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Old 05-05-2015, 10:34 PM
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'00 low oil pressure

So I just bought a 2000 sport with 145k and the oil pressure is running low, about 20... and drops completely at an idle. Drove it home, no problems (about an hour - super rural)... figured it might be the sensor? but the last stretch is a nasty hill about 8 miles at a 9% grade. She didnt like that and ran real hot... and when I took my foot off the gas, she gave a high pitch squeal. My thought: oh crap. what did i get myself into? My mechanic says he doesnt think its the oil pump, but maybe the radiator? he hasnt seen it, just his response after me explaining what happened. My 93 rocked and went 315k... and I was so excited to get another, but maybe newer isnt better? any thoughts?
should I be concerned about driving it into my mechanic (about 25 miles, with hills)?

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Old 05-06-2015, 12:08 PM
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Re: '00 low oil pressure

Welcome to the garage. No experience on the 4.0 myself, but i understood that the crank bearings can wear and lower the oil pressure.
If the pressure really becomes 0 at idle, you should get some mechanical noises. The hydraulic valve lash adjusters will start making ticking noises.
You could put a new oil sending unit on it first, then you know for sure if the pressure is low.
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Old 05-06-2015, 03:17 PM
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Re: '00 low oil pressure

Quote:
Originally Posted by Frango100 View Post
Welcome to the garage. No experience on the 4.0 myself, but i understood that the crank bearings can wear and lower the oil pressure.
If the pressure really becomes 0 at idle, you should get some mechanical noises. The hydraulic valve lash adjusters will start making ticking noises.
You could put a new oil sending unit on it first, then you know for sure if the pressure is low.
Agreed. The oil pressure sensors on the 4.0 were notoriously bad--but quite cheap and simple to replace. Or, your mech should have a precision one that can be used to check yours.

I'd expect a bit of cold clunking if the crank bearings were worn enough to drop pressure notably.

Just in case, you might want to drop a can or two of STP Oil treatment into the engine, as it can help avoid casual damage--some folks ran the Baja with an oil leak and just STP.
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Old 05-20-2015, 04:07 AM
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Re: '00 low oil pressure

If you got it hot going home, check for coolant in the oil or tailpipe. The 00/01 really don't like getting hot and can blow a head gasket or even crack the head which could also result in low oil pressure.
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Old 06-30-2015, 01:28 PM
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Re: '00 low oil pressure

Before you go putting any money into it, look for the 4 digit code between cylinders 3 and 4 on the head (driver's side), if it's 0331, it's almost guaranteed that you have a cracked head.

Regardless, have a pressure test done at a Jeep mechanic that knows XJs.

Replacing cam bearings or sensors or anything else is a waste of money, as the cracked head is the issue. Even if you get a replacement head, who knows how long the previous had been cracked and what damage it did down the line.

This issue put my Jeep to the graveyard with less miles than yours.

Not trying to be negative, but rather trying to save you any more money.
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