead to catastrophic failure. JS.
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If you cannot fix it with a hammer then it has to be an electrical problem.
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post #15 of 18 Old 01-31-2020, 12:54 PM
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I had 2 2.5's and 2 4.0's all with over 200,000 miles. All idled at 20psi ran 40psi up to 2000rpm's amd over 2,000rpms read 50psi. Cold they all ran 70psi till the oil got warm. The gauges were all within 5psi of what my mechanical gauge read.

1995 YJ. 2 inch BDS Spring lift. 1 inch shackle lift. 1.25 inch JKS Body Lift 33x12.5x15's. Engo 10,000 pound winch.

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I gave the Jeep the required offering of $$, sweat, and blood, and everything works fine now. -- Jim
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. It started with a $200 axle, and a few thousand dollars later I was done :)
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diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

Ask me how I know...
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this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.
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