Oil pressure dropping

Discussion in 'Engine & Drivetrain' started by Musicars, Apr 18, 2018.

  1. Musicars

    Musicars Member

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    I've read all the posts regarding oil pressure drops but before I go ripping things apart I thought I would verify some of my conclusions.

    A couple of weeks back I noticed my oil pressure had dropped from around 40 psi at idle when warm to 30 psi. The next day I had around 20 psi at idle and around 35 psi as I accelerated from a stop up to 40 mph. The day after that I was at barely 10 psi at idle and around 20 - 25 psi driving. That night the oil pressure warning came on as I was backing into the driveway. If I revved the engine I could get it up to 20 psi and the warning would go off.

    Then we get nailed with two feet of snow so the truck is sitting in the driveway buried in a snow bank. I started it today thinking the cold weather, just above freezing, would bump up the pressure. Instead, it would barely come up above zero so I shut it down. Now I am even afraid to turn it around so it is facing the garage. I may be stuck working on it were it sits.

    My guess is the pump pick up o-ring or maybe the pump. Not too worried about bearing wear since it happened so fast. Before I do that I wanted to check the following.

    The gauge tipped below zero then goes up like it should when starting so I doubt it is the stepper motor. Has any body ever had this happen like this and it only be the sensor?

    My truck is a 2006. Is it true that the lifter filter screen under the sending unit was not used until the 2007 and up motors (and earlier non-Yukon models) with the Displacement on Demand?

    I had done an oil change 2 weeks earlier with a house brand cheap filter. I usually use Fram filters. I have heard of similar problems with filters collapsing. Any chance of this?

    Any other thoughts based on experience before I drop the pan?
     
  2. Sasquatch

    Sasquatch Full Access Member

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    I would try replacing the oil pressure sensor first. The same thing happened to my oil pressure and i changed the sensor and it fixed the problem. If i remember correctly it only costs around $30-40.
     
  3. David Smith

    David Smith Full Access Member

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    I literally just went through this exact issue. I fixed it yesterday actually. I replaced my sensor and it did nothing. Mine ended up being the o-ring. It is a very easy job. Slightly more difficult/time consuming if you have a 4WD.

    I am not sure about the sensor filter in an 06, but maybe buy one just in case. I THINK they put those filters in on the AFM engines. Just my guess.

    If the gauge is responding to you hitting the gas, I would assume the gauge is reading fine and that the sensor is probably fine.

    After going through this entire ordeal, I would just start with replacing the o-ring. It was actually easier to me than replacing the sensor. The sensor is very difficult to get to.

    I swapped out the o-ring in 1 hour on a 2WD.
     
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  4. Musicars

    Musicars Member

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    I always thought when the sensors went bad they usually went to zero or 80. I know a lot of guys do the sensor first. I try not throw parts at a problem but you be right and this could be the issue. Did your gauge actually show pressure and move with RPM like mine is/was?
     
  5. swathdiver

    swathdiver Full Access Member

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    Yeah, that reads like an O-ring to me too. A failing sensor would not drop down in steps like that, well, highly unlikely.
     
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  6. Musicars

    Musicars Member

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    I have a Denali with AWD. At first I was scared to death to have to drop the pan because I had heard the front differential had to come out. But I have seen videos where guys had just taken the bolts out on the right side and left the diff sag and had enough room to pull the pan. Still not looking forward to doing it in a driveway next to a melting snowbank if that turns out to be the problem.

    I do have a leaking right axle seal so if I drop the pan that would be a good time to do that too. Still not looking forward to it. Terminal winter here in Minnesota is not helping. I never thought I would look forward to mowing the lawn.
     
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  7. mattbta

    mattbta Full Access Member

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    Goes without saying, but while you're in there for the o ring, put a new pan gasket on too. Did mine on my 04 2wd last weekend. My oil pressure was fine but did the o ring while I was doing the gasket to fix a leak. Was surprised to see my overall pressures go up 5-8 PSI over the entire rpm range....even though I barely showed under 40 at any time before the new o ring.
     
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  8. Rocket Man

    Rocket Man Super Elite Member Supporting Member

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    Try a new filter first just in case. It seems odd that you just put a cheap filter on 3 weeks prior. You don't need to drain the oil to do it so that's a super cheap experiment. Yes cheap filters have caused low oil pressure. I dropped the pan in my Denali by pulling the bolts for the front diff and forcing it down as I pulled the pan. It fits barely but it's not too bad. When installing the pan, use new pop rivets that hold the gasket in place so it doesn't slip.
     
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  9. Sasquatch

    Sasquatch Full Access Member

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    When my sensor went bad it read a little lower each time i used the truck. I`m not saying anyone is wrong but i would certainly rather change that sensor before changing the o ring.
     
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  10. swathdiver

    swathdiver Full Access Member

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    Boy, that went right over my head, good call Mark!

    Thanks for the information Ted. I reckon that a failing sensor is not unlikely to behave that way now!
     
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