Weird oil pressure issue

[bartgillam]

I was driving down the highway roughly 75mph and my oil pressure gauge started rapidly bouncing up and down. I got off at the exit and as I came to a stop at the light it continued to bounce. I pulled to the next red light and it dropped down to no pressure. I heard the engine start ticking so I know it had no oil going in. I shut iktnt off andand when light turned green i cut it back on and the pressure was fine. Added 2 quarts of oil and everything was running normal. On the way back home it started bouncing again and I just pulled off and had to coast into the gas station with engine off as it to could hear it's ticking from no oil again. What could be the issue? The pump works...i assume..because it runs after I cut it off and back on few minutes later. Any ideas?

 

[BrooklynBay]

Unscrew the oil pressure sender, connect a mechanical oil pressure gauge, then see if the same issue occurs. The oil pump might be starting to fail if the mechanical gauge does the same thing.

 

[2000StreetRod]

clogged oil returns?

The oil return passages could be clogged and the oil is forced to pool in the heads eventually starving the oil pump. If you have the SOHC V6 a cassette guide could have broken and the pieces are blocking the oil pickup tube screen.

 

[crunchie_frog]

The oil gauge is a pressure switch, either on or off. If you heard ticking after the light came on, it could be the oil pick up tube is blocked/plugged and the oil switch is working. I think I would try replacing the switch, even though it is likely good because if it is I think the next step would be pulling the engine to see what is going on with the pump.

 

[Robman]

I doubt the "switch" is bad ... if the gauge goes dead and your engine starts ticking, I'd say the gauge works.
To lump in with the above mentioned causes, can't rule out a buggered up oil filter either.

 

[Runnin'OnEmpty]

...I was driving down the highway roughly 75mph...

...can't rule out a buggered up oil filter either...

I agree with Robman; the highway speed and associated high oil flow and
pressure could possibly have collapsed the filter media. I've seen it happen.

 

[Macgiobuin]

I had a similar problem with a '93 E150 van 4.9l I6. After a few miles with a warmed up engine, the light would come on. I stopped, let it sit and it would be okay for about 20 miles then again, all with full oil crankcase. I took down the oil pan and saw that the sump screen was clogged. Bad. I cleaned out the sump and screen, pressure washed the sludge caked head while the pan was off and the plugs were out; let it sit for a day, sprayed WD40 onto the journals and into the cylinders, activated the starter for a minute or so, then put the thing back together. Saw that the car had a Technical Service Bulletin on it. TSB described the sludge problems that occurred on that engine, recommending that customers replace the PCV valve with a different part number. Problem solved, but what a hassle. Anyway, you probably have a clogged sump. When you shut off the motor, the muck falls to the bottom of the pan after a few minutes and you can run again til the sump is clogged again.

 

[koda2000]

If you have the SOHC V6, it's very possible there are broken plastic pieces of timing chain cassette in the oil pan that are blocking the oil pickup screen, These pieces are curved and to a great job of surrounding the circular shaped pickup. If you have a 2WD it's really easy to drop the lower oil pan to check this and clean out the broken pieces. If you find plastic pieces in the pan it doesn't necessarily mean your engine is about to explode tomorrow, but you probably are hearing some degree of timing chain rattle, which will eventually lead to it's demise.

 

[delexploder]

97 mountaineer would be 5.0 , could also be the pump drive ie the cam syncro

 

[koda2000]

97 mountaineer would be 5.0 , could also be the pump drive ie the cam syncro

I didn't realize the Mountaineer was only available with the 5.0L V8 in '97. Beginning in '98 you could have gotten the 4.0L SOHC V6 in the Mountaineer, which is odd as the SOHC engine was available beginning in '97 and you could have gotten a '97 Explorer with the 4.0L OHV, 4.0L SOHC or the 5.0L.