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Discussion Starter · #1 ·
Hi guys,

I've got some problems...... I need help/advice.

My TJ has been running really low oil pressure for the last couple of months. It all started after I sank er a while back. Although I didn't hydrolock it, I ended up taking in some bog water through the leaking rear main seal.

Since then I have:

Replaced the Rear Main Seal,
Replaced the Oil Pressure Sending Unit,
Ran STP Engine flush through her twice,
Changed the Oil 3 times (over the last 6k miles) currently using 5w30,
Put that fangled Duralube in first and later that shit they use in airplanes that was on the infomercials for your car (name escapes me),
Checked the Main and Rod Bearings for end play etc (all OK),

All of this to no avail.....

Currently, after a cold start the Oil Pressure sits at the 1/2 mark (Forgive me for my laymans terminology as my gauges are in BAR (Metric) rather than PSI), as it warms up it sits at the 1/4 mark. Regardless of wether im driving in town or doing 75 mph it never goes over the 1/4 to 1/3 mark.

Before this all happened, my Pressure used to be at the 3/4 mark when cold, and usually at the 1/2 mark during normal driving, and just over 1/2 during Hwy driving.

Also, I seem to have a bit more Valve Train Tick than before, and she also knocks a bit while i'm maintaining speed on the road (ie. sounds fine during acceleration and deceleration). I also get the "Check Gauges" light when I return to an idle at a Stoplight right after i've been on the Freeway; thing is when I stop the Gauge sits at the 1/8 mark and suddenly drops right off to nothing.

So WTF should I do with it??? Anyone have any suggestions??? i'm wondering if this thing can be salvaged, or should I start looking for a rebuilder???

The only thing I can think of that I havn't replaced is my Oil Pump.... Is this the most likely source of the problem???

Thanks

Scotty
 

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Mr. Personality
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Only things i can think of are... Bad oil press. sending unit, bad oil pump, oil pump relief valve stuck open, pump cover warped or cracked. First of all , i'd get a mechanical gauge and check your pressure with that.. minimum press on the 4.0 is 13 psi at 600 rpm. should be at 75 psi at 1600 rpm. More than likely though, your pump is bad, seeing as you took your engine for a swim and all that mucky shit leaked into your oil supply :rolleyes: .. if the mechanical gauge reads bad too, do a visual on your pump, and check gear clearance/condition. HTH
 

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Discussion Starter · #4 ·
Thanks for the great advice...

i'm gonna give the mech gauge test a whirl. All signs point to the pump :( Thats the price of having fun I guess.

BrandonK, would you part with that stocker you have?? Whats it out of etc.

Thanks

Scott

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I never trust a factory gauge. You can not trust a gauge that is not graduated, repeatable, and reliable.

Oil pressure is pretty generic.
15 psi minimum at idle
45 psi minimum at operating speed (2000 RPM for my engine).
75 psi maximum

This has held true to everything I have worked on between deisels larger then an Excursion, all the way down to my VW. Of course, Harley engines don't apply :rolleyes:
 

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When you get ready to put that new pump in get some plastiguage and check the clearance of the rod and main bearings..I bet they are a little loose..
 

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I lost oil pressure after a similar situation. I swapped out pump and all lower bearings. No good. After tearing down the whole engine, I found the cam bearings serverely wiped out.
Rebuilt the whole engine. This was a 1990 4.2L.
 

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armybuck041 said:
Thanks for the great advice...

i'm gonna give the mech gauge test a whirl. All signs point to the pump :( Thats the price of having fun I guess.

BrandonK, would you part with that stocker you have?? Whats it out of etc.

Thanks

Scott

[email protected]
I honestly would but I can't find it when I do I'll PM you
 

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armybuck041 said:
Thanks for the great advice...

i'm gonna give the mech gauge test a whirl. All signs point to the pump :( Thats the price of having fun I guess.

BrandonK, would you part with that stocker you have?? Whats it out of etc.

Thanks

Scott

[email protected]
Ok, tell me this... What engine? 4 or 6? Also, how many miles. Mine does the same thing. I put 20-50 oil in it and it does ALOT better. stays at "the middle" while rpms are above 1500, and dips to 0 and then rises to 1/4 at idle.
 

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Discussion Starter · #12 · (Edited)
LordRatner said:


Ok, tell me this... What engine? 4 or 6? Also, how many miles. Mine does the same thing. I put 20-50 oil in it and it does ALOT better. stays at "the middle" while rpms are above 1500, and dips to 0 and then rises to 1/4 at idle.
Sorry.... Good point :)

115k miles... roughly (180,000kms)

I think I may try running the heavy stuff in the spring.... I used to run 20/50 in my 76 CJ 258, and it seemed to like it.

Just outta curiousity LordR, what you got under the hood...

Thanks

Scotty

(EDIT) Doh, you have a 2.5L..... Hmm, wonder if 20/50 will have the same effect on my 4.0l
 

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For future reference, always try to run the thinnest oil you can, while still maintaining correct pressure readings.

I run 5w-30 in my BII all the time, no matter how hot it gets.
 

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Drop the pan and check the oil pump.There are specs availble for this.If the pump is good then i would suspect something else like bad bearings.While the pan is off you can easily check the rod bearing clearance with Plastigage.
 

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I'm just a newbie :flipoff2: but I don't see how running thicker oil will really help your engine besides just making the gauge go up a little. From physics we learn that pressure is a force applied over an area. It takes more force to move the same amount of thicker oil than thinner oil. But that doesn't change the fact that your engine is fawked! or your oil pump is just worn.
 

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Had the same problem

I agree with robert..i have a 2000 sahara. guage would go to zero after warmed up and at a dead stop. took it to the dealer because i was still under warranty. expected oil sending unit...got it back 12 days later...bearings f'd up..love my strt 6...kept goin
 

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mellocj said:
I'm just a newbie :flipoff2: but I don't see how running thicker oil will really help your engine besides just making the gauge go up a little. From physics we learn that pressure is a force applied over an area. It takes more force to move the same amount of thicker oil than thinner oil. But that doesn't change the fact that your engine is fawked! or your oil pump is just worn.
If the engine components are worn, the oil will slip through the cracks much easier. Least, thats what I was told.
 

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"bog" water doesn't "seep" thru a leaky rear main seal. if it was
ablt to seep into the motor, you can imagine how fast the oil would be pumped out of the same motor while running. maybe a
little water could seep in.....

sounds like your motor is: worn out. lack of proper oil changes.

you sucked water into it in a water pit. then, did you fire the
motor up and drive it? I guess yes. then you just pumped dirty/
watery oil (with silt) thru your motor.

kinda like an extrude-hone machine.

You'll be lucky if it's the sender. less lucky if it's the oil pump.
Bad luck if the bearings/crank/cam is toast. rebuild time.

--Sherpa
 

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Heck, if you are going to drop the oilpan, you might as well rebuild the motor.

Take it out, have it flushed and bored if needed and replace bearings, pistions, and cam with new ones.

No sense tearing it down time after time for lack of oil pressure, when you have over 100k on it.
 
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