i have a 99 s10 zr2 4x4 its got a new oil pump and sending unit. it starts up and idles out great ans sounds good, no noise, no smoke. when it get up to normal temp 195, i lose all oil pressure. then i can hear a light bottem end sound. i can shut it off after it cools down. i start up again and it sounds awsome, untill it gets to normal temp, then the sound will come back....

 

sounds like worn bearings to me, mileage?

check pressure with a test guage

 

What is your oil pressure at idle ...650-750...when cold?