joeinblueout4u

Like the title says, I've got some funky oil pressure readings going on. When my engine is cold, and more common after a fresh oil change, my oil pressure goes to 80 psi on start up, then after 5-10 seconds of idling, the pressure drops to just above the zero pin, the Check Gauges light comes on, and the pressure stays like this for 20 seconds or so at idle before jumping back to 80 psi.

The engine does not knock or rattle when the pressure shows to have dropped, so I am guessing it may be a sending unit, but since it happens more often with fresh oil and colder temperatures, I wonder if the sending unit is the issue. When the engine is fully warmed up, oil pressure is 35 psi at idle and is at 50 psi at highway speed. The engine currently has 235k miles and has been doing this off and on since we bought the truck with 175k miles.

The question is this, bad oil pump or bad sending unit? This is a stock 2003 Ram 2500, 250 Hp engine.

Oil is Rotella 15-40 and filter is Wix, as always.

-Joe

BigIron70

I would first do a mechanical oil pressure test, if the oil pressure does not drop or fluxtuate then replace the oil pressure sender. If it does drop then you have internal issue with pump, or relief valve.

joeinblueout4u

Sounds like a plan. I need to get a mechanical gauge, for piece of mind if nothing else. I was reading a thread from back in September that essentially said the oil pressure gauge in the dash is unreliable at best.

-Joe