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Thread: XJ Oil Pressure

  1. #1
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    XJ Oil Pressure

    Buddy of mine has an XJ, with of course the 4.0 6cyl automatic. Lately once it has been driven for about 30-45min. the pressure drops from 40 down to about 20. He said the engine sounds good, no knocking or tapping like it would be starved for oil. He took the sender out of his wrangler because it has about 20 hrs. on it and it is still having the same results. Nothing seems different other than the gauge drops. It still runs great and has no noises. What else could it be? Do you think the motor is going in it? My 92 Cherokee did the same thing. At highway speeds (60-70) my presssure would be nice and high, around 40 I think, but after coming to a stop, at idle it would drop way down into the 20s. I never had an overheating problem with mine or any other motor problems.
    CrazyAsianofPa

    94 YJ on 33s. Welded rear, gutless 4 banger 5 speed, but a helluva lot of fun.

  2. #2
    Smart phone, dumb Wrecker! Wrecker's Avatar
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    Mine goes to almost nothing. Runs fine and no noise.
    Gotta be a special place in heaven for those girls who believe in making a lot of guys happy instead of making one miserable

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  3. #3
    I have grease stains on the knees of my dockers Muzikman's Avatar
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    Are you sure it's not just a real gauge that is really showing you the oil pressure?

    I am not sure what type of pump the 4.0L uses, but if it's cam driven, the higher the RPM's the faster it pumps and the more pressure you would build up.

    If you put it in neutral and give it gas, does the pressure rise?
    Jason "Muzikman" Beam
    Pittsburgh (Penn Hills), PA

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  4. #4
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    ^^^^^^^^^^ x2

    my yj with a 2.5 fluctuates with rpm, & my 300c does it too

  5. #5
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    My 4.0 runs a steady 25-30psi. and never changes. It runs just fine.

  6. #6
    Less posting, more wheeling!
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    99'tj 5'' locked cocked and ready to rock...on 35's---sold
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  7. #7
    Less posting, more wheeling! joshs1ofakindxj's Avatar
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    The XJ oil pump is cam driven and has a long service life, so ideally, oil pressure and flow increases with RPM.

  8. #8
    Less posting, more wheeling!
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    the idle psi of a 4.0 is 13psi at 750 rpm and 75 at 3,000 rpm thats the spec from ALLDATA
    99'tj 5'' locked cocked and ready to rock...on 35's---sold
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  9. #9
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    Thanks everybody!!
    CrazyAsianofPa

    94 YJ on 33s. Welded rear, gutless 4 banger 5 speed, but a helluva lot of fun.

  10. #10
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    XJ gauges= junk at best most of the time.
    Karma...... you will get it sooner than you think...

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