No oil pressure

[dknain]

1997 Mountaineer 5.0 2wd. Bought it a few years ago and had fluctuating oil guage. Pulled the engine and found the pan caked with gunk. Replaced the oil pump and cleaned the pan. Now 3 years and 20000 miles later it started again. Checked the inside of the pan for gunk, replaced the sending unit,and the guage. Still starts with good pressure then drops to 0. Pulled the sending unit and replaced with mechanical guage which started at 30lb then after 2 minutes it gradually went to 0. The engine still runs smooth without any bad noises but I don't let it run long once it hits 0. Pressure relief valve ? or what ? Help !!

 

[dknain]

New development. Put a quart of Rislone in it and it ran 30 minutes and never went below 7 psi. Shut it down for an hour went back and started it and it ran for 30 minutes and pressure stayed at 10 psi. Maybe a good flush is all I need

 

[Vic_Ferrari2002]

I hope for your sake that's all it was and your problem is fixed. However I have found that when the oil pressure on a cold start is good and drops off as it warms up usually means that the bottom end bearings are on their way out.

 

[dknain]

Hope not. Keeping my fingers crossed. Just tried it again an it maintained 15psi. Also before when it was 7 psi the pressure dropped a little with increased rpm. Now at 15 psi it went up to 20 psi when I ran the rpm's up to 2500

 

[96ex5.0]

Don't rev you must have 10 psi for every 1000 rpm, or you risk spinning a bearing. Would try a good flush then run a thicker oil 10-w40, I'm hard on mine and do a lot of high rev off road stuff so I run motorcraft 15-w40 or 20-w50 in the summer 10-w40 winter. Yes that may seem excessive but my bearing look great for having 180k miles.

 

[2000StreetRod]

restricted oil return?

If the return oil flow is restricted it can collect in the heads and galleries eventually resulting in a starved oil pump. It takes multiple engine flushes to eliminate caked sludge.

Sludge build up often is the result of a low temperature or stuck open thermostat.