Low Oil Pressure (Gauge Goes Up and Down)

[Sweersa]

My 2005 V6 4.0 XLT 4x4 today threw a Check Gauge light, and at the same time the oil pressure gauge dropped to the bottom, and the Low Oil Pressure warning was displayed in the message center. After about 30 seconds or so, the dummy lights would go away, oil pressure gauge would go back to the middle position where it normally is, and after about ten or so seconds the oil pressure guage would go back down, dummy lights back on with message center warning of low oil pressure, and the process repeated until I got home. I shut down the engine to check the oil level (seemed fine) and restarted it, it idled fine for the 5 minutes I ran it. I also gave it some gas to increase the RPM while running in park in the driveway and everything seemed ok.

I have just under 300,000 miles on this beast. Last changed the oil 2,400 miles ago (I've always run 5w30 conventional) and the dip stick had oil on it. I plan on changing the oil and filter tomorrow morning. I typically change the oil every 2,500-3,000 miles, as this vehicle has exhibited loud timing chains for years.

It seemed to drive and sound fine (as fine as a 3rd gen Explorer with 300,000 miles) throughout these events.

Any thoughts on what it could be? I realize at this mileage, and age, it could be anything.

 

[Rick]

My guess is a bad sending unit, or connection at the sending unit

 

[Sweersa]

Thanks for the lead! I'm going to pick one up today. Cheap enough, and the job doesn't look too bad. I'll probably get around to it next weekend.

 

[Sweersa]

Replaced the sending unit / pressure switch today. The job wasn't half as bad as I thought it was going to be. Jacked the driver's side up, removed the front driver's side wheel, and the forward inner wheel well for access, and it's almost a straight shot. Used a 21mm deep well socket with swivel and extensions. Wiring harness was also easy to remove and put back on, just need to squeeze the clip area to release.

My 23 mile test drive today was successful. I'll be a little more confident of the repair after numerous additional trouble-free trips.

This is what the old unit looked like: (Not sure if OEM, but I replaced it with a Ford Motorcraft part)

This is a view from the front of the new unit installed: (If you look closely, you can see the little Ford oval on the flats of where the socket goes over)

I also changed the engine oil and filter. No oil came out of the hole where the unit is installed in, probably because that side of the vehicle was lifted on jacks during the job. Hopefully that's the end of that story! Thanks again for the help.