Low oil pressure?

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I’m going to throw this way out there -

How’s the alternator, regulator, and battery? Full system voltage? I’ve had a mopar or two where the idle was so poor or the system voltage too low - enough to change indication.

You have one of these traits - it happens at idle.

I’ve also had a wiring problem to the pressure sending unit where the unit connector was simply loose on that little nail head they give you to wire it up. Thinking back, it had a pretty consistent on/off cycle to it. It was a nice RamCharger, too. 318 >100k so if it wasn’t ticking, it had oil pressure.

Something else to check.
 
Cope said:
My new engine is having an oil pressure issue.

At idle I make 25psi hot, 50PSI at 1000 rpm and 65+ above 2000 rpm.

I've been doing some freeway testing and after 15 min at around 2,500-2,000 RPM I got off the free way and oil pressure dropped to almost zero. We're not talking hard on the breaks or down hill just sitting at the light. I put my foot in it to bump it up back to 25 so it was not idling at zero. Twice now I've seen it do this.

HV pump running 20-50 Joe Gibbs oil.
Factory car pan.

Maybe 200 miles on a full build.
Balance, blueprint the whole nine yards.

I'm on my second oil change, I drained it at about 100 miles and cut the filter just to make sure all was well. No metal in the filter.

11.5-1 comp ratio.
Big lumpy cam (dont have the specs on hand)

Any ideas, I'd hate to pull the engine again but I also dont want to ruin my new engine...

Engine was built at a very good, high performance machine shop.
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I see a few things here. 25 psi hot @ probably 600-800 rpm is pretty low given all the rest. When running on the freeway in the summer especially, the oil gets pretty hot and viscosity drops of course. I bet your lifter bores are on the worn side, and other bearing clearances are on the loose side-combine this with 20w/50 being pumped by an HV pump and sustained rpm all you are seeing is HOT oil and idle speed pressures. You can try more oil but that won't likely solve your issue. Also a pickup that is too far off the bottom would show momentary low oil pressure but recover within a few seconds-same with a cracked p-u tube.

I believe the root cause is oil leaking internally , too much. J.Rob
 
J.rob, wouldn’t highway speed cause lower oil temps? It doesn’t take much power at all to cruise the highway with all that nice cool air to flow through the engine bay, across the oil pan, where oil gets cooled the most.

idling at a stoplight would heat the oil up much much faster.

I wonder why the builder put the HV pump in and tell him to run 20w50. Must have been with reason. High bearing clearance, shaft style rockers, race use, something.


Another thing to check would be the filter again. If it’s getting clogged, pressure indication will lower. Cut the filter you have on now open and see what’s going on.
 
T56MaxTorq said:
J.rob, wouldn’t highway speed cause lower oil temps? It doesn’t take much power at all to cruise the highway with all that nice cool air to flow through the engine bay, across the oil pan, where oil gets cooled the most.

idling at a stoplight would heat the oil up much much faster.

I wonder why the builder put the HV pump in and tell him to run 20w50. Must have been with reason. High bearing clearance, shaft style rockers, race use, something.


Another thing to check would be the filter again. If it’s getting clogged, pressure indication will lower. Cut the filter you have on now open and see what’s going on.
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Doesn't work like that. Sustained RPM = high oil temp. J.Rob
 
Cope said:
So maybe I should try adding like a half a quart more oil?
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IMHO, you should absolutely do this as an experiment to test the theory of the pickup being too high. With the stock pickup being up .3" off the pan, you lose about 1/2 quart of oil that can be picked up.

If this erratic pressure issue goes away, then you have answered the question. If the issue stays the same, and you don't have any missing plugs anywhere, then it is likely the clearance issue.

If I may ask the question once again, when you exit the freeway and come to a stop and the pressure is low, does it stay low for as long as you stay stopped and idling? Or does the pressure just drop low for a few seconds and then come back up while you are stopped and idling? That answer may tell us more about the specific issue.
 
T56MaxTorq said:
J.rob, wouldn’t highway speed cause lower oil temps? It doesn’t take much power at all to cruise the highway with all that nice cool air to flow through the engine bay, across the oil pan, where oil gets cooled the most.

idling at a stoplight would heat the oil up much much faster.
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Much/most of the heat in the oil comes from the heat in the pistons, which goes up with the power being generated, even at cruise.

I was watching my oil temp gauge on the CTD towing a 20' trailer in I-64 through the mtns of WV last week. Going up the mtns, the oil temp would rise to the 220*. As soon as I started downhill, the oil temps would drop like a rock; they would drop 50-60 degrees with a 45 second steep downhill run. That change is overly extreme versus our typical small blocks, what with the biiig oil cooler (plus a big turbo with oil flow in it) in that truck but it illustrated the correlation of oil temps with combustion power.
 
nm9stheham said:
Post #69 is a good answer, with the addition of the note that the 3/8" is for aftermarket pickups that pick up through the bottom.
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If it was the pickup location and oil level then when he put his foot in it to bring pressure up--guess what? It wouldn't come up but the RPM's would. J.Rob
 
nm9stheham said:
Much/most of the heat in the oil comes from the heat in the pistons, which goes up with the power being generated, even at cruise.

I was watching my oil temp gauge on the CTD towing a 20' trailer in I-64 through the mtns of WV last week. Going up the mtns, the oil temp would rise to the 220*. As soon as I started downhill, the oil temps would drop like a rock; they would drop 50-60 degrees with a 45 second steep downhill run. That change is overly extreme versus our typical small blocks, what with the biiig oil cooler (plus a big turbo with oil flow in it) in that truck but it illustrated the correlation of oil temps with combustion power.
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That’s a turbo diesel truck pulling a load up a grade, not an A-body cruising the highway. You’re probably producing over 400 ft. Lbs while he’s producing <50 and not trying to oil cool a turbo.

I’m not really convinced that hot engine oil in a 45yo car idling while stopped after a highway cruise would become cooler. It’s a mute opinion anyways and probably not the problem. I’d doubt a 10,20, or 30 degree change in oil temp could drop the pressure so drastically. It especially wouldn’t drop it to zero.

Cope never told us what type of oil gauge he has. Electric or manual. If it’s a manual gauge, could have too much entrapped air in the lines causing some of these issues. Probably needs to be a significant amount of air tho cause everyone has a couple bubbles.
 
I've installed 2 oil temp gauges in older vehicles and my 2011 RAM has this information along with trans temp. Highway driving @ 1800 rpm and the oil gets hot--get off highway oil cools off. It's not a moot opinion its a fact backed up by multiple observations of this many times. This is especially true when on the dyno. Let the engine idle and oil temp will never come up. Put 2000 rpm and some light load on it @ 60-80 hp and oil will come up relatively fast. I've seen 70-80 cold idle pressure drop to 15 or so when oil is hot--this happens when clearances are loose. The HV pump and thick oil are actually exasperating the problem. Don't believe me? Don't care. Hook up a gauge, see for yourself. J.Rob

p.s. It's not air in the line either.
 
The gauge is electric automeeter.

I'm leaving town tonight so not sure how much time I'll have to mess with it.
 
I will say this. That very plug under the main cap was left out by my builder. Luckily he recognized his error and called me before I buttoned the engine up. You never know when a professional is having a bad day (we all have the occasional brain fart) By the way, it is pressed in and you have to remove the pump and main cap to access it. I just removed one from an old block I had laying around.
 
superchargeddrt said:
I will say this. That very plug under the main cap was left out by my builder. Luckily he recognized his error and called me before I buttoned the engine up. You never know when a professional is having a bad day (we all have the occasional brain fart) By the way, it is pressed in and you have to remove the pump and main cap to access it. I just removed one from an old block I had laying around.
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That plug only forces the oil thru the filter. It will not impact pressure. J.Rob
 
RAMM said:
I've installed 2 oil temp gauges in older vehicles and my 2011 RAM has this information along with trans temp. Highway driving @ 1800 rpm and the oil gets hot--get off highway oil cools off. It's not a moot opinion its a fact backed up by multiple observations of this many times. This is especially true when on the dyno. Let the engine idle and oil temp will never come up. Put 2000 rpm and some light load on it @ 60-80 hp and oil will come up relatively fast. I've seen 70-80 cold idle pressure drop to 15 or so when oil is hot--this happens when clearances are loose. The HV pump and thick oil are actually exasperating the problem. Don't believe me? Don't care. Hook up a gauge, see for yourself. J.Rob

p.s. It's not air in the line either.
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Relax Rob, it’s my opinion that is moot, not yours. I believe your truck gauge but we’re not talking trucks and most definitely not dynos, nor a cold engine startup and idle. What I’m saying is that with a hot engine on the highway, cruising, which you personally observe causes hot oil, the oil temp will rise when you take cooling airflow away, like when you pull off the highway and immediately stop.

As for air in the line - it has to be a lot of air. It will cause problems. Mostly the gauge will be slow to respond and cause minor inaccuracies. Boyle’s law says so.
 
T56MaxTorq said:
Relax Rob, it’s my opinion that is moot, not yours. I believe your truck gauge but we’re not talking trucks and most definitely not dynos, nor a cold engine startup and idle. What I’m saying is that with a hot engine on the highway, cruising, which you personally observe causes hot oil, the oil temp will rise when you take cooling airflow away, like when you pull off the highway and immediately stop.

As for air in the line - it has to be a lot of air. It will cause problems. Mostly the gauge will be slow to respond and cause minor inaccuracies. Boyle’s law says so.
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So idle speeds and loads = hot oil 'cuz no airflow. Okey Dokey. OP says electric so there goes the air theory J.Rob
 
hey jabroni you can argue and disagree all you want but your wrong plain and simple . I think that's 3 professional engine builders and a couple of others damn you are hard headed .
 
jimjimjimmy said:
hey jabroni you can argue and disagree all you want but your wrong plain and simple . I think that's 3 professional engine builders and a couple of others damn you are hard headed .
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Well that's three professional engine builders and a couple of others that I wouldn't ever let touch my engines.
 
Why don't you try a straight weight oil say 40 wt and see if you still have the problem, btw what brand of oil are you using?
 
RAMM said:
That plug only forces the oil thru the filter. It will not impact pressure. J.Rob
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If this is true and the absence of that plug just allows unfilter oil to circulate, why do those motors eat their bearings and in such a short period that its not just dirty oil. I agree that the plug does divert
Oil to the filter, but it also alters how much oil is seen through out the motor. Without the plug they will show pressure, but I wouldn’t feel comfortable saying it couldn’t show on the guage. Pull tge sending unit stick the rod in and eliminate that possibility.
 
furrystump said:
If this is true and the absence of that plug just allows unfilter oil to circulate, why do those motors eat their bearings and in such a short period that its not just dirty oil. I agree that the plug does divert
Oil to the filter, but it also alters how much oil is seen through out the motor. Without the plug they will show pressure, but I wouldn’t feel comfortable saying it couldn’t show on the guage. Pull tge sending unit stick the rod in and eliminate that possibility.
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Without the plug the engine would see MORE oil flow. Filters are quite restrictive, plus more 90 degreee turns to get into and out of it. Dirt is the number one killer of bearings-talk to any bearing rep. J.Rob
 
I agree, dirt kills bearings, but I have seen three of four of this exact plug out failures the die in 2-3 hours of run time. Motors built in clean enviroments. I can’t imagine dirt is killing these bearings in that short of a period.
 
Thinking about it, at 6500 rpm at the stripe I’m sure the bypass is open on my oil pump. My motor spends a good deal of its life with oil by passing the filter.
 
RAMM said:
Without the plug the engine would see MORE oil flow. Filters are quite restrictive, plus more 90 degreee turns to get into and out of it. Dirt is the number one killer of bearings-talk to any bearing rep. J.Rob
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Right... the oil would flow straight up into the passenger side gallery rather than make several added tight turns in/out of the filter. They're all pressure drops.....
With the plug out, anyone thinking that the oil will flow backwards into the filter needs to say where is the lower pressure area inside the filter or in the filter passages, to where any oil can divert away from the engine. As said, once air is purged out of what is now a useless side passage and filter filled with oil, the filter and its passages just 'dissappear' from the oiling system.
(And I am not seeing what bearings wearing out has anything to do with this....)
A diagram would perhaps help.....but back to work for me. Dang... I thought I was done with this LOL
 
furrystump said:
Thinking about it, at 6500 rpm at the stripe I’m sure the bypass is open on my oil pump. My motor spends a good deal of its life with oil by passing the filter.
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I think you are missing the bypass function. The bypass is in the oil pump. When it starts bypassing, it moves a valve that dumps excess pressure into the intake side of the pump, returning to the pump. No oil " bypasses the filter " to the engine, .
 
inertia said:
I think you are missing the bypass function. The bypass is in the oil pump. When it starts bypassing, it moves a valve that dumps excess pressure into the intake side of the pump, returning to the pump. No oil " bypasses the filter " to the engine, .
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ok, like you said, looking at the oil path diagram I don’t see how it could change the oil flow. I guess with the extra new engine debris that usually shows up at the first oil change could be enough.
 
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