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How would I know if my oil pump is going?

Lately when I drive my van a 1995 dodge ram 2500 when I have my foot on the gas oil pressure is fine. As soon as it idles I see the oil pressure start dropping almost a line on the gauge. I just topped up the oil the other day so now its full it wasn't to far from being full and still in the safe range. If my oil pump was going though would the pressure ever drop all the way and then go back up? And if it needs replaced how much would I be looking at. Could I just need a lighter weight of oil currently using 10W40 with almost 153000 miles on the engine. Thanks in advance.

Update:

I have a few suggestions my question would be what is a solution to correct the problem is it safe to drive it or get it to my mechanic and have him check it out. It will be going to have the radiator flushed soon so I would have them check it while they do the flush. But like I said what will correct the problem or is it nothing I don't want to ignore it and do damage but I don't want to worry about it and find out its nothing. Thanks again.

6 Answers

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  • 1 decade ago
    Favorite Answer

    It is normal for an older engine to have the oil pressure drop off at idle.

    The old rule of thumb is 10 psi for every 1000 rpm.

    If you have at least 10 psi at idle, the engine will be fine.

    At 3000 rpm you will need 30 psi.

    As long as this minimum pressure is met, you shouldn't have any problems.

    I have had some people sucessfully use Slick 50 or other teflon additive to increase the pressure a bit.

    Source(s): Auto tech 25 yrs
  • Anonymous
    1 decade ago

    ok , first off. im sure you know when oil gets hot it gets thinner. normal !that will cause a small drop in pressure. no big deal. keep your oil changed of course. you should be good as long as press. is in the safe zone.also dodges have oil sending units that leak sometimes , that could be a problem as well. you should see something like that leaving drips though. 10 40 should be good. i have a 318 , you probably havea 360. same motor basically . i run castrol 75000 plus miles i think 10 30. BUT if pressure drops and goes right back up it is more than likely that its the pressure sending unit.thats what was happening to mine .put a sender in it an its fine. gotta love them dodges. its like 15 or 20 dollars and its located in back on top by the disributor.

    Source(s): grant from last chance auto. 15yrs exp.
  • 1 decade ago

    If your pump was failing there would be no pressure at all. Older engines have less restriction to oil flow due to wear in the bearings and such. You could try using straight 30 weight in the summer and straight 20 weight in winter, that will increase the gage pressure.

  • 1 decade ago

    most likely its not the pump but the crank bearings that go to cause low oil pressures. lighter oil would do the opposite of what you think...pressure will drop because more oil is getting past the bearings.

  • Anonymous
    1 decade ago

    Your best bet is to take it to a reputable repair facility and have them check the oil pressure with a gauge, then compression check the engine.

  • your valve lifters will be making a tapping noise

    your car might throw a rod which cost a lot and is dangerous for your engine and it will make a pinging noise constantly and will get worse as you press the throttle but this is if you starve your engine for a long time

    it might just be your oil pump belt

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