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Old November 20th, 2020, 13:41
Redsnake Redsnake is offline
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Low Oil Pressure, Bearings, etc... some questions

I wanted to start my own thread about this and get some input. I've posted a couple bits of info tagging along on the end of this thread: https://www.naxja.org/forum/showthre...#post246711918

So my '01 XJ, 4.0 Auto has the typical low hot oil pressure. Currently has 181K miles, replaced crack 0331 cylinder head @ ~ 110K miles. Been running fine every since... but I did not have any bearings replaced w/the head was. Noticed this past week that my Oil pressure gauge dropped to 0 / check gauges came on when idling at stop light this week on my way home from work.

Bought a mechanical gauge, pressure when hot reading a steady 15 psi at idle and jumped up to ~ 45-50 psi when revving to 2K rpms. After letting her idle for 10-15 min w/gauge hooked up the pressure dropped slightly to ~12 psi. I changed out the Pressure Sensor and it was reading about the same 12 psi on my dash. This morning I drove to get some coffee and while cold the Oil Pressure is ~ 55 psi... dropped down to ~ 25 psi on the gauge before I got home. Was up to full operating temps, but I had only driven it 3 or 4 miles... so not really too hot.

Also, just changed my oil ~ 1K miles back and have been running Rotella T6 5W-40 and BG Oil additive and Wix 51515 filter for the last 50K miles or so.

That all being said... I know my bearings could be shot or I'm on borrowed time, so I wanted to get some input on what bearings to replace and how do I know if they're Standard, over, under, etc w/out taking the engine apart first? Engine has never been rebuilt as far as I know. Any input or links to said work is appreciated. I can't seem to find the info I'm looking for my googlfoo these days.
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Old November 20th, 2020, 14:31
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1990JEEPXJ 1990JEEPXJ is offline
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Re: Low Oil Pressure, Bearings, etc... some questions

I run 15w-40 and Lucas in mine. I’d say you’re fine. It’s not making noise and is running fine. Sure it’s a little low but how often are you idling? And you have better pressure at higher RPM. I’d just up the viscosity and run it. Or if you’re motivated you can pop the pan off and pull a main cap to inspect the bearings to give you a concrete answer.
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Old November 20th, 2020, 14:37
tech1001 tech1001 is offline
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Re: Low Oil Pressure, Bearings, etc... some questions

You can change all the crank and rod bearings and it will help a little if you add a high volume oil pump will help some more , the only bearings you can't change with out removing the engine are the cam bearing but if you do the crank , rod with the pump the oil pressure should hold at about 20 maybe 30 psi when hot .
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Old November 20th, 2020, 14:46
Redsnake Redsnake is offline
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Re: Low Oil Pressure, Bearings, etc... some questions

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Originally Posted by 1990JEEPXJ View Post
I run 15w-40 and Lucas in mine. Iíd say youíre fine. Itís not making noise and is running fine. Sure itís a little low but how often are you idling? And you have better pressure at higher RPM. Iíd just up the viscosity and run it. Or if youíre motivated you can pop the pan off and pull a main cap to inspect the bearings to give you a concrete answer.
Thanks guys... and I don't know if I mentioned... but it runs just fine. No rod knock, lifter knock, rocker arm knock/tick that I can hear. Just the usual vibrations and rattles from HD Engine and Transmission mounts and the usual LCA/UCA's and such. Been thinking of running 15W-40 so I may do that... just do another oil change early to see how it works. Funny thing is, it's the end of November and here in OK the weather feels more like early Spring. Days in the 70's, mornings in the high 30-40 range. It's almost perfect weather... Ha.
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Old November 20th, 2020, 16:37
Unclewolverine Unclewolverine is online now
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Re: Low Oil Pressure, Bearings, etc... some questions

Well, you can take it from me. I had the exact same scenario in my crappy 01. Cracked head, watered up the oil, changed head, had almost exact same oil pressure reading except it kept declining over time, (i have a 140 mile per day mail route, so I probably put on a lot more miles than you,) I changed the rod and main bearings, (like you no noise but the bearings were absolutely horrible,) and put in a high volume oil pump. It did not help. From what I've gathered when you water up the oil it scrubs the cam bearings and thats where you lose all your pressure. Im pretty sure you have to pull the motor to change those. At that point I called it, (that was a the last straw in a long fight to keep that junker on the road,) scrapped it, bought a 95 and never looked back. Hope your fight goes better, but you may start looking for a long block just in case.
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Old November 21st, 2020, 17:06
halmca halmca is offline
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Re: Low Oil Pressure, Bearings, etc... some questions

Your oil pressure is normal. If you take the engine apart for other reasons, sure, replace the rod and main bearings, but it just ain't gonna make that much difference.
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Old November 25th, 2020, 17:40
SpringDog SpringDog is offline
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Re: Low Oil Pressure, Bearings, etc... some questions

I just made a post similar to this and waiting for a moderator to post it. I have a 2001 that is losing oil pressure when hot, also losing coolant over time. Oil is not milky but I did have milky oil on the oil cap on top of the motor. 215,000 miles, I've owned it since it was new, I love this thing, its in excellent shape. What would you do if you were in my spot? Replace the head? Get new motor? Buy another Cherokee for parts and the pull motor to put in mine?
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Old November 25th, 2020, 17:50
Redsnake Redsnake is offline
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Re: Low Oil Pressure, Bearings, etc... some questions

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Originally Posted by SpringDog View Post
I just made a post similar to this and waiting for a moderator to post it. I have a 2001 that is losing oil pressure when hot, also losing coolant over time. Oil is not milky but I did have milky oil on the oil cap on top of the motor. 215,000 miles, I've owned it since it was new, I love this thing, its in excellent shape. What would you do if you were in my spot? Replace the head? Get new motor? Buy another Cherokee for parts and the pull motor to put in mine?
So I changed the oil a couple days ago.. went w/Rotella T5 15W-40 and Wix 51515XP. Pressure was better at cold start up but it's still falling to the ~ 10-12 psi when hot and after continued stop-go traffic... and even having cool temps outside 60 degrees.

I'm pretty sure I'm going to need a rebuild or replacement for me. I called a local mechanic and he's going to get back w/me on a reman Jasper motor. I'm also going to call around to a couple other shops and try and get some quotes. I just don't want my rig blowing up on me while driving, in the freezing temps, or rain or late at night, etc... I'd rather be pro-active.

Also, is there a way to know if your bearings are shot other than taking the block apart and visually inspecting? Is there any other way to diagnose that?
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Old November 25th, 2020, 18:32
SpringDog SpringDog is offline
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Re: Low Oil Pressure, Bearings, etc... some questions

If you have oil pressure and its not completely dropping to zero I would continue to drive it and not drop a lot of money into it. Also, you could have an oil pump going out or the pick up tube could be plugged. But, as long as you have oil pressure then I would continue to drive it. Just my 2 cents.
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