I have a 1995 F-150, 5.0L V8

Oil pressure guage will, after driving for a while, start to fluctuate then drop to 0psi.

If I shut off the engine, and restart, it will usually come back to full pressure for a while.

I drove it like this for a few days, (engine temperature never got higher), but now it's making a rattling sound.

Question: Is the problem most likely the oil pump, and does this new noise mean I've already wrecked the engine?

Thanks for any help anyone can give.

 

Since you didn't state the mileage.

I would suggest that you pull the oil pan and have a look see.

If you, or previous owners, weren't loyal with the oil changes you're probably slugged up.

If you have a rattling, well sounds like the damage is already done and the bottom end is going away.

Good luck...