2.5L ('98-'01) Oil Pressure

[Xyke]

What is normal operating oil pressure, both cold and running temperature, for '01 2.5L with standard trans? I have an erratic, bouncing needle indicator oil pressure gauge, when engine is at normal operating temp. Have replaced sender switch twice already.
I think I read somewhere, that the pressure sender switch was an "On/Off" switch, that would show normal range when oil pressure is 7lbs. My gauge needle bounces from "normal" pressure setting to nearly zero pressure. I want to install under dash, separate, pressure gauge to monitor, but it would help if I knew what is "Normal" pressure. If pressure is truly erratic, I'll pull engine and check pick up tube, and/or replace pump.

 

[RonD]

Yes, 1989 and up Fords use an oil pressure switch, on/off, 5psi is the cut off

Could be a clogged passage at the switch
Disable spark, unplug both coil packs
Remove switch
crank engine over, oil will come out of the passage and any clogs
Clean it up, lol
DO NOT put tape on the switch threads, the threads need to be grounded to the engine for the switch to work
Install switch and see if gauge is still erratic

The switch is the Ground for the oil pressure gauge, with no ground gauge reads 0 with ground gauge reads 1/3 to 1/2 it varies by VOLTAGE not oil pressure, so the ground is important

If oil pressure was actually dropping under 4psi then valve train would start to make "ticking" noises, so if you haven't heard that then the bouncing needle is not a true reflection of oil pressure


You can add a "real" oil pressure gauge by adding a variable oil pressure sender in place of the switch and a gauge
If you want both the dash gauge and the "real" gauge then you will need a setup like this: https://www.explorerforum.com/forums/attachments/parts-jpg.83284/

A "T" coming out of the current oil switch location
The larger unit is called a PS60 oil pressure sender, and works with most 3rd party electric oil pressure gauges
Or you can use a fluid oil pressure gauge and run an oil tube into the cab to the fluid pressure gauge

If you don't want the dash oil gauge to work then no "T" is needed, just install what you need for the type of gauge you chose to use

General rule of thumb for WARM oil pressure is 10psi per 1,000rpms
So at 700rpm idle 7psi would be expected, cold oil would be above 10psi most likely
40psi at 4,000rpm
Usual cut off point is 40-50psi at high RPMs, the pressure relief valve on oil pump starts to open to prevent too much pressure

Oil pressure is like human blood pressure, too low and too high is bad, lol

Oil pressure is the oil the engine CAN NOT USE at that moment
The oil pump creates the flow of oil thru the filter and then out to the oil passages in the engine
The oil that CAN NOT BE USED backs up in the main oil passage and creates the "oil pressure" you see
As RPMs go up the oil pump flow increases, but the bearings and valve train flow doesn't change much, gaps and holes are still the same size, lol
So oil pressure goes up with RPMs because flow IN increases but flow OUT doesn't change that much

You want pressure above 5psi because of gravity, lower pressure won't push the oil up into the valve train fast enough
And you want pressure below 70psi or the oil will squirt out too fast causing bearing washout, causes "dry spots" on bearings so they overheat

 

[Xyke]

Great reply, full of info.
I have been thinking of checking/removing teflon I wrapped onto sender unit, but the point & procedure you made about possible glogged passage is very much worth the effort before pulling engine. Thank you for the exceptionally speedy reply. I'll do a follow up post. Thanks.

 

[Xyke]

Follow up on erratic, bouncing, oil pressure switch:
Evidently there are two types of oil pressure switches. One for a light on your dashboard and another for a mechanical gauge on your dashboard. Not being absolutely sure which one was installed on my engine, I replaced it with a Motorcraft oil pressure switch for mechanical gauge, and that ended the erratic, bouncing gauge needle. Hope this helps someone else with a similar problem.

 

[RonD]

If its a Yellow oil light that's for Oil Level in the oil pan, there is a one wire sensor on drivers side of oil pan, it will trigger the oil light if oil level in the pan gets low
It can also come on if you are parked at a sideways angle with drivers side higher than passenger side, because oil is sloshed over to passenger side uncovering the oil sensor

There is only 1 Oil Pressure sender on Rangers

 

[WarHawk-AVG]

I would say next oil change, put a pint of seafoam in the oil...let idle for 15-20 min...then change oil and filter...might have buildup of gunk in the system
If the passages are clogged up...oil pressure will go all wonky
Or...worse case...the bearings and such that maintain oil pressure are so worn out...when it warms up...oil is just squeezing past so fast it can't maintain the flow to maintain pressure