Low Oil Pressure at Idle When Warm

Discussion in 'Engine & Drivetrain' started by Austen Leach, Jan 17, 2020.

  1. Austen Leach

    Austen Leach Member

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    I have a 2004 Tahoe with a 5.3 flex fuel engine and I've started to have low oil pressure issues at idle when hot only. When I start the truck cold the oil pressure is at 40psi and will go higher whenever I touch the accelerator. But as the temperature starts to rise the pressure will slowly bleed off. At 210 degrees the oil pressure is at 20psi and will go up to 40psi at about 1200 rpms. I've already replaced the oil pump pickup tube o-ring thinking that was it and it didn't solve my problems. Anyone have any ideas?
     
  2. SnowDrifter

    SnowDrifter Full Access Member

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    Have you hooked up a mechanical gauge to read oil pressure?

    How many miles on engine?

    What oil are you using?

    Is this a new symptom?
     
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  3. PNW VietVet

    PNW VietVet Full Access Member

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    First: Welcome to the forum.

    Second: Like Chris said, supply more info to help us help you. Plus, any recent work to the engine besides the o-ring replacement? Are there any different/strange engine noises related to this oil pressure drop?
     
  4. Austen Leach

    Austen Leach Member

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    I have about 136k on the odometer, I’ve been using Castrol Edge 5w-30 since I bought the truck when it had about 115k on it, it is a new symptom that started here recently, there are no engine noises at all (knock/flatter/taps), and there has been no other engine work done besides a tune up. I don’t have access to an actual oil pressure gauge to verify but I thought that the 5.3s had a real time gauge and if the sensor went out it would either show zero pressure or max?
     
  5. PNW VietVet

    PNW VietVet Full Access Member

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    We are all of the opinion that an actual oil pressure gauge should be attached to where the sensor is and get a reading from a known good pressure gauge and because it is a PITA to remove the sensor, replace it when you take the gauge off.
     
  6. Austen Leach

    Austen Leach Member

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    Give me a couple days and I’ll report back with an update. Thanks!
     
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  7. PNW VietVet

    PNW VietVet Full Access Member

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    Great. Make sure you get the pressure at start up when cold, watch as it warms up, pressure at idle when warm and then at 1200-1500 rpm and watch what it is when you throttle it quickly one time. Don't have to hold the accel but just a quick throttle increase. Some here may not agree but I like to do the complete range of cold/hot and idle/rpm differences.
     
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  8. swathdiver

    swathdiver Full Access Member

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    Austen, what oil filter are you running presently? Do you always use this filter?
     
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  9. Austen Leach

    Austen Leach Member

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    I was running a Wix like I had been since I bought the truck when the issues showed up. When I swapped the pickup tube o-ring and changed the oil I replaced it with an AcDelco because I had read that the oil filters could be causing an issue with low oil pressure
     
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  10. swathdiver

    swathdiver Full Access Member

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    After my engine's oil had 4K+ miles on it, the pressure when hot, stopped at a light in gear, would also drop down to about 20 psi. I was using a Mobil 1 filter and have since switched off to K&N and pressure has returned to normal. I have no experience with WIX and stopped using the ACDelco E-Core filters, change your filter to something else and see, leave the old oil in there save for what you need to top it off.
     
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