Intermittent oil pressure fluctuation.

[FORDBOYpete]

We are talking about a 1995 4.0L V6 RWD Aerostar with 250K Miles on engine. Some days the oil pressure reads between the R and M in NOR|MAL and on other days it barely reaches the \NORMAL. It is niether a gauge, nor sender, nor wiring problem. It's a 30Lb pressure fluctuation intermittently out of Oil Pump. Bad or Worn Oil pump perhaps, or maybe dirty or restricted pick up screen or tube ?

So pump & pick up tube have been replaced with new OEM parts. Pan was down & beyond some varnishing from 250,000 miles was very clean. All was cleaned, new Pump & Pick up Tube/Screen installed. Engine was reassembled & ran fine for a few weeks, then LOW Oil Pressure again. It was only putting out 22-22.5 lbs @ 2500 Rpm Hot or Cold. For no apparent reason a few days later it puts out 52-55 psi @ 2500????

Temperature, Surface/Pitch, Angle nor anything else seem to cause pressure loss to occur. It's totally random & unpredictable or has been so far. Engine has never been overheated, nor run low on engine oil. No leaks or loss visible. Because of my humongus mileage I've run Castrol 20-50 GTX for last 45K-50K miles or 3+ years or so. Makes no difference if I "Hammer Down" on it or drive like "Granma" would, it seems to have a mind of it's own.:scratch:

Besides running Castrol GTX 20w-50 I only use Motorcraft Filters, I changed oil twice a year @ about 6,000 mi intervals, Oil & Filter every time by the book. I have a few more 4.0L Colognes, but really I'd like to know what's going on with 4.0L in my Aero now. .. . . . .

CIAO Y'all

FBp

 

[BrooklynBay]

What kind of test gauge did you use to take these pressure readings? Did you replace the sending unit?

 

[FORDBOYpete]

Hey Brooklyn Bay. . . How ya doin' ?
I've an old Stewart Warner mechanical, capillary, Gauge with a short (20" hard line) hose I can swap fittings on, left over from my racing days I use for testing Oil PSI etc. It's a 150# PSI unit from a Peterbilt I had. It is close enough for what I do. It's a deluxe mechanical capillary lighted gauge. I don't believe it's a sender problem. PSI actually drops off, like somebody shut off or restricts supply of oil.
The OEM Original pick up & screen was not clogged or didn't appear cracked or leaking, but since I already had an OEM replacement & was apart I put new stuff back in there anyway. It ran fine for several days then did it again. It's been intermittent ever since. But usually it corrects itself at some point.

Last week I had to take my son to MCO/Orlando to return to base in Vilseck Germany after his annual leave for a 13 month tour in Afgahnistan. It's 60-65 Mi trip, 1 way, my wifes Taurus had a CEL & 2 codes, P0403 & a #1 Cylinder Misfire. It was not up to the trip at all. I believe it's a degenrated plastic connector housing on #1 Injector. We've been having extreme heat & drought causing plastic connectors to fail in hot spots under a hood. Like Heat Indexes over +110*F. Matter of fact Ian said Kandahar hits +130F & isn't near as hot nor as stiffiling as Florida this year. . . .

Anyway, I cranked it up when it was time to go. I got a 22+ PSI read. U.S. Military doesn't wait or buy Hoakey excuses so we made the trip. I never got over 22-22.5 PSI. When I got home I had noisy wrist pins, so I know I ran lo PSI & I hurt a really good 4.0L. It wasn't gauge or sender issues, Brooklyn. It was a lack of PSI.

Saturday We pulled a Radial 14 cylinder Aircraft Engine off an engine stand & took it to Museum Site to hang on a WW II Warbird we're restoring. I used my Van. It started with 55 PSI & ran all day, well half a day & kept 55 PSI whole time. Last nite My wife, upper eschelon personnel in our state Div or Forestry had to go to a "compound" to get her state vehicle for fire related business, again my Aero ran 55 psi @ speed & nary a sound from her wrist pins. . . .

If you want a peek at the War Bird go to DeLand Naval Air Station Museum on facebook, the whole story is there. . . . So's a pic of my 95 XLTN with the trailer & Load on it. Check it out.

CIAO

FBp

 

[BrooklynBay]

Just as an experiment, run some Seafoam in the engine oil for about an hour, then drain the oil while it's still warm, use Mobil 1 0-30 or 0-40 synthetic oil, and test the PSI. I'm sure that it might solve the problem.

 

[FORDBOYpete]

Out of curiosity, what do you think my problem is that Seafoam could cure?
I mean what in a pressurized system would respond to Seafoam? Or what can be in it that would stick ? Everything with valves and pressure control is rather new. Internal engine is really pretty clean. I mean I've been running GTX Wakefield grade engine oil which is petroleum based, not Synthetic. Unlike Pensylvania grade or "mixed batch" grade engine oils Wakefield contains no contaminents like parrafins or potash etc. I Lacked many visible deposits when I had pan off. Usually an engine with 250K has something built up but that 4.0L was particularily clean, except for baked on varnish in pan. No sludge or pan accumulation to speak of when torn down to install the pump & pick up tube/screen a couple months ago.
Also Parillo changed to another brand of Synthetic Oil other than Mobil 1 & it was great until his timing cover, rear main & o-ring type valve seals began to leak engine oil both internally and externally at main crankshaft seals. The fine print did explain that problem might occur in vehicles with big Mileage on them. Not sure what Parillo's Mileage could have been, but my mileage = 250K
and in my book that's a lot of miles for a car on road like mine has been the last few years.

CIAO

Pete @ FL

 

[BrooklynBay]

My 88 van had oil pressure issues when I first got it (4 years old with less than 80K miles). I replaced the oil pump, and it didn't make any difference. I ended up replacing the pump again, and it still didn't make a difference. I didn't know about Seafoam back then, so I kept using motor flush along with Mobil 1 0-30. I even modified the sending unit because it kept going bad (with a 1/4" brass boiler trap). The motor made more noise with such a fine grade oil, but it eventually started to show normal oil pressure. I didn't have to replace the pump or the sending unit either. Small passageways within the engine could clog over time.

 

[FORDBOYpete]

Okay maybe I'll give it a try this week. I ran Seafoam thru intake before with a '93 4.0 V6 on "G-P". I didn't notice any dramatic difference, except it didn't smell too good as I ran it out of the system by driving it. I had an exhaust code for a few times until I got whole can thru' the system & it eventually ran clean again. I can't say there was a dramatic appreciation in performance though. But It was a hoot driving past the "Law" as if we were supposed to be driving past them.
CIAO
FBp @ FL

 

[BrooklynBay]

You could use motor flush or a quart of transmission fluid if you don't want to use Seafoam.