Intermittent oil pressure/lack of oil pressure

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buffoni88

buffoni88

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So, got my intake on with no vacuum leaks, FINALLY. Now, here's my problem. Yesterday, I flushed out my heater core, got the heat back again. I was about to go inside, when I noticed I had about 5 psi oil pressure. HUH? Thermostat was at 195. Just went out this morning, started it up, and had about 60 psi oil pressure, didn't let it warm up to 195 again though, it's too cold out right now and didn't want to stay out there. What would be the first thing I should check? I have an aftermarket gauge, so I know it's not the pressure sender. Any ideas? Should I check the pump/screen?
 
Or start with the oil filter? I did an oil/filter change after I put it the intake on. I'm running full synthetic 10w30. I know I probably left out some pertinent information, I tried not to though. This guy is still learning, so bare with me!
 
bearings & pick-up. Get the pan off and start checking the bottom end, and pump. If you don't disaster is only a short time away.
Al
 
Doing that definitely isn't a one day job, is it. I was just looking at pan removal in my service manual, and it's a lot more involved than I ever thought it would be. So what if I were to take off the filter, cut it open, see a bunch of crap in it, then put a new filter on. Do you think that'd be sufficient? Or would you recommend taking the pan off no mater what
 
mopar head said:
I lost pressure once with synthetics,
changed filter, went back to dino oil, got it back!!
Try that first...
Click to expand...

Hm...I'll definitely try that first! What viscosity oil should I use? 74 318 with about 56k miles. I'm using the mopar filter, should I switch to a different one you think? I just cut the filter I had open, and it looked pretty clean.
 
mopar373 said:
bearings & pick-up. Get the pan off and start checking the bottom end, and pump. If you don't disaster is only a short time away.
Al
Click to expand...

Which bearings? If I were to take off the oil pan, they'd be there, right? The crank bearings? Can you change those without doing a rebuild, engine still in car?
 
You can change the bearings with the motor in the car, but it is a real pain.
I think time wise it would be quicker to pull the engine.

First I would try a different viscositys of oil to see if your pressure improves, I would start with about a 10w-40.
 
So when you say that synthetic will cause a pressure drop, what is happening internally that is blocking the pressure? Is it clogging the pickup, just not able to get through it with enough pressure?
 
buffoni88 said:
So when you say that synthetic will cause a pressure drop, what is happening internally that is blocking the pressure? Is it clogging the pickup, just not able to get through it with enough pressure?
Click to expand...
I`m not saying it does-just saying it happened to me.
maybe my engine is haunted, It did come from a wrecked 69 Cuda, dont know the story:snakeman:
 
Low oil pressure at idle with thin synthetic is not necessarily a problem.

At 200f, that oil is as thin as any clean 30 weight oil -synthetic or not. Some synthetics get to the proper viscosity quicker than conventional oils.

If you want more pressure at idle, go to a thicker oil like a 20-50. All that lower number means is how it behaves when cold. At operating temp, the higher number is the actual weight of the oil.

I have noticed the mopar crowd tends to panic and rip an engine apart at the slightest question. How about some more info first:

What is the hot oil pressure @ 1500 engine rpm in neutral?

What about 2500 rpm?

How long have you been running the synthetic? How many miles on the filter?

As long as the pressure comes up off idle, there may be nothing wrong. I have a fresh 392 in the yard that has maybe 2psi at idle hot. It has no problem hauling 19,000 pounds of truck around all day long, much of the time @ WOT. Lots of flow across those bearings keeping things cool.

B.
 
bohica2xo said:
Low oil pressure at idle with thin synthetic is not necessarily a problem.

At 200f, that oil is as thin as any clean 30 weight oil -synthetic or not. Some synthetics get to the proper viscosity quicker than conventional oils.

If you want more pressure at idle, go to a thicker oil like a 20-50. All that lower number means is how it behaves when cold. At operating temp, the higher number is the actual weight of the oil.

I have noticed the mopar crowd tends to panic and rip an engine apart at the slightest question. How about some more info first:

What is the hot oil pressure @ 1500 engine rpm in neutral?

What about 2500 rpm?

How long have you been running the synthetic? How many miles on the filter?

As long as the pressure comes up off idle, there may be nothing wrong. I have a fresh 392 in the yard that has maybe 2psi at idle hot. It has no problem hauling 19,000 pounds of truck around all day long, much of the time @ WOT. Lots of flow across those bearings keeping things cool.

B.
Click to expand...


Yes, I may be over-reacting, I just wanted some opinions though. I've already got the oil drained, so I couldn't tell you what the pressure is at 2500 rpm. I've been running synthetic for a couple months now, but just noticed it happening. I did just get done installing the intake though, and I did drill out the heads to install heli-coils. I may have gotten some debris in the engine, even though I tried my best not to. That would cause low pressure, right? If there did happen to be debris in there. But if that were the case, wouldn't it be like that constantly, and not just when warmed up? I'm about to go pick up some more oil and filter, we'll see what happens. Thanks for all of the advice so far by the way, always appreciated!
 
Any debris small enough to make it past the pickup screen should be in the oil filter.

Buy a new filter, and 5 quarts of Rotella T 15w40. Drive it a little & watch the oil pressure.

.
 
I've had an oil pick-up full off nylon teeth from a factory cam gear that let go give an intermittent loss of oil pressure .

Dropped the pan ,cleaned out the pick-up, and problem solved.

Dissect the oil filter and check drained oil for any nylon particles ?
 
Getting mixed views on which viscosity to use...and it doesn't say in the manual. It just has suggestions. The weather here is about 40 in the mornings, 70's afternoons. Is there a "right" oil to use in these older cars?
 
Is it a more or less original 1974 engine?

If so, 15w40 or 20w50 should both be fine.

B.
 
I just put in some 5w-30, sorry didn't see the other post before I got there. It's running great now, oil pressure is back to normal. That was weird, I almost sharted when I saw it plummet this morning! I'm ready to take this girl for a ride! Plus, my wife will be home next weekend from Afghanistan, so I'll take her for a ride or two (in two different places, if you know what I mean!) haha. Anyway, thank you so much for all the input!
 
5-30 is alfulll thin for a old mopar. If its a new rebuild with real tight clearances maybe but stock original I would go with one of the 15-40 diesel oils. That said have had a oil filter collapse inside and cause a basicaly 0 oil pressure. My guess is your filter was to blame. I guess that there is a chance that any brand filter can fail but you can better your odds by sticking with a quality brand like Wix or peroilater.
 
Glad you got it back on the road. 5w30 should be fine.

I would say that it was not a filter failure. When that one happens the lifters all start to rattle, and you pretty much crap your pants.

If however this was an older engine with 40k of conventional oil use, you may have had a filter element full of junk the synthetic helped to dislodge. That means that at idle, the oil had to push past the bypass valve, losing as much as 10 psi in the process... So 15 psi looks like 5 on the gauge.

I agree that 30 weight oil is a little light for an older engine with some miles on it. You may well see "low" oil pressure at idle. Not an issue if the pressure swings right up off idle.

If you are staying with Mobil 1, they make both 5w40 & 15w50 oils. All the first number means is how it pumps when cold. Since you live in a mild climate, any of them are ok. If you lived farther north, the 0w40 might be a better choice for cold mornings.

The lower the cold viscosity, the less stress it puts on that oil pump drive on a cold start. Easily the weakest part of the LA engine as far as I am concerned. A cold start with a sump full of straight 50 oil causes the pump to work very hard, and can cause pressures to rise above the relief valve setting. If you have a 60 psi relief setting, and you see pressures above that on a cold start you should go to thinner oil.

B.

Edited to add:

Please thank your wife for her service. We really do appreciate what she does for this country.
.
 
Thanks for the advice bohica. I think I was just over reacting. I just took it out to make sure my kickdown was adjusted properly, and when the thermostat hit 195 at idle it went down to about 8 psi. At 2000 rpm, I was getting about 20 psi, and it jumped right up to it. Maybe I'll take a video, the gauges are right next to each other. Next oil change I'll put a heavier oil, but for now I think I should be OK. All I did was put a 4 barrel and intake, but I could have sworn I used to have more oil pressure even at idle.
 
Just went and looked at the mechanical gauge hose on the block. There was a little bit of oil seeping out of it. I think I found my culprit. Or, would that not cause it to do what it's doing? The gauge is pretty steady, but it's like as soon as it hits a certain temperature it just drops. I want to keep telling myself it's nothing to worry about, but then again, I don't want to fry my engine!
 
Fix that line, before it lets go & you have a big mess. It depends on how big the leak is, but probably not the cause.

You can put some Lucas additive in the crankcase to thicken that synthetic up a bit.

If the hydraulic lifters are getting enough oil to be quiet, you are doing fine. Just go a little thicker next oil change.

B.
 
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