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Hello, I have a 2005 GMC Sierra SLE 5.3L 2wd with 271k. I have recently started to experience issues with holding oil pressure at idle. OPS is functioning correctly and external pressure gauge has confirmed my on dash readings and I’ve always used 5-30 as per the manual. At this point I am now under the impression that my pressure relief spring is faulty or is partially stuck open by sludge… Given I have exceptionally high mileage but have changed the oil religiously since it was purchased brand new in 05 I know there will be some loss of pressure from normal wear but given the symptoms and my diagnostics I believe that I can now condem my pump. Has anyone ever changed the oil pump
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The oil pump is not what creates oil pressure! Clearances in the engine do.
What does your oil gauge read at idle when it seems really low? I know older GMC truck engines the concenses is 9-10psi per 1k RPM, is considered fine.
There’s a known problem with an O ring in the pump itself. A local GM dealer should be able to point out the TSB on it and have a new specific O ring. The original will be red and the replacement blue, or vise versa.
I knew I was walking into the lions cage with this post. I had planned to add a video with this post step show my issue. Yeah understand the pump does not create the pressure. My gut feel is that my pump is not moving the volume needed to create the pressure as this is an intermittent problem. With the external gauge not showing rapid fluctuations I’m lead to believe that either I’ve got a clog in my screen on my pickup tube, a worn out pressure relief spring, or now a bad O-ring from my pickup tube to pump. See the attached picture for my pressure reading at idle when this gremlin shows its ugly face. On more than one occasion it has displayed the low oil message and sang me the song of its people (warning chimes).
Well, it’s only been 7 months but I finally got around to changing my oil pump yesterday. I had also ordered a timing chain because going that far it was low hanging fruit, it had stretched and had an insane amount of play in it. Changing the pump and pickup has solved my pressure issue. The pickup o-ring was rock hard due to all of the heat cycles over the last 10 years and there was a very minimal amount of sludge and gunk in the oil pan when I got it pulled off. I was unable to perform an autopsy on the pump because the wife wanted me to get done with the job…
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