oil pressure/engine noise
I have a 1999 Ford Ranger (two-wheel drive, 138,000 miles). Twice in the past year I have had this happen: I notice truck is running very loudly/rough, and notice the oil pressure gauge shows no pressure. The first time, I pulled over, had it towed. At the service station they started it up, gauge was normal. I took it to the dealership, they replaced the sending unit, could not explain why it might be running rough. Today: same thing: gauges normal when I left home, and hour later I notice it running rough, gauge says no pressure. Pull over, turn it off, restart: still no pressure. Turn it off and let it sit 15 - 20 minutes, start it up: gauge is normal, runs smoothly.
What do I have them check next?