1. Low Oil Pressure

    Hello All

    This is my first post. I am somewhat confused /concerned about the oil pressure on my 02 TJ, 4.0. This is all a bit new to me and I thought I would come to the "experts" for some advice I know this has been discussed here before, but I wanted to get an opinion on my particular case. Here is the low down.

    2002 Wrangler, 4.0 with 140,000 miles. Jeep starts and runs great. No knocking, pinging, etc... hot or cold. At cold start up, the Oil Pressure gauge shoots right up and stays there, even through warm up. Once at warm idle, at approximately 550-600 RPM, the pressure gauge stays above 0, about halfway between 0 and the first dot (which I assume is the 20 psi indicator). Once engine is hot, if I turn off and then restart, the oil pressure gauge does not rise, stays at 0. If I step on the gas and rev the engine a bit, the gauge rises and then falls back down to 0. If I drive for a bit, the gauge immediately rises and then stays above 0 until I turn it off again. Here is what i have doe thus far to try to address the issue. Note. my dash tach does not work, I use an OBD II scanner to tell me my RPMs.

    I replaced the sensor /sending unit 3 times. 1 aftermarket, 2 Mopar. Still doing the same thing.

    Next, I used a mechanical gauge. At Idle (approx 600 RPM) when warm, the mechanical gauge reads approx 5 PSI. At 2000 RPM when Hot / warm, while in neutral, the mechanical gauge reads approx 18-19 PSI. Turn Jeep off and restart while hot. The mechanical gauge goes to just below 5 PSI, at approximately 600 RPM. The gauge I am using is Harbor Freight, so it's not the best gauge around.

    Next I changed the oil to Mobile 1, Full Synthetic 10W-40 and put on a K&N High Performance Oil Filter. Still same result with Mechanical Gauge

    When I changed the oil, there appears to be no water or moisture in oil (milky) and a check of the oil and old filter (as best I could) reveals no metal shavings.

    I am not burning / losing oil.

    Just looking for any thoughts insight as to if this looks like i have an oil pressure problem (or is this normal) and if I do, what should I be looking for / doing next.

    Thank you in advance

  2. #2
    Join Date
    Dec 2010

    Re: Low Oil Pressure

    Check the coolant for discoloring or signs of oil. Observe coolant while at idle for any signs of bubbling. How does the exhaust look?
    White or balck or clear? Oil/discoloring/bubbles could be a sign of a blown gasget allowing oil and pressure to escape via the cooling or exhaust system.

  3. #3
    Join Date
    Feb 2009
    Dayton Ohio Area

    Low Oil Pressure

    You may have a oil pump issue. Blockage in the pickup? Worn bearings?? How many miles on the engine?

    Second you should be idling around 760 RPMs

    How do your plugs look ? Oily and sooty? If so do a compression check. Could be blow by from a ring, valve or valve seat.

    Never look down on anyone unless you are helping them up - Jesse Jackson
    Last edited by JPNinPA; 08-16-2021 at 02:33 PM.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

  4. #4

    Re: Low Oil Pressure

    i was going to say i think you have an oil pump problem, too.
    99 xj with 350k miles on it. Still runs great

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