I have not posted in a while but today after my truck had sat for (6) hours or so in mid 40 degree temps I started her up. I immediately noticed the warning "Low Oil Pressure" warning in the dash. I also confirmed the oil pressure gage was reading 0 psi. I shut her down right away. At this time there were no abnormal noises. I did some searching on the net and went back out to look at sending unit behind the intake. Nothing seemed abnormal so I decided what the hell, lets start her up again. The same thing happened with the warning and the gage. I slowly revved the engine to see if the gage would move without luck. After a few minutes of idling, I noticed the top end getting a bit more noisy. This went on for a minute or so and then all of a sudden I had oil pressure and the top end quieted right down. I went for a hard ride and it would rev to 6200 no problem. I know something is probably wrong but what would have caused this. It seems as though the top end is a bit nosier than before but its hard to tell. Any help would be appreciated.

 

Sounds like the pressure relief valve in the oil pump may be sticking...