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I know this has been asked probably a 1000 times

Old 09-16-2010, 02:47 PM
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Today I was driving my XJ and stopped at a light and looked down and seen as I was sitting the the oil pressure was at 0 but when I take off its goes to maybe 20-25. My question is what could be causing this issue. You guys know more than I do at this point. I just changed the oil last weekend so I know thats good. It does sound like it has a rod slightly knocking. You can hear it when it starts and in higher rpm's or is this just a lifter problem. Any advice from the pros would help.
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Old 09-16-2010, 02:51 PM
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Are you sure you put enough oil in it?

I would check the oil and see if some leaked out. I would be worried if mine was at 0.
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Old 09-16-2010, 03:07 PM
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Mine used to do that its the knocking I turned my idle up a bit and it drops to ten now I'm just waiting for my motor to blow. You don't need much pressure at low rpm. (im no pro) I changed oil pump and sending unit sending unit used heavier wieght, I can't get it to stay any higher
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Old 09-16-2010, 03:08 PM
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yeah I'm sure i did. That was my job for 5 years lol. But I'll recheck it. I'm thinking bad oil pump and if thats it i might as well put in some new rods and mains. Thanks for info tho.
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Old 09-16-2010, 03:11 PM
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Originally Posted by mychero89 View Post
Today I was driving my XJ and stopped at a light and looked down and seen as I was sitting the the oil pressure was at 0 but when I take off its goes to maybe 20-25. My question is what could be causing this issue. You guys know more than I do at this point. I just changed the oil last weekend so I know thats good. It does sound like it has a rod slightly knocking. You can hear it when it starts and in higher rpm's or is this just a lifter problem. Any advice from the pros would help.
Well, when mine did that the gauge was going bad. Got a new one from the dealership ... which ended up doing the same thing about a year later. That was about 4 years ago. I left it alone & my Jeep is fine.

But take that FWIW ... I'm no expert ...

Edit: I meant sending unit, not gauge. And it's just like G.O.D. said, they are known for going bad.

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Old 09-16-2010, 03:15 PM
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My 98 XJ us doing the same thing but when I am going down to road it is holding 40-45 pounds but at Idle it is dropout to 10 and under. Curious if it is a first sign of an oil pump having slack. Also my truck has a rough idle, have a tread up on tha issue lol. But I don't think my crappy idle/misfire would cause that type of oil pressure issue
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Old 09-16-2010, 03:22 PM
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My fiance's 98 TJ does this all the time. The sending units go all the time, and are known to be problem areas. If you want to solve the issue on a more perminent level, get an after market gauge from a reliable source, such as Autometer.

You'd know if your motor really had 0 oil pressure, it'd sound like an effing lawn mower. Very chattery and ugly sounding.

However, this isn't something to ignore unless you are sure its just a sending unit issue.
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Old 09-16-2010, 03:25 PM
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Yeah I have no loss of power or anything I'm thinking a manual pressure gauge would be my bet.
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Old 09-16-2010, 03:32 PM
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When my sending unit went my oil pressure gauge was clocked at 80 even if the engine wasnt running. but in all the jeeps ive seen and had the oil pressure is like 40-45 when driving. 35ish idling after warm and like 50 when cold.

-Mike
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Old 09-16-2010, 03:46 PM
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Yeah I just went to check the oil in it and it is fine. Also started it to check it again and seems fine now. I'm thinking sending unit, Manual gauge here I come. Thanks guys for the input and I'll have updates soon. And can any please tell where I could be getting a vibe from after about 55-60 down the highway. It is driving me nuts.
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Old 09-16-2010, 03:53 PM
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Originally Posted by mychero89 View Post
Yeah I just went to check the oil in it and it is fine. Also started it to check it again and seems fine now. I'm thinking sending unit, Manual gauge here I come. Thanks guys for the input and I'll have updates soon. And can any please tell where I could be getting a vibe from after about 55-60 down the highway. It is driving me nuts.
Front end issues will cause the vibration, if its not U-joints. Could be worn bushings, tie rod ends, etc.

Use caution when selecting gauges. I've heard horror stories about some gauges, I can't remember if they were mechanical or electronic. I just know one is a bad choice.
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Old 09-16-2010, 03:55 PM
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Tire balance is the main cause fir high speed viberations. Go to a shop and have them balanced, this is my job as a suspension tech to find those things. If you have a high speed vibe in your sear or floor board it is the rear tires that are either out of balance or a cupped. If you have a vibe in your steering wheel it is the front tires. Hope this info helps you out.
-Tex
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Old 09-16-2010, 04:02 PM
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Gee oh Dee just to give you a heads up, Tierods normally don't cause a vibration, and definatly not at high speeds unless you are talking about hitting a pot hole or a bump. Tierods being loose normally will just cause slack in the steering wheel. A good way to find out if it is U-joints is two ways going from park to drive and there is a loud clunk it is a high possiblity that they are bad or while driving down the road and when you let off the gas you get a rough viberation but when you get back on the gas it goes away that is a tell tell sign of U-joints.
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Old 09-16-2010, 04:40 PM
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As long as the pressure goes up when you hit the gas your pump is probably ok, but a new sending unit should solve your problem for now.
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Old 09-16-2010, 08:41 PM
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+14. Everybody else has it right. I got nothing to add.
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