ZERO OIL PRESSURE! HELP!

[Matthew Keeney]

Ok, Im working on an 03 Ram with a 5.7. The issue is random total loss of oil pressure while driving. At startup it has around 55-60 psi and drops to 45-50 after it warms up. Start driving and anywhere from 1 to 15 minutes later the gauge will drop to 0 psi and the check gauges light illuminates. So I put a "T" with a mechanical gauge in and it agrees with the factory setup, Zero oil pressure. But here's the part that troubles me, if you shut the engine down and immediately restart it, the oil pressure is back and normal and will stay for another 1-15 minutes but usually on the low end of that.... I'm thinking that the filter bypass could be opening up and letting the "dirty" oil around the filter and sending unit... Any ideas before I get surgical?

 

[chrisp2493]

Something stupid, but check the oil level. There is no “low oil” warning. When I had some issues and had low oil, every time I went around a corner, I would lose oil pressure, the garage would just drop.

 

[Matthew Keeney]

Yea, that's pretty much standard procedure. But thanks for the tip

 

[Eric Sabin]

I am having similar issues. Mine is on start up. It happened a few times in the past but for the last couple days it has been every morning on the way to work and when i leave work. Basically cold starts. When i shut it off and immediately start it back up, it builds pressure like normal. From what i have read i may have sludge restricting the pick up tube. Maybe related to your issues as well.

 

[Casper]

While it could be the filter bypass you should still have some system pressure.

I would also check to ensure your oil pan, or oil pump suction and screen isn't full of sludge. When the engine is off, enough oil pools around the oil pump pick up, and the sludge that is sucked artificially raises viscosity, but once the galleries are full and the oil is warm there isn't enough free flowing oil volume around the pick-up for the oil pump to suck oil. While examining your sump, check the oil pressure relief valve for any irregularities that could cause it to stick open, and make certain the pick-up tube has no gaps that could suck air.

As a contrary idea and far less likely, your pump is failing and once the engine warms the viscosity of the oil drops to the point the leak-by is preventing the pump form moving much oil. Not as likely as the sludge issue or pressure relief above since these are reasonably reliable pumps and internal wear like that would mean some real abrasion or metallurgic failures.

 

[Demon-HeMi]

While it could be the filter bypass you should still have some system pressure.

I would also check to ensure you're oil pan, or oil pump suction and screen isn't full of sludge. When the engine is off, enough oil pools around the oil pump pick up, and the sludge that is sucked artificially raises viscosity, but once the galleries are full and the oil is warm there isn't enough free flowing oil volume around the pick-up for the oil pump to suck oil. While examining your sump, check the oil pressure relief valve for any irregularities that could cause it to stick open and make certain the pick-up tube has no gaps that could suck air.

As a contrary idea and far less likely, your pump is failing and once the engine warms the viscosity of the oil drops to the point the leak-by is preventing the pump form moving much oil. Not as likely as the sludge issue or pressure relief above since these are reasonably reliable pumps and internal wear like that would mean some real abrasion or metallurgic failures.

this right here, i had the exact same problem on my truck a long time ago, id have fine oil pressure and if i got on it at all id start having issues, i ran a chemical oil flush through it and when i drained it out, i watched some sludge come out of the oil pan drain, after that i never saw the issue again