97 5.7 low oil pressure fix?

[Donaven361]

Howdy y'all,

I'm having oil pressure problems, just wanted to see if there's anything else to do before I go and replace the oil pump.

No reason to believe the sending unit is reading incorrectly. It tracks how it's supposed to, doesn't bounce around. It's just after the engine warms up, and I'm at idle in drive or in park the oil pressure drops to 0. Soon as I give it gas though, the pressure returns.
My best guess is the pump has lost its low end efficiency since it has almost 400k miles on it.

What do y'all think?

 

[stutaeng]

400k?! Has it been rebuilt before?

Hook up a mechanical guage to check against specs. I'm thinking worn bearings. Change to heavier weight oil and keep running it. Or plan on a complete overhaul soon.

Drain the oil and look for glitter. Or send to lab for analysis.

 

[Donald Mitchell]

At 400k the bearings may have lost their efficiency.

 

[Schurkey]

Verify that the oil filter hasn't collapsed internally.

At 400K, I'd be more likely to believe the engine is worn out, not merely the oil pump. Lab analysis of the oil is an excellent suggestion.

 

[L31MaxExpress]

Oil pumps build pressure by pumping against backpressure. As bearing clearences open up the oil flows more freely resulting in lost pressure. You very well could have an oil pump bypass valve hung open, a plugged up oil pickup screen or even an oil gallery plug that has come out. My guess at 400K the bearings are worn and its time for a rebuild though. You can always put some 15w40 or 20w50 in it to possibly buy some time. Another viscosity improver that works very well is Lucas oil stabilizer.

 

[Jeepwalker]

It would be a good idea to rent a oil pressure test gauge (free) at Autozone or OReilly's. Remove the sending unit and try the gauge. It would be good to know exactly what you have for oil pressure. Best if you could get a gauge that went from 0-60psi. Gauges for higher pressures, don't read as accurately at their extremes. If you had 0 psi the lifters would be making noise. If you have 6 psi at idle (hot), that's still, believe it or not, enough to run it ..so long as going down the road it's running in the mid 20's and higher.

That engine has done really well to make it 400k miles. If you're going to throw on a new oil pump, you might consider treating that old girl to a set of new rod and main bearings at the minimum. Cam bearings if you have it out and apart. But if you were planning to do the pump install with engine in the vehicle, then, I see where you're coming from. Put a higher volume unit in (obviously). Good luck. Let us know how it goes.

.

 

[AuroraGirl]

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Engine Oil Pressure Sensor
Part# 19244500

Per Veh: 1
Years: 1996-1998