Q: Chevy 5.3l - Lost oil pressure, why?

Hello - since you didn’t appear to be leaking oil in a significant way (busted oil line, hole in the pan), I suspect that the oil pressure relief valve may have been stuck in the "relief" position. Some of the early 5.3l engines had trouble with this - galling in the pressure relief valve bore. Pull the plug, spring and ball out to be sure the spring hasn’t broken. Light tapping on the block may be required to release the stuck valve. Good luck!

Hi there. use a mechanical oil pressure gauge and check for oil pressure on the engine with the engine running. If there is oil pressure, then the engine is if but needs to have another oil flush for contaminants in the engine. If the oil pressure is at zero, then the oil pump has failed and needs replaced or the pickup tube has too much buildup and preventing flow to the oil pump, which will damage the oil pump. Even if a bearing failed, there will still be oil pressure. I recommend replacing the oil pump on the engine and cleaning out the pickup tube. The oil pump to your engine will be on the front of the oil pan and right behind the timing chain. You will need to remove the timing chain cover and timing chains to get to the oil pump. Then you will also have to remove the oil pan to remove the bolts that hold the oil pump in place. Then the pump can be taken off and replaced. Once the pump is replaced, the pickup tube is cleaned out, and new oil and filter is in the engine, start the engine and make sure that there is oil pressure. If you need further assistance with your vehicle, then seek out a professional, such as one from Your Mechanic, to help you with the oil light on and engine ticking noise issue.