Low oil pressure

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g49bridges

g49bridges

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Need some help...trying to figure out whats wrong. I recently bought a 340 and I've got low oil pressure. As I said, I bought this one, did not build it. The engine had been in a guys duster. He pulled the engine and sold the car, and was in the middle of putting it in a truck when he had to sell it due to divorce. So really I know very little about the details of the motors internals. Dropped it in my duster and when it starts cold the oil pressure was at about 50lbs, and then 25 when it warmed up. Now it's dropped to 40 cold, 18 when it warms up to 180. When you put it in gear it drops to 10 lbs, but comes back up to 40 lbs when its running at 2000 rpm. No noise in the top end at all. Also, when you fire it up the pressure comes up slowly rather than suddenly. I did have the pan off before dropping the motor in the car and everything was properly attached/tightened up. Didn't know if that's normal(ish) on these 340s, if its ok to run like that, or what. Anybody have some insight into this? Engine runs very strong and sounds great, so really not wanting to risk damaging the engine.
 
There's nothing wrong. That's normal oil pressure.
 
It probably has slightly large bearing clearances.
In my experience that is why the oil pressure rises slow.

Your engine would probably be just a bit faster than the next guy with all other things being equal. :D
 
Its a mechanical gauge. Not a high end gauge, but I swapped it out for another one I had in the shop and it read the same. So I'm guessing the gauge is right. Bearing clearances being a little loose is a possibility. Engine did see the track quiet a bit before I got it.
 
Have you done an oil change on it? Put fresh oil and a new high quality filter on it. This will also give you a chance to inspect the oil that comes out for any metal shavings. Make sure to use a clean drain pan.

But from what you describe, I don't think you will find anything out of the ordinary.
 
RustyRatRod said:
Have you done an oil change on it? Put fresh oil and a new high quality filter on it. This will also give you a chance to inspect the oil that comes out for any metal shavings. Make sure to use a clean drain pan.

But from what you describe, I don't think you will find anything out of the ordinary.
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Agreed. High Quality oil filter= no orange frams. Something like Wix/Purolator.

Actually have seen oil pressure rise just by removing a fram and installing something else.
 
Running royal purple 10w30 and a fram filter. Will be changing to a different brand filter on first oil change. Never knew how bad the frams were. Only recently started using the frams, but not too impressed with them.
 
g49bridges said:
Running royal purple 10w30 and a fram filter. Will be changing to a different brand filter on first oil change. Never knew how bad the frams were. Only recently started using the frams, but not too impressed with them.
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Everyone has their own opinons when it comes to Oil Filters. I have been running Fram oil filters for decades on all my High performance vehicles along with my every day runners and I have had not 1 problem and as for increasing your oil psi by removing your Fram Filter and going with some thing else, I just don't by that. May I ask why are you not impressed with Fram ? What dont you like about it?
 
Gator said:
Everyone has their own opinons when it comes to Oil Filters. I have been running Fram oil filters for decades on all my High performance vehicles along with my every day runners and I have had not 1 problem and as for increasing your oil psi by removing your Fram Filter and going with some thing else, I just don't by that. May I ask why are you not impressed with Fram ? What dont you like about it?
Click to expand...

http://www.minimopar.net/oilfilters/opinions.html

Filters To Avoid



Fram Extra Guard

Years ago Fram was a quality filter manufacturer. Now their standard filter (the radioactive-orange cans) is one of the worst out there. It features cardboard end caps for the filter element that are glued in place. The rubber anti-drainback valve seals against the cardboard and frequently leaks, causing dirty oil to drain back into the pan. The bypass valves are plastic and are sometimes not molded correctly, which allows them to leak all the time. The stamped-metal threaded end is weakly constructed and it has smaller and fewer oil inlet holes, which may restrict flow. I had one of these filters fail in my previous car. The filter element collapsed and bits of filter and glue were circulating through my system. The oil passage to the head became blocked and the head got so hot from oil starvation that it actually melted the vacuum lines connected to it as well as the wires near it.

Fram Double Guard

Another bad filter idea brought to you by your friends at Fram. The filter itself is a slightly improved design over the Fram Extra Guard, but still uses the same filter element. It has a silicone anti-drainback valve, a quality pressure relief valve, and enough inlet holes for good flow. The big problem is that they are trying to cash in on the Slick 50 craze. They impregnate the filter element with bits of Teflon like that found in Slick 50. As with Slick 50, Teflon is a solid and does not belong in an engine. It cannot get into the parts of the engine that oil can and therefore does nothing. Also, as the filter gets dirty, it ends up filtering the Teflon right out. DuPont (the manufacturer of Teflon) does not recommend Teflon for use in internal combustion engines. Please do not waste your money on this filter.

Fram High Mileage

Yet another bad filter idea brought to you by your friends at Fram! Gotta love these guys. It's a Fram Extra Guard with a weird goo cartridge suspended on the clean side of the filter, blocking the outlet. It's supposed to be some kind of additive package, but if you want a high mileage oil, buy a high mileage oil. I don't trust these guys...sorry.


When it comes apart inside and all of the cardboard clogs up your oiling system, you may reconsider.
 
What may be acceptable for Chrysler warranty specs is not always optimal. It is my humble opinion that 10 psi at idle is way too low. It is an indication that there is something seriously wrong or worn. Anything less than 20 psi on a fully warmed up engine idling in gear is cause for concern. Raise the rpm I would want to see a minimum of 50 psi. That would be my high mileage specs. Brand new engine with stock oil pump I expect around 45 at idle and 70 + at high rpm. This is my opinion though.
I once spun a bearing on a 340 and had oil pressure very similar to what you describe. Idling around 10 and maxing out at 40. No knocking sound.
 
Any reason to run 10w30? If you are doing it to save gas, dont. The 1/3 of a mpg is not worth wasted crank or thrown rod. use 20w50 like you should. Back in the day, before gas got stupidly expensive, 20w50 was the norm in V8 engines. 10w40 was for imports or wintertime in cold climates. The big car companys use super thin oil because that 1/2 mpg adds up over the entire fleet mileage. Thats what energy credits are for, your overall cooperate mileage figure. They do this to get better #'s so they can still sell hummers and expeditions without having to buy energy credits, like big chemical companys buy "clean energy credits" so they can pollute more with less harassment from EPA.

Notice how engines dont last as long anymore, ever wonder why? New engines are now using 0w10 and 0w15...total bullshit. They will tell you 10w40 will damage a new engine, how? Do they run less bearing clearance? No.

My advise as a 30 year mechanic, get a Wix or factory filter and run 20w50 and see if you get better pressure at idle. My guess is 20+ at idle and more at rpm. Shouldnt drop as much when hot either. If you dont beleive me, look in a factory service manual for your engine year, it will say 20w50 for temps above 40 deg. Surprised nobody mentioned this....
 
340dartley said:
What may be acceptable for Chrysler warranty specs is not always optimal. It is my humble opinion that 10 psi at idle is way too low. It is an indication that there is something seriously wrong or worn. Anything less than 20 psi on a fully warmed up engine idling in gear is cause for concern. Raise the rpm I would want to see a minimum of 50 psi. That would be my high mileage specs. Brand new engine with stock oil pump I expect around 45 at idle and 70 + at high rpm. This is my opinion though.
I once spun a bearing on a 340 and had oil pressure very similar to what you describe. Idling around 10 and maxing out at 40. No knocking sound.
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The factory oil light is cut on when pressure drops below 3 PSI. 10PSI at under 1000 RPM is plenty.

You have to remember what PSI stands for. Per square inch. So, that means for every square inch of oiling system, there is 10PSI lumbering along at 800 or so RPM. I am sure there is more than 5 square inches of oil galleries. Do the math.

While there may or may not be some bearing wear, the pressure is perfectly acceptable.
 
Says who? Show me where a factory Chrysler service manual says to run 20/50 in an engine. Never have and never will. Oil viscosity has little effect on oil pressure.

A good example would be some of these newer engines where manufacturers recommend 0w20. The reason for this is to get oil to the engine QUICK on startup. Once the oil reaches operating temperature, it changes to 20 weight viscosity. They bury the oil pressure gauge cold when the oil is 0 weight.

When you spout off an opinion, make sure you let everyone know that, because to my knowledge, Chrysler never recommended 20/50 for any of these older cars. Mostly straight 30 weight and 10w30 as multi viscosity oils came into vogue. I've rarely even seen straight 40 or 10w40 recommended.

You've been watching too many Castrol commercials.

And engines don't last long anymore? Puhhleeze. What planet are you living on? Pluto?

Newer engines are lasting longer than older ones ever did and it's due in part to newer oil technology. Fuel injection also plays a role. I have seen more newer engines than I ever did old ones with 200K plus miles on them.

You are just dead wrong.


magnummopar said:
Any reason to run 10w30? If you are doing it to save gas, dont. The 1/3 of a mpg is not worth wasted crank or thrown rod. use 20w50 like you should. Back in the day, before gas got stupidly expensive, 20w50 was the norm in V8 engines. 10w40 was for imports or wintertime in cold climates. The big car companys use super thin oil because that 1/2 mpg adds up over the entire fleet mileage. Thats what energy credits are for, your overall cooperate mileage figure. They do this to get better #'s so they can still sell hummers and expeditions without having to buy energy credits, like big chemical companys buy "clean energy credits" so they can pollute more with less harassment from EPA.

Notice how engines dont last as long anymore, ever wonder why? New engines are now using 0w10 and 0w15...total bullshit. They will tell you 10w40 will damage a new engine, how? Do they run less bearing clearance? No.

My advise as a 30 year mechanic, get a Wix or factory filter and run 20w50 and see if you get better pressure at idle. My guess is 20+ at idle and more at rpm. Shouldnt drop as much when hot either. If you dont beleive me, look in a factory service manual for your engine year, it will say 20w50 for temps above 40 deg. Surprised nobody mentioned this....
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Ruysty, most "dummy lights" are actually set for 5-7#. While 10 psi might sound like a lot, consider cylinder pressures and how that equates to pressure on rods and crank. The other thing to consider is that the oil sender is located directly above the main oil passage right off the pump. By the time your 10psi reaches the farthest front rod journal, how much pressure is lost? Now think about just what it takes to squirt that oil into a .002" gap between a spinning rod bearing. How does that 10 psi sound now, kind of low, right?

If you want an example, put a 50' garden hose on faucet, then crack the faucet 1/3 of the way...flow not too bad but now put another 50' hose on and see what the flow does, you will have to open faucet more to get same flow. Now step on hose...while a hose is not an engine, they both have to follow the laws of fluid dynamics, fluids all take the path of least resistance, like to pressure sender.

I would not run an engine on 10 psi at idle, unless it was a rental:D
 
RustyRatRod said:
Says who? Show me where a factory Chrysler service manual says to run 20/50 in an engine. Never have and never will. Oil viscosity has little effect on oil pressure.

A good example would be some of these newer engines where manufacturers recommend 0w20. The reason for this is to get oil to the engine QUICK on startup. Once the oil reaches operating temperature, it changes to 20 weight viscosity. They bury the oil pressure gauge cold when the oil is 0 weight.

When you spout off an opinion, make sure you let everyone know that, because to my knowledge, Chrysler never recommended 20/50 for any of these older cars. Mostly straight 30 weight and 10w30 as multi viscosity oils came into vogue. I've rarely even seen straight 40 or 10w40 recommended.

You've been watching too many Castrol commercials.

And engines don't last long anymore? Puhhleeze. What planet are you living on? Pluto?

Newer engines are lasting longer than older ones ever did and it's due in part to newer oil technology. Fuel injection also plays a role. I have seen more newer engines than I ever did old ones with 200K plus miles on them.

You are just dead wrong.
Click to expand...

So you are saying that Car company use 0w10 to make the engine last LONGER? Horseshit! Since when do big car company's give a damn about customers engine longevity ? They are driven by greed not building long lasting cars. In the 80's they introduced something called "planned obsolescence" When cars last over 100K miles, company's loose out on new car sales. In 70's Datsun, Toyota, Honda's would all go 200K + I dare you to try that with a Neon today, you would be lucky to make 100 without major issues. Or do they make the oil pan, intake manifold and valve cover out of plastic because it lasts longer than steel ones?

I have noticed many of your posts telling people they are wrong or they are uninformed, I on the other hand was offering my opinion to OP as a 30 year ASE Master Tech and engine builder. Not sure how many engines you have built or if you work in automotive field but telling someone they are dead wrong without any proof is pure crap.

You have scripture quoted on your profile, are you going to tell me I am dead wrong if I dont believe it? Do you have proof its true or are you just running your mouth with no proof?
 
Here is some math...oil in the engine does not lumber along at 800 rpm,if you measured the flow(speed) of oil "lumbering" through the galleries it would certainly NOT be measured in rpm, ft/sec would be a more common unit. If it was measured in rpm(its not),your math is still wrong, the oil pump is driven off the cam and last time I checked, the cam did not turn at the same speed as the crank where rpm is measured.

PSI doesnt stand for "per square inch" it is abbreviation for pounds per square inch.

There is no correlation between inches of oil galleries length and the amount of measurable pressure in said gallery with the exception of pressure drop due to length.
"I am sure there is more than 5 square inches of oil galleries."
I believe it would be "are more" but I am no English major...what does 5 square inches of oil passages have to do with pressure, are you saying 5" of passages has 10 psi in each square inch so that equals 50 psi? Or were you referring to there being 5 sq in of oil at 10 psi meaning there is plenty of oil at 10 psi?

My guess on 10 psi is the engine is either worn or improperly built/assembled thus meaning you risk blowing it by ignoring it. Remember,if its 10psi at gauge, one of the first passages from the pump exit, its not going to be that much in the passages in rod journals of the crank at front of the block. My opinion of course.



Pounds per square inch
From Wikipedia, the free encyclopedia

The pound per square inch or, more accurately, pound-force per square inch (abbreviations: psi, lbf/in2, lbf/in2, lbf/sq in, lbf/sq in) is a unit of pressure or of stress based on avoirdupois units. It is the pressure resulting from a force of one pound-force applied to an area of one square inch:
 

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20W-40 oil is the heaviest oil viscosity I have found yet in any Mopar FSM's of this era (but I don't have them all) and that is only for continuous temps above 32F . I would not be telling people to use 20W50 without knowing their climate and use patterns; Missouri gets waaay below freezing at times, and too heavy an oil will result in engine damage due to it not getting picked up and circulated properly at a cold start. This is even more likely to happen on an older engine that may have a worn oil pump. So, 20W-50 for the OP in this case would be a big mistake IMO. Maybe move up to 10W40, of a good grade oil.

My concern for the OP's case is that his pressure appears to have dropped as he is operating it. I would be thinking that the oil pump is well worn or the oil pressure relief valve in the pump is not closing right and allowing some pressure drop. It may also have the lighter pressure relief spring that limits pressure to 55 psi even with the pump rotors in perfect condition. I'd be replacing the oil pump as a precaution after seeing the cold and warm operating pressures drop across the broad.

BTW, I raced long distance races for years on Frams..... but am not sure I would use them now.
 
:happy1:

:happy1:not to get in the middle here, but doesn't that service manual pic you posted show an minimal (meaning the least that is still acceptable, correct?) curb idle oil pressure of 6 PSI?

now, I will agree that if you say 6PSI at 800 RMP is acceptable, and 30 PSI at 3000 RMP is minimal, then there is a slight increase required that equates to a little more then the 10 PSI per 1000 RPM I referred to earlier, but I think its a pretty decent "rule of thumb"
 
And from the looks of the manual citation above, 10 psi per 1000 RPM looks to be a minimum, not necessarily 'normal', and could be considered the low pressure service limit of the oil pump. The range cited is 30 to 80 psi at 3000 RPM, so 50 or 60 would be mid range, and that agrees spot on with the lower pressure relief springs put in the oil pumps (55 psi).

I have been trying to reconcile in my mind the old saw of '10 psi per 1000 RPM' with the new pump pressure levels in these engines; they don't seem to agree all that well for these engines. But, saying that 10 psi per 1000 RPM is a minimum acceptable level makes some sense, to me at least. And I would apply this specifically to these engines; other engines are different. The Chrysler engineers seemed to have designed these engines for higher than typical operating pressures.
 
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