66 300 I6 high oil pressure

[jfm]

My slick is as follows:
1966 F100 long bed
1977 300 I6 engine
3 speed on the column
2.75 rear end

The truck is not run much, and the oil had been in it a while. The oil pressure had always registered high - in the 60 range. Changed the oil and filter last week, and now the pressure pegs the meter - 80 or so. Installed a new filter in case the first one had been clogged, but that didn't help. Truck cranks and runs fine. It ran hot a few days after the oil change, but that may have been just a coincidence. As I recall, it ran a bit hot once last summer. I removed the thermostat this time in case that may have been the problem there, but I'm afraid to drive it much to test it due to the pressure situation.

Any thoughts or suggestions would be appreciated.

[Hunter's 64]

not sure on the oil pressure , but removing the thermostat will not make the truck run cooler , it might for a few miles but as soon as the water reaches boiling temp,it won't cool it back down


Danny

[jkimbrel65]

Did you change grades of oil? Changed my from 10/40 to 20/50 Gained 12psi

Mike

[Toyz]

Let's hit the basics first:
What weight oil are you using?
What brand and model oil filter are you using?
Do any of your other gauges seem to be reading high (if oem gauges)?
Have you changed senders? We have found big differences even between oem senders.
What is the readings engine cold versus warmed engine?
The first step in diagnosis should be to verify the readings with a quality gauge. Any quality brand auto parts gauge kit could be used; a fuel injection test gauge could also be adapted to temporary diagnostic use. Verification of the pressure readings will narrow down the next steps. A normal gauge reading would indicate a problem with gauge, sender (see above) or wiring. If your other factory gauges (fuel, temp) are also reading high, it is likely to be the dash gauge voltage regulator, a common problem.
If the pressure is verified to be high, here's the next order of diagnostics:
If, as Mike posted, you have a heavy oil, you may simply need a lighter oil and a quality filter with a relief valve which does not allow un-filtered oil into the engine, ie, Motorcraft FL-1 This is very important at this point because, if your gauge is correct, the relief valve is probably working constantly. If your filter simply allows the oil to bypass the filter, that's not good! A poor filter could also collapse the element or bulge (or split) under the pressures you are indicating. Even a Mobil One filter has been reported to leak, so extreme oil pressure needs to be avoided.
If the correct oil and filter do not resolve the pressure, next is the oil pump. The oil filter relief valve may not be able to totally control pressures if the oil pump pressure relief valve is not functioning. The logical answer here is a new oil pump; cleaning might solve the problem for the time being; I would replace the pump to limit potential future problems.
Internal bearing problems could also cause the high oil pressure; I do not consider this likely since the pump relief would control the resulting high pressure, and other symptoms would probably be evident.
Here's hoping the problem is the sender, or the i.p.voltage regulator.
If it is the sender, more research is required to obtain a correct replacement, since Ford chose to use a poor substitute for a actual sensor. This,. and solutions is widely documented on the internet.
Hope this helps; sorry for the long-winded reply!
Paul

[ICEMAN6166]

very first i would check the wire to the sender, if its bare anywhere and contacts the block or other metal it will ground and peg the gauge at high.

[Limestone66]

Are those 'constant' readings yer talking about? 80 psi would be kinda high if it was constant, hot or cold. The pressure on my 352 is monitored by an Auto Meter oil pressure gauge and it does about 70 psi cold, then tapers down to about 50 psi at about the same mph after a few miles, and about 25 psi at hot idle. I run straight 40 weight with a Fram filter. Paul {Toyz} just about covered it as far as a preliminary breakdown of possible causes. Just tryin to help.

[Toyz]

very first i would check the wire to the sender, if its bare anywhere and contacts the block or other metal it will ground and peg the gauge at high.

Good point; that's an easy one I missed! Turn the switch on without starting engine; if the gauge climbs, then you've got an electrical problem in the wire, sender, regulator, or gauge; basically in that order of most common. The factory manual recommends testing the gauge with a 3 volt battery source, which should result in a "high" reading with a good gauge.
Ron, I suspect you are bumping the relief on that Fram filter when cold. That says a lot about the integrity of your engine!
I don't know what Fram filter you are using, but you might want to research a little on the various types, especially on a Ford.
Fram has many different filters; some will readily allow the un-filtered oil into the engine. Not trying to influence a choice you are happy with, but the filter design is a concern when you are approaching the limits of the pressure relief setting. They are supposed to relieve on differential pressure, but some will hit that differential on cold start.
Paul

[jfm]

Thanks, guys. I'll check some things and get back.

[Limestone66]

Good luck with that 'jfn'. Could very likely be just an electrical problem giving you the higher readings.

No Paul, just thru it on there as they didnt seem to have Motorcraft in stock at the time. What do you mean, bumping the relief? With all due respect and without hijacking this post. Just curious.

[BarnieTrk]

I run straight 40 weight with a Fram filter.

Ron,
Why straight 40 wt oil?
Seems kinda heavy to me, even for Florida use...... I'd use a good, a quality-grade 15W-40 diesel oil in any 60s-70s vintage engine driven on the street. I suggest diesel oil because it has a good amount of zinc in it which this old engines prefer. One brand that fits this description is Chevron DELO 400 Multi-grade 15W-40.

The oil pressure had always registered high - in the 60 range. Changed the oil and filter last week, and now the pressure pegs the meter - 80 or so.

jfm,
Does the oil pressure gage stay pegged ALL THE TIME - or only for the first 5-10 minutes of running? As Mike indicated earlier, if you're using a heavy wt oil, it would likely peg your gage until things get warmed up...then the pressure would be expected to come down some.

BarnieTrk

[Toyz]

I agree with the lighter diesel rated oils comments. A little searching on line will reveal concerns with Ford's pressure sensors; thus I would agree it may be an electrical based problem possibly combined with a thicker oil. I would expect the pump relief valve to maintain a lower actual max pressure, hence the concern about bumping the relief valve with a thicker oil.
Ron, the expressed concerns with some Fram filters is the differential relief valve material and location; allowing dirty bypassed oil past the filter, plus supposed leakage past the valve seat. I do know that going to a Motorcraft or the pricey Mobil One filter will often solve "rattling" problems on startup.
Paul

[Blackwaterforge]

I run Delo 15-40 in my truck.
The engine is a 75 300 6 cylinder.
Oil pressure is 80 psi cold.
Needle stays between 80-90 (Bronco gauge) at 2500-3000 rpm
Hot idle around 30 lbs.
Oil pressure has been consistent for three years 75000 miles.
It is the same with mechanical gauge.

[Toyz]

Those high pressures put added importance on a quality filter as well as a stronger than stock pump drive shaft!
Paul

[jfm]

My son cranked the truck this morning, and he said that both the oil pressure and temp gauges immediately pegged high, so it may be the dash voltage regulator. Where is that, and what does it look like?

[ICEMAN6166]

My son cranked the truck this morning, and he said that both the oil pressure and temp gauges immediately pegged high, so it may be the dash voltage regulator. Where is that, and what does it look like?

on the back of the instrument panel
the rectangular piece on the bottom with the 2 tabs




i use 15w40 in my y block. i have 60 psi at startup, about 55 at highway speed and 40 at warm idle.

[jfm]

Okay, got it. Thanks, iceman. Called AutoZone. $50+! LMC has it for $30 plus shipping. Any way to test it, or is there nothing to do but replace the little devil?

[Limestone66]

Glad you found the culprit 'jfn'. What this little devil does is kick down yer voltage to about 7 volts for the stock OEM factory gauges to work properly. I did a little bit of research on this little voltage regulator because when i first bought my slick, none of the factory gauges worked. A multitester told me right off what the problem was as i was getting a full 12 volts in but almost nothing out going to my gauges. Acquired a complete dash thru 'Evilbay' from a 66 donor and it came with the little voltage regulator already on it. This little jewel controls all of yer factory gauges just like mine, including the fuel level gauge. Replace that with a new one and i beleive strongly that yer high readings will be a thing of the past. Yer old VR on the back of yer dash aint dead yet but it wont be long before it does go out, rendering all of yer gauges useless and unresponsive

Barnietrk-I am always open to suggestions concerning ol 'Limestone'. You and 'Paul' and others, iceman too has helped me since the beginning with my old pickup and i value yer wisdom and sheer on hands experience very highly. Some of the old timers {older then me} suggested that i just run straight 40 weight because the old Fords just seem to run and live longer then going to something different, although synthetic oil has been tried and trued. My oil pressure seemed a little diffrent after the heads were rebuilt {ahhh, total bliss to have 8 cylinders firing again} 15 to 20 at hot idle using synthetic and 65 to 70 on cold startup. Not knocking it but hell man, i run 20/50 synthetic 'screaming eagle' oil in my O5 'Deluxe' and am happy with that, it be expensive as hell but it good oil for the newer bikes, but not for 'Limestone'. Oil viscosity will break down under high temperatures, especially living in Florida, so i thought a good standard grade of oil like straight 40 weight should do the trick over synthetic. Just 'MHO' for what its worth.

jfn-I humbly apologize for hijacking yer post, and to our 'MODS' for knowing better.

[Lowell]

I had to replace my vr , the gauges suddenly pegged out and burned out the temp gauge before i could disconnect them.
I got a regulator from Macs . I got a temp gauge from Slickmainer.

[jfm]

I had to replace my vr , the gauges suddenly pegged out and burned out the temp gauge before i could disconnect them.
I got a regulator from Macs . I got a temp gauge from Slickmainer.

Hope that didn't happen to me. Looks like the gauges were getting 10.5 volts. Maybe that won't be enough to kill 'em.

As to a replacement, I thought I would try this:

1968 FORD FAIRLANE INSTRUMENT CLUSTER VOLTAGE REGULATOR
http://www.youtube.com/watch?v=SzLifw0W94g

[BarnieTrk]

Oil viscosity will break down under high temperatures, especially living in Florida, so i thought a good standard grade of oil like straight 40 weight should do the trick over synthetic. Just 'MHO' for what its worth.

Ron,
I stick to my earlier recommendation of running a good, a quality-grade 15W-40 diesel oil, such as Chevron DELO 400 Multi-grade 15W-40. It has the extra zinc and I'm sure it will handle Florida's heat. Furthermore, I'd say if you change your motor oil & filter every 3K miles or every 6 months (whichever comes first), your 352 will stay happy and not have an oil-related problem. You may even consider adding some LUCAS HD oil stabilizer; http://www.lucasoil.com/products/displa ... 25&catid=2
My two ol' FE 390s appreciate it!




jfm,
I don't know if or how well that setup will work for ya......... Keep us posted on your progress!

BarnieTrk