My girlfriends '98 Mustang 3.8 (175k) ran hot (but not yet pegged) after it blew a head gasket.
Afterwards I noticed that the oil pressure would sometimes fall instantly, or quiver. At first I thought this had to be the gauge or sensor because it moved so quickly, and looking into oil filler, you could see oil flowing. But after a short while you could hear the valves tapping (and turning off the car and back on would restore pressure). It appears to me that the sensor is at the pump, instead of at the end of the oiling line.
There was a great deal of sludge in the motor, a cup or two that I removed by hand. I'm thinking the hot engine must have loosened some up and this is clogging the oil intake.
So, I've run a can of quick flush and cycled some used filtered oil back through. It's much much better, but now and then I still see a drop sometimes.
The pan appears to be a tough job to get off.
Suggestions? Or do I have this wrong.
Jeff