carlosbu

I have a 2008 Chevrolet Tahoe Z71 4x4 with 170k miles. Its been a great vehicle and we plan to keep it till the wheels fall off! Last winter when up in Colorado I went to start it and the oil pressure fluctuated back and forth between 15-40 until it warmed up. When I revved up a little of course the oil pressure went up. When it was warm it idled at 30 psi and when driving 40psi and above.

When back in New Mexico I took it my mechanic and he said that the oil sending unit and gauge were fine as he checked them through the computer. He did not check it manually. It continued to fluctuate during cold startups but never to the point of throwing a check engine light, low oil pressure light, nor did I hear any engine knock. Through this Spring and Summer it was fine at startup. Now its getting cold and its starting to fluctuate again on cold startups. I asked another mechanic friend about it and he says its the sending unit....that he sees them a lot with 150k mile 5.3 and 6.0 gm engines. He said its not the O-ring.....I am at a lose as with the research that I have done its looking more like the O-ring on the pickup tube.....

Any input would be greatly appreciated.

SmokChsr

That's exactly how it will act when the O ring is first going bad. Wait until it gets cold in your area and you'll see it start doing there as well. Once it starts doing it if you want confirmation pull the dipstick if you see air bubbles in the oil on your dipstick it's confirmed that the "O" ring is going bad. If you let it continue you will start to get tapping in the top side of your engine.

TWard

I have a 07 Suburban LTZ and had a similar issue at 110k. There's a screen in front of the oil sensor that can get clogged. I ran a can of Seafoam in the crankcase for about 100 miles and changed the oil. Never had the issue since. In fact, I run Seafoam before every other oil change to make sure it never comes back.