318 low oil pressure

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Joe1972dart

Joe1972dart

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Hello folks, I have a 1972 Dodge Dart with a 318 that I have owned for 2 years, it has 13,000 actual miles with no engine modifications. While driving it this weekend on the highway the oil light came on, I pulled over and checked the oil, it was a quart low. I added a quart and the light remained on. When started the lifters now tick, if I increase the rpms the ticking stops and light goes out, when it returns to idle the light comes back on. When I remove the oil fill cap with the car running and increase rpms I can see oil reaching the rocker arms. The things I have done or checked so far are

1. Changed oil and filter
2. Removed and cleaned oil pressure sensor
3. Hooked up mechanical gauge to oil pressure sensors port, at idle (750 rpm) it was 5 psi, at 1000 rpm pressure was 10 psi

Any further help or suggestions would be appreciated
 
if it only has 13000 miles on it in 47 years my money is on the bearings being shot from the acids in the oil that probably sat in it for years at a time just eating away at them
 
What weight and brand of oil are you using OP?

Did you read pressure at higher RPM's, say 2000 or 3000?

Have you pulled off a valve cover to see how much sludge is in there? Such limited amount of driving may have been lots of short trips that will build up moisture and crud in the oil and in the whole engine.
 
I wouldn't be running it too much more. Bearings can't be getting a hell of a lot of oil. I'd start by pulling the pan and the oil pump. New pump and gasket for less than $100 and hopefully you'll be good to go. If not the whole thing probably needs to come out
 
gzig5 said:
I wouldn't be running it too much more. Bearings can't be getting a hell of a lot of oil. I'd start by pulling the pan and the oil pump. New pump and gasket for less than $100 and hopefully you'll be good to go. If not the whole thing probably needs to come out
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I'd pull it and give it new bearings ,an oil pump , freeze out plugs ,and gaskets with a new rear main seal .At this point it's just parts replacement not engine rebuilding Replacing will cost a few hundred rebuilding will cost a couple thousand or more.
 
Thank you guys for your input and advice, I will test the oil pressure at higher rpms and will be replacing the oil pump. I will get back to you with updates. If anyone can think of anything else it would be appreciated.
 
How can you be sure the miles are correct?
What was the oil pressure a month ago?
 
I had a car once that had 50,000 on it and it was 40 years old.It had the same sort of problem and when I pulled the pan off there was 3 inches of this pudding in the pan covering the pick up. It was caused by lack of regular oil changes due to lack of use like your car .I pulled the motor and then pulled off the bearing caps one at a time until I got about a third of the way back . on the number 3 cylinder I found a spun bearing and when it spun it damaged the crank so the crank had to come out .After removing the crank I discovered that that spun bearing damaged the bore in the block where the bearing sits so in order to reuse this block I would have to align bore the damn thing. I junked the motor and used something else. What I'm saying is that if you plan on using this motor in this car you had better error on the side of caution or it can get very expensive. It's losing pressure for a reason and if the pump is making pressure at rpm chances are that the oil is bleeding out of a shot or marginal bearing either in the cam area or elsewhere.If it's not making any kind of knocking sound ,even ever so slightly then it's probably on the cam bearings.There could be cavities in the bearing material causing the oil to bleed . You need to open it up and find the cause or it will let you down in the near future.
 
I’m running Mobil 10w30, i do not know what the oil pressure was a month ago, as it has been running fine for 2 years. As far as the mileage is concerned I bought the car from my neighbor who has owned it since it was new, he said that he had the oil changed once a year.

Once again thank you all. If anyone else can think of anything please let me know. I will keep you updated, but will not be able to start tearing it apart until next week sometime.
 
Running that engine at higher rpm with that low of oil pressure is only going to hurt more parts. It doesn't matter what the pressure is at 4k rpm if it's 5psi at idle. It's too low to be running the motor. Change the pump and see where it is after that to see if you need to go deeper into the motor. Make sure the pickup is positioned correctly and clean.
 
gzig5 said:
Running that engine at higher rpm with that low of oil pressure is only going to hurt more parts. It doesn't matter what the pressure is at 4k rpm if it's 5psi at idle. It's too low to be running the motor. Change the pump and see where it is after that to see if you need to go deeper into the motor. Make sure the pickup is positioned correctly and clean.
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If I may repsectfully disagree.... The sensor is set around 8 psi.... 5 psi at idle is not all that different from 10 psi at idle, where the light would be off. The OP says it is 10 psi at 1000 RPM and will normally be higher and higher at high RPM's, and if sitting in the drive while revving up a bit with no load on the engine, and no rods knocking, then it is 99.99% unlikely to damage anything. That is part of why to check at 2000 and 3000.... if the pressure levels off, then it is likely a blockage, or the pressure relief valve stuck.

OP, be aware that Mobil 1 will be much thinner at low temps than non-synthetic oils. The cold viscosity rating is taken at about 105F test temps so cannot be used as an indication of how thick the oil is cold. Bottom line is that Mobil 1 is going to be thinner at all temps except really hot, thus will flow through the bearings at a higher rate, and that will result in lower 'line' pressures. Mobil 1 also tends to leak out of lifters more easily.

It is an excellent lube for bearings and having lost all oil pressure in prolonged racing events and not having bearing damage, I can attest that it will do a fine job of protection. But it WILL result in lower pressures than non-synthetics. Just be aware of this as you proceed.

And as for the oil changes, we still don't know the internal condition as for sludge and so forth.
 
If you say so. Gives me the willies to think about revving the motor with known low oil pressure. The oil film in the bearings is stressed more and there isn't enough pressure to properly maintain it. Not worth the risk in my opinion, but it ain't my engine so carry on.
 
Alright folks time for the update, I changed the oil to 10w40 and put on a new filter, started the car and I was shocked at the results. Now at idle 750rpm the pressure is 50psi, 1000rpm is 51psi, 2000rpm is 59psi, and 2500rpm is 62psi.
I appreciate everyone’s suggestions on what the problem would be, I still am going to pull the pan to see if there is a blockage, I am also going to check the top of the engine because I need valve cover gaskets anyway.
Again thank you I appreciate the help.
 
Wow... that IS quite a change! Much more than I would expect with just a change from 10W30 Mobil1 to 10W40 non-synthetic. Could be the pressure relief valve was stuck open in the oil pump....or the pickup was blocked.

What filter was on there before, and what is on now? What is the new oil? Were there any 'thickish' lumps that came out in the last oil change, and was the oil blackened or pretty clear?

Pulling the valve covers first will tell a lot about any sludging. Post up a pix or 2 of what you find under there.
 
My money would be on some kind of restriction that you obviously changed somehow when you did the oil change. 13K miles is all it has? That means it has sat a LOT. When that happens, moisture and nasties accumulate in the oil and turn it to sludge. I would be willing to bet it had sludge that had formed on the oil pump pickup and when you changed the oil, it loosened up and fell off in the pan. It probably got heated up and dissolved in the oil. My car did something similar after being run for about a week with a quart of Marvel's Mystery oil added to the oil. The change from 10/30 to 10/40 is not responsible for that much change in oil pressure. Ain't happenin. Something else is in play.
 
The original oil that was changed in favor of Mobil 10w40 was Mobil non synthetic 10w30, the first filter that was on there before the 10w40 change was a parts master filter, now has a motorcraft filter. No dark oil(clear), clumps, or even thick spots. And the milage is 13,000 miles(not a typo), I bought it from my neighbor who was the original owner who verified the mileage and I know the mechanic who worked on it before I got it and he also verified the milage. As for pulling the pan and covers, I will post pics of when I get around to doing it.
Again thank you guys for the help.
 
I don't know I would go to the trouble of pulling the pan just "YET". If you've verified the oil pressure is good with a known good mechanical gauge, I would drive it some. It might be ok.
 
Sorry..... I missed that it was not Mobile 1 but just Mobil.

To relate what others have found in the past and reported: When you get the valve covers off.... peer in between the coils of the intake valve springs and look to see if the umbrella valve seals are still there. They might now all be hardened and broken out and in the pan, blocking you pickup screen. After 47 years... good chance that they are gone, unless they got changed out.

Where does a "PartsMaster" oil filter come from? Sounds cheap....
 
They are made by Wix (“cheaper” model), I had one that I got from a service station I worked at.
 
I think you may have just learned a lesson on cheap filters.
 
Joe1972dart said:
They are made by Wix (“cheaper” model), I had one that I got from a service station I worked at.
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Then it's probably the same as O'Reilly Microguard filters. They are also made by WIX. I will have been with O'Reilly four years in May and have yet to see a bad Microguard filter. Not saying there aren't any. There are defective parts in all brands, but as of yet, I have not seen one in Microguard. If all these cheaper filters were so "bad" you'd see it all over the internet. I have seen a lot of bad stories regarding Fram. Never had a bad experience with Fram because I don't use them.
 
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