Hey Ranger Team,
Subject is a 2002 w/ 3.0 @ 196K
So just a week ago I started seeing the oil pressure dropping out per the 'gauge' when idling at a red light after it's all warmed up (not when it was cold). Bouncing a ton and sometimes just dead on the peg. I know it's just a switch so honestly that's even more concerning it's supposed to be like 6PSI I think? Haven't driven it since the two drives out and back to work.

On clean 5W-20 (<500 miles since changed) I threw an oil pressure gauge on at the switch port and saw it cold go 50+ while it was warming up (~900-1100rpm). If I revved it a bit while cold it would hit 60 max (relief pressure?) Then slowly drop to about 11-12 while idling in park after 30 minutes and fully warm.
I'm just now thinking I probably should have put it in gear to see what that pressure was as that's a bit lower RPM than when in park. But I didn't do that so here I am.
I just switched out the filter and oil to a 10W-30 and tested again. 'old' oil looked clean and normal, no sparklies or anything I could see different than all the other changes I've done on it. had it since 2005 I think with 30K.

Run Time - Oil PSI - Notes
0:00 - 53psi - Cold start
0:03 - 48psi
0:08 - 36psi - Normal Idle
0:11 - 24psi
0:13 - 22psi
0:17 - 17psi
0:25 - 15psi
0:35 - 13psi
0:42 - 12psi
0:50 - 12psi

Once hot I did some checks at different RPMs as well with the fresh 10W-30
RPM - Oil PSI
690 - 12psi (idle)
1330 - 28psi
1500 - 33psi
2000 - 40psi
2500 - 45psi
3000 - 48psi

Note that my test pressure gauge is new/unproven. I've got an electrical gauge to hook up as well, but there were complications with the sending unit not fitting so I need to run a small extension to split for the switch and the gauge sender. Then the heater coolant line broke at the tee and sprayed me down so that's gotta get replaced before I can do any more checks.

So my questions:
What should I realistically expect at 196K for oil pressure?
Aside from adding in an actual gauge (working on it) is there anything else I can do/check at this point? Would have to take it to a shop to pull the pan and get to the pump as you need some kind of hoist/rigging and I just don't have the space or time to do that.
Is this the 'sell it while it's still running' kind of thing or could this be ok for another chunk of miles? I only drive it one round trip a week ~30 miles typically.

Thanks for any insight and help,

 

Oil pressure is Back Pressure, so its the oil the engine CAN NOT USE at any given time/RPM
Generally speaking anything above 4psi can over come gravity to get oil to upper engine, valve train
Ford's oil pressure switch is set at 5.5psi, so gauge shows 0 under 5psi, and gauge goes up at 6psi, on/off setup

The oil pump provides more oil flow than the engine can use, by design
Bearing gaps are small as are valve train holes, which causes the oil flow from the pump to back up in the main oil passages which creates the "oil pressure" we see
As the bearings get worn the gap increases so more oil can pass thru so back pressure goes down a bit

General "rule of thumb" is minimum 10psi per 1,000rpm is good oil pressure
So at 700rpm idle with warm oil 7psi is good for high mile engines

So your pressures are fine, bearings are being cooled and valve train lubricated just fine, so fine to drive it as much as you want/need

If pressure is too low most engines will get "ticking" noises from valve train, under 4psi, which tends to go away at higher RPM/pressure, but a single lifter can fail so "ticking" is not oil pressure related


The 3.0l Vulcan did have issues with the Cam Synchronizer bushings, they would make a squealing noise after 80k miles or so
The Synchronizer is also the oil pump drive so.........................if you hear that noise change it out, as soon as practical

 

Thanks for the info. I'm going to setup the real pressure gauge and not worry too much about it. I did pick up a new ford pressure switch I'll swap out as well since it's already removed to get the test gauge. I might proactively change the cam synchronizer as I don't think it's ever been swapped and I'm at 196K. Seems like one of those engine killers that I've gotten away with.

I'm curious what you think about using a 12" x 1/4NPT hose to the block oil pressure port and then to a brass tee to fit both the factory switch plus an actual transducer for a gauge. Seems simple enough, but not sure if there's something I'm missing or not. I'd probably mount it on the firewall or somewhere out of the way there I think?

Thanks again,

 

Yes, you can "T" oil pressure port so you can have a stock switch and PS60 pressure unit, won't hurt anything

But BOTH are usually single wire Senders, so they use their threads as the ground, so if you add sealant/tape to the parts leave a few lower threads as bare metal so the engine ground can be passed thru each fitting

You can get off the shelf splitters, Google: oil pressure sender splitter images

Although the 3.0l's port being behind the head makes it a bit of a pain to split, or even get at, lol
What I might do because if its "pointed up" location is to install splitter but leave the higher sender off, and put a rag down around the new fitting
Disable spark(unplug coil pack)
Then bump the engine a few times using start motor so oil pushes any air up and out, then install final sender

 

Yeah, 'bit of a pain" is an understatement. Fun part was when the heater hose line broke at the plastic tee and sprayed me down with 190f coolant trying to get to it. Now I'm waiting for new hoses so that's fun.

And thank you again for the note on the ground for the switch. I would have completely forgot about that as I'm planning on moving it using a hydraulic hose. I don't think there's room down there to use the splitter directly so was just going to use a small extension. I'll have to ground the fitting some other way if I can't get it directly in.
These are what I picked up to see what I can rig.


Thanks again!

 

I can assure you that 11 PSI is fine. My 3.0 is at 220k and runs the same PSI at idle, and has been that way since I put the Glowshift gauges on around 180k.

Just a side note, if you choose to replace the switch, don't bother with the junk from the auto parts store. Motorcrafts aren't that expensive, and they last much longer than the aftermarket junk. I've owned the truck for 13 years and have tried both, Motorcraft's switch lasts 6-7 years and the aftermarkets don't make it past a week.

 

Yeah, I got a Motorcraft switch from the dealer for $32 in stock. Always OEM sensors if available. Not immune from early deaths, but a lot better odds than the other junk it seems.

Thanks

 

I've replaced a whopping total of 6, leaking oil pressure sending units.
In every case, the replacement worked fine. The last one was 15 years ago in the family Saab.
It's stunning that parts are so, so lousy now.