I own a 5.3 2007 Avalanche. It has 160k miles. When it is first started it holds approx. 40 pounds of oil pressure, once it warms up, when idling it drops to 0 and the bell goes off. If I give it a li

Hi. I have a recently acquired 2007 5.3 Avalanche with 215K miles with 15K on a rebuilt engine. Supposedly it had fresh fluids all around so I had planned an oil change. B4 that change - I had the oil pressure sensor light go off on my morning commute - telling me to stop the engine due to "No Oil Pressure". Since my temps were normal on the gauge and no lifter noise, I assumed the Oil Pressure Sensor was bad. More interestingly was that when the engine was shut down for a time, it took about 10 minutes for the warning to crop up - something to do with the oil heating up and something (I'm not sure happening with the sensor). So at the earliest opportunity I changed the oil to Pure Synthetic (Schaeffer 9000) 5W30, Mobil 1 Oil Filter and that took care of the warnings I was getting. I am keeping track of mileage and keeping an eye on oil level - as we all should. I'm not sure if it was debris that cleared out which I would doubt given that the mechanical nature of the setup or if it is sensitive to oil viscosity/age (i.e. If you do need to change the sensor - there's several videos out that show how to do it without removing the intake. I know as I was reviewing this to change my sensor. Keep in mind that if you are going to change the sensor - you may as well change the screen filter in the oil supply line that goes to it. I have driven about 500 miles since the oil change with no "warnings". My pressure when running ranges from 45 to 55 psi and drops to about 20 psi when idling warm. Good Luck.

My problem was fixed with the gauge cluster and oil sending unit. I had good oil pressure at idle cold, and would slowly drop to zero and only come off of zero when revving hard. No engine noise present and ran fine. I have been running about 10k miles since with no issue after changing the cluster and sending unit. What I'd suggest is connecting an oil gauge to the sending unit port and measuring the oil pressure yourself. If it's indeed low in warm idle conditions and stays that way, then you need to dig mechanical. Most people have solved the mechanical side of this issue with the oil pick up tube o-ring.