Oil Pump Problems?

I'm the new guy. I've bought my 91 explorer in 1995 with 90k miles on it. It now has 200k miles on it.

So here is my question. Back in 2001 my oil pressure gauge started fluctuating. Mostly it would start to fluctuate when the car was warmed up and the engine RPMs were below 900 while in gear. However it would stay in the normal range. A few years later it started to drop to zero when warmed up and in gear. So I went from 10w30 oil to 20w50 in the summer months and the problem went away. However, being in New England the winter does not really allow me to run 20w50 in the winter because it has had cranking issues, so I would normally run 10w40 in the winter with no problems.

Well, the problem is now to the point that even in the winter, running 15w50 the oil pressure will drop to zero when in or OUT of gear below 800 RPM once the car has warmed up (5-10 minutes).

I'm guessing with 200k miles, the oil pump is probably on it's last leg. The engine was replaced with a reman'd short block at 150k miles but after looking over the records the oil pump should be the original.

So, anything else it may possibly be before I go digging into the bottom of my engine? Also, anyone done this replacement before? How involved is it? I am no stranger to working on cars, but usually I only work on older cars (I've restored and modified a few old mustangs) and leave the newer ones to real mechanics for my fear of electronics. Any tricks I should know about before I start this?

Slade

First thing I have to ask is have you changed the oil send on the left front bottomof the engine? The oil pressure gauge works like the idiot light on or off, so I would recommend changing the sender and see if it doesn't correct your problem.

I know i bought one way back when to do it, but I don't think I ever go around to it. I'll give that a whirl. I definitely don't hear sounds of low oil pressure like hydraulic lifter tapping.

I guess that kind of answers my other question about whether the pressure gauge just reads an actual pressure or just "Pressure" or "No Pressure". My oil light and my check engine light never come on even while the gauge zeros out.

Slade

I think that will solve your problem. Good Luck!

I would pull the sender unit and put a manual pressure test guage on it to see if you are having a pressure problem first. I dout its the oil pump they will usually gernade and take some things out. Another thing you can do if you can get your hands on a factory ford service manual is to take a fluke meter and omh out your sender unit or at least compare it to a new off the shelf one.

I had the identical problem, fluctuating oil pressure, with my 93 at 125k. I did replace the sending unit, after market, and it corrected the problem. However, it returned about a year later. This time, on the advice of my mechanic, I replaced the sending unit with a Ford part. No problems since. Definitely try that first.

Well, it turns out to be the oil pump. I replaced the sending unit...same problem. Checked with a mechanical gauge...35 psi at 2000 RPM, 0psi at idle in park.

Anyone know what the ball park figure is to replace the oil pump at a dealership is? I was quoted $500-600, just want to avoid hidden expenses. I would do it myself, but at present, the ending suspension and drivetrain of my 65 mustang is laying across my garage and my engine hoist is MIA after I let my brother-in-law use it on his car.

Slade

Oil Pump swap!

I'm interested in what avenue you took with replacement. How long or How much did it cost you? I'm having that same problem right now in NH.