Low Oil Pressure Vs Oil Pressure Sending Unit?

Discussion in 'SN95 4.6L Mustang Tech' started by Dchilders85, Oct 6, 2013.

  1. Hey all,

    I know there has been a lot of discussion about this in the past, but I'm trying to get an answer for my specific indications.

    Last week my oil pressure dropped started intermittently dropping to 0 then back up to normal during highway cruising. This happened maybe once every 60 minutes. A day or two later, it starts happens much more frequently, but only when stopped in traffic and under 1500 rpms. Engine temperature remained normal, no low oil light, and engine continues to run smoothly. Based on those indications and a quick read through the internet, I assumed it was the oil pressure sending unit going bad.

    Fast forward a week later. Yesterday the oil pressure drops to and stays at 0. No low oil light, engine temperature remains normal, no abnormal sounds/feel. I checked the oil level this morning, and it looked low if the oil was dirty/darker, but looked like it could have been normal with cleaner/lighter colored oil. I have not seen any signs of oil leaks underneath the car.

    I put two quarts into it for :poo:s and giggles and start it back up. Oil pressure gauge seems to be reading normal again.

    So here's my question. Have I been driving for the last week to little or no oil in my car? Shouldn't that have brought on the low oil light? I understand the concept of the oil pressure sending unit grounding at 6 psi, so is it possible I had enough oil to service the engine, but under 6 psi? How much damage did I just do to my engine?

    Thanks for the help!
  2. My Expedition did the same thing for a while until the engine locked up. Two things I'd be worried about is a bad oil sending unit or a clogged oil screen. Either way I don't think it will get better. What year is your car?
  3. +1 on above.

    The Stock oil pressure sensor is a simple on/off switch that's set to 6 PSI. Yes that is correct. 6 PSI. Sooooooo if the dash gauge goes to zero, that means the oil pressure is below 6 PSI!

    Oil pressure sensors can and do go bad. The part is cheap and easy enough to change out for trouble shooting reasons. If this were my car, I would do this without delay.

    The Windsor motor in my 2000 GT failed at 145K miles. Upon tear down I found that the plastic covering on the timing chains had wore down to the metal. The plastic debris fell into the oil pan and clogged the pick up tube. Thus starving the motor for oil. This affected mostly the top end of the motor at the cam towers.

    Note, the failure happened to the prior owner of the car. I bought the car with a blown motor and did the motor replacement as my project.

    To me it was a learning experience. I now have an oil filter cutter. With each filter change, I cut the oil filter open and examine for metal or any other debris. You see the motor could have been saved if the problem was detected and corrected earlier.

    Replacing a set of timing chain adjusters would have been cheaper than replacing an entire motor!

    There's a thread over in allfordmustangs.com 4.6 tech section titled "No oil pressure" posted by OhBandit. This thread may be a match for your issue. This is close to what the oil pick up in my motor looked like.

    #3 wmburns, Oct 7, 2013
    Last edited: Oct 7, 2013
  4. Put a manual gauge on it. That's what I did. I like knowing my exact pressure
  5. Not sure if putting oil in the front seat is a good idea.:shrug: