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How do you know if an oil pressure gauge is bad or if it’s something more serious? ?

I have a 2004 Suburban and I’ve noticed the oil pressure gauge will get low when I’m stopped at a light and then will start making a beeping noise. When I start driving again it goes up and it stays up while I’m driving and every time I stop it starts to get low again. The car drives quiet and there’s no noise coming from the engine at all that’s why I’m thinking the gauge may be bad. I also just got an oil change about a month ago and i checked the oil and it has a lot of oil. Any ideas? 

11 Answers

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  • 2 months ago

    That can be a few reasons. A common one is old oil. Older oil is thinner than new oil. Also, check the oil level. And sometimes this is just how things are. Slower engine speeds reduce oil pressure.

  • 2 months ago

    Did they change the oil filter? If not you might be pumping oil thru a clogged filter. Add 16 years of engine wear and you get low oil pressure at idle.

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    • M.
      Lv 7
      2 months agoReport

      The oil filter has a bypass valve in it, and the engine itself has another bypass valve, so a totalky blocked filter wouldn't block all oil flow. 

      This situation is a puzzle. Is it blockage?  OR internal leakage? 

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  • 2 months ago

    Not likely this typical wear and tear issue happened over the past month. I'd do something simple like, 1st check the oil level. 2nd take note if the oil looks clean. 3rd if the oil looks full and clean, then dump a 15 ounce bottle of STP in the engine and then observe the oil pressure. Too often the oil change clip joints either don't change the oil or they just dump "whatever" in the crankcase so they may have dumped some 0W20 in the engine instead of 5W30 or whatever it is supposed to have in it.

  • CB
    Lv 7
    2 months ago

    Change to a higher weight oil and try again - it may delay the inevitable (170k miles is substantial) for quite awhile. 

    Likely it was filled with 5W-30 change to 10-40 or 20-50 and see if it still drops pressure at warmed up idle.

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  • 2 months ago

    You have a mechanic hook up a mechanical oil pressure gauge at the sending unit port and check the oil pressure there.

    It's usually a bad oil gauge sending unit unless you hear the lifters clattering.

    The sending unit fails because of people not changing their oil and filter every 3,000 miles or 5,000 miles when using synthetic oil.

    Sludge builds up in the sending unit.

    Source(s): Mitsubishi Master Tech
  • 2 months ago

    worn mains bearings ..not your gauge or sender ..as you say its consistent ..no deviations ..if you live in a warm state ..not frosty this time of year ..consider upgrading your oil ..you guys in america use very thin oil compared to us in europe ..few years back we all used 10-50 grade ..now its more like 10-30 or 40 ..fords latest all singing and dancing oil is 10-60!!.they say you can use it in hypercars ..so find out what grade you use and up it ..it will be thicker longer ..will increase pressure 

    • Dan
      Lv 5
      2 months agoReport

      You've never had an engine apart have you, rod bearings always fail before mains and the reason is obvious. You need to brush up.

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  • You engine &/or your oil pump are old & tired & both probably have excessive clearances that are causing your oil pressure to drop when the RPMs drop.  I bet it makes good pressure when you start it in the morning & it is cold. Next time you come to a light & the pressure drops, use your foot to increase the idle & you will see the oil pressure rise.  (The gear that turns the oil pump is usually driven off the distributor or the cam shaft.  Hence, the faster the engine turns, the faster the pump turns.)

    I'd be willing to bet a small amount of money that there is nothing wrong with your sensor or your gauge, but if you want to spend the money to change 'em, it's up to you.  You will see the same thing & now you will have an extra sensor & gauge.

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    • When I told you about the cars I had that didn't make much oil pressure but ran anyway, they were old as the hills & I didn't much care about them, & they gradually made less & less pressure; not all of a sudden like that.  But good luck.

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  • Anonymous
    2 months ago

    Replace the oil pressure sensor.  Check pressure with a mechanical gauge and see if you have a bad gauge.

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  • Dan
    Lv 5
    2 months ago

    Gauges rarely fail but GM oil pressure senders are very problematic. You can spend money diagnosing with a mechanical gauge or simply replace the sender unit, they aren't very expensive. If the problem persists after the new sender then you likely have a serious oil pressure problem.

    Mileage would be helpful?

  • Anonymous
    2 months ago

    Oil pressure is one of those things that will ruin an engine very quickly, I would get it looked at sooner than later.

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