High oil pressure concern

[NashBronco]

I just changed the oil in my bronco today and now i notice that my stock pressure gauge is pegged at 80. I was running 10W30 Royal. I have read that several people are running the heavier 15W40 Rotella so i switched to that. no real reason for the switch. Now my gauge is pegged at 80 at idle. I was thinking that it may be the sending unit so i unplugged it and it dropped to 0 so i think that the sending unit is good ( i thought that i read that test somewhere on here). I also changed the oil filter. went from a Fram to a motorcraft if that matters.

anyway, Should i switch back to a thinner oil? Will it harm to keep the 15W40 in there?

 

[DirtDonk]

No, a 15w/40 will not harm your engine under normal circumstances. But something ain't quite normal here either. What did it read before?

More psi is good up to a point, but "more" is typically about 70psi cold, and 40-45psi warm.
Mine ran right in that range it's whole long life with 20w/50 oil. No spikes.
Yes, it's possible something is wrong with the filter, but I've never heard of oil being mis-labeled such that you might have received straight 40 weight for example. Could be possible, but I've never heard of it happening.
On the other hand I've heard of plenty of modern Chinese sourced products failing. Oil filters among them. But for most people that's usually the Fram that does it and they fix it with the Motorcraft!

Anyway, with luck someone knows what's going on. But did you let it warm up and did you see it go down at all?

Paul

 

[DirtDonk]

In addition, if it's truly at 80psi you're likely not in danger of damaging something like a filter housing. It's certainly not going to physically damage internal engine parts by having "too much" oil pressure, "but" it's possible to put too much pressure on the distributor drive gear and shear the pin.
So in a way, it can damage things.

But again, that level is not usually equated with shearing pins in older US made distributors. Modern Chinese ones may be different.
And pins shear even with normal pressures now and then. Thankfully it's a relatively rare occurrence though.

My brother's '66 Vette with 327 and mechanical oil pressure gauge would run up to 100psi upon cold startup, then run at 70 to 80 all day long, with it dropping into the 20's at idle.

Paul

 

[rmk57]

I'd change the oil filter first, could be the bypass in the filter is stuck closed.

 

[NashBronco]

Thanks Paul. It was running 40-50 before the oil change today. i let it run for 10 minutes and it staying pegged. i did not drive it around any.

 

[DirtDonk]

Cheap to test by changing the filter. Even if a bit messy!

Because a sending unit can fail in different ways, I don't think merely taking the wire off it will tell you enough to judge by.
Sure, it tells you the wire is fine, but does not tell you that the sending unit is not giving out a false reading.
For that you need an ohm-meter. And a temp gun would be helpful too.

Paul
Paul

 

[Joe473]

Why run the 15w 40? It's too heavy for normal use. If you are worried about flat tappet cam wear get high zinc oil or additive. Heavy oil may not circulate as well cold and may not lubricate as well cold. Also the higher pressure may also mean less flow and less cooling. If you dont have threaded oil gally plugs they could be in danger of blowing out and yes the dizzy shear pin on a cold morning as well. My theory is run the oil that the bearing clearances and piston clearances were designed for. 10 or even 5 w 30 should be great for recent rebuild with no issues. If you use your bronco in cold weather with cold starts the 15 may be too heavy.

Watch bargain oil filters. I had a "Free" stp oil filter on mine once. Autozone deal. Drove me nuts as oil pressure would decline in highway slowly running above 3000 rpm. Changed back to a motorcraft and all good.

I just changed the oil in my bronco today and now i notice that my stock pressure gauge is pegged at 80. I was running 10W30 Royal. I have read that several people are running the heavier 15W40 Rotella so i switched to that. no real reason for the switch. Now my gauge is pegged at 80 at idle. I was thinking that it may be the sending unit so i unplugged it and it dropped to 0 so i think that the sending unit is good ( i thought that i read that test somewhere on here). I also changed the oil filter. went from a Fram to a motorcraft if that matters.

anyway, Should i switch back to a thinner oil? Will it harm to keep the 15W40 in there?

Sent from my SM-G960U using Tapatalk

 

[68ford]

Physically impossibly going from 10-30 to 15-40 could double your oil pressure especially 40 to 80 or more at idle.

Nothing wrong with running 15-40. Literally millions of people run 15-40 Chevron delo diesel oil in flat tappet gas engines because they have additives in it to more than make up for lack of zinc these days.

 

[DirtDonk]

Agree nothing wrong with thicker oil (to a point of course) depending on your climate. Here in CA we've run 20w/50 in everything we had for well over 40 years with no obvious ill effects including fuel economy in some engines.
Old habits from motorcycle and other air-cooled days perhaps. Not to mention the great price on cases of Castrol GTX 20w/50 at Kragen every couple of months!
Multiple hundreds of thousands of miles in multiple vehicles with nothing but good luck.

Sure, 10w/40 is more recommended and maybe even more desirable for most conditions. But going up 5 points on the "winter" scale to 15 is not the end of the world. Even straight 30weight was run in these things, and the multi-vis oils are much thinner when cold than that stuff ever was.

So while I don't disagree with your recommendation Joe, I do disagree with the dire warnings against it. If I could run 20w in a 302 most of it's life and have normal performance all year round, and run the expected-range pressures as specified by Ford, a 15w is not going to do any damage due to it's viscosity unless it's somehow defective. Or in the coldest areas too of course. But it sounds like you may have had some personal experiences to the contrary, so that does count of course. Just that mine have been positive ones.

Not sure how cold it gets in Jackson, but right now, and especially in the summer I'm sure it's plenty warm enough for engines to thrive with a 15w/40 oil.

Paul

 

[DirtDonk]

Forgot to add, one way to find out! If changing the filter does not bring it back down, you could put in different oil and see what happens.

But I'd check the sending unit first. Are the other two sending unit gauges reading high too by any chance Nash?

Paul

 

[NashBronco]

Can I drive 5 miles with oil pressure at 80? Car show tomorrow morning!!

 

[68ford]

Almost positive the oil pressure sending unit is directly in main oil rail after the filter. Unless it's the other way, there is no way an oil filter could increase pressure down stream from itself.

 

[68ford]

Can I drive 5 miles with oil pressure at 80? Car show tomorrow morning!!

Yeas because it's still at 45psi

 

[blubuckaroo]

I thought mine had high oil pressure for years. Then I found I had a defective sender unit.

 

[68ford]

I thought mine had high oil pressure for years. Then I found I had a defective sender unit.

Kinda like the stories you hear about how people thought they were getting world record gas mileage that one time until the engine shut off showing 3/4 tank hahaha

 

[Broncobowsher]

drive it. So far you have not gotten the oil hot enough with the few minutes of idling for it to thin out. The 5 miles probably won't do it either. Takes me about 10 miles to get my oil warmed up.

Once had a car that we needed the oil fully warmed up but could only idle it. Took 2-3 hours of idling to get the oil warmed up. Oil is much slower than water in warming up.

 

[Joe473]

I didnt think I sounded that dire. I should have looked at location. Yes not getting that cold there or in Cali. Yes Paul years ago 20w50 was a common thing in old engines. Many times to counteract loose bearings to bring pressure up and consumption issues. Straight 30 was common but today most only to use it during break in. Some believed heavier oil was better. In some cases it may be. At this point I would never do it in the winter in Jersey. Ever try and start an engine with 20w50 in 20 degree weather? I believe if the engine is healthy the lighter oil flows better and lubes better at start up especially on cold mornings. I'm also running a roller cam. So less concerns here. For flat tappet I would look for additives and not viscosity. Never been a believer in heavier engine oils. My old Chevy and old 300 six I ran 10 30 in for many years and over 250k and both those engines never had anything more than plugs, water pump, and valve cover gaskets. Neither burned oil or ever had a lifter tap.

I have seen stock oil galley plugs blow out. Never on one of mine but years ago on a rebuilt engine running a high volume pump. Thicker oil, cold weather, high volume pump in tight engine could do it. Same for the dizzy shear pin.

Agree nothing wrong with thicker oil (to a point of course) depending on your climate. Here in CA we've run 20w/50 in everything we had for well over 40 years with no obvious ill effects including fuel economy in some engines.
Old habits from motorcycle and other air-cooled days perhaps. Not to mention the great price on cases of Castrol GTX 20w/50 at Kragen every couple of months!
Multiple hundreds of thousands of miles in multiple vehicles with nothing but good luck.

Sure, 10w/40 is more recommended and maybe even more desirable for most conditions. But going up 5 points on the "winter" scale to 15 is not the end of the world. Even straight 30weight was run in these things, and the multi-vis oils are much thinner when cold than that stuff ever was.

So while I don't disagree with your recommendation Joe, I do disagree with the dire warnings against it. If I could run 20w in a 302 most of it's life and have normal performance all year round, and run the expected-range pressures as specified by Ford, a 15w is not going to do any damage due to it's viscosity unless it's somehow defective. Or in the coldest areas too of course. But it sounds like you may have had some personal experiences to the contrary, so that does count of course. Just that mine have been positive ones.

Not sure how cold it gets in Jackson, but right now, and especially in the summer I'm sure it's plenty warm enough for engines to thrive with a 15w/40 oil.

Paul

Sent from my SM-G960U using Tapatalk

 

[Muddy1966Bronco]

Isn’t there an ohm reading you can do on the sending unit to see if it is defective? I’ve never seen oil jump pressure like that with an oil change, even jumping from 10w-30 to 20w-50. But I have personally had an engine drop to zero pressure after an oil change. Started out the driveway, tapped then gauge in concern, then engine locked solid. Clean engine, everything done correctly, never figured out what happened. So my guess would be something is blocking the sending unit, moved about by the oil change and filter change...and maybe even brought in by the new filter and oil. Or the sending unit just went bed.

 

[spap]

Interesting that people I have known and myself have seen lower oil pressures with royal pupal that why I stopped running it

 

[DirtDonk]

What were your numbers?
I think a lot of people have seen higher numbers with thick oil and lower numbers with thinner. Some members have been concerned about low pressure (maybe you posted up about that in the past?) but this is the first I remember where it's gone above and beyond normal from using what is still kind of a normal oil.
Then again, did someone comment that this is a new engine? Maybe the tolerances make a bigger difference here then.

More pressure could be expected from 20w/50 for sure. And maybe even by going from just 10 to 15 like the OP did. Just not double the pressure, from 40-ish to 80, with the same oil many here are using without seeing that extreme.

But he did say in the first post that his 10w oil was Royal Purple too. Maybe his previous readings were falsely low? And maybe his current reading of 80 is what he would have had with another brand of 10w oil.
Guess the only way to know anything for sure is to first verify pressure, then try different oils and filters to see how things change.

Paul