Low oil pressure

[neptune1230]

Cold start- engine idles @ 500 and oil pressure is 0. If I increase the rpm to 700 or higher I get 40+ on oil pressure.Once I lay off the pedal and rpm drops back to 500 and oil pressure goes to 0.

Warm engine- it idles @ 500 but the oil pressure stays around 20. As rpm goes up so does oil pressure, just like it should.

I am using 5w30 castrol syntec.

Any suggestions would be greatly appreciated, thanks

 

2001 yukon 4wd. 5.3L

[GM-Tech]

I'd stick a mechanical gauge on it to see if the what the pressure really is.

[neptune1230]

I'd stick a mechanical gauge on it to see if the what the pressure really is.

 

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I can hear the lifters clacking when the pressure is 0, the clacking goes away when the oil pressure rises. I have changed the oil pressure sensor, it gave me better readings but did not solve the problem.

[GM-Tech]

I can hear the lifters clacking when the pressure is 0

 

Sounds like it's definitely low then. Odd, it usually works the other way around. Good pressure when cold and the oil's a little more viscous and pressure dropping as it warms up.

 

Doesn't sound like a clearance problem. Most likely, pressure relief valve in the pump is hanging up. That'd be the first place I'd go.