Low Oil Pressure Q&A

[Jonnyuma]

I recently had an intake gasket failure that put water into my oil. Following some suggestions I got here one FBBO I doused the heads and lifter valley with clean diesel fuel until it ran clear-ish out of the oil pan drain, buttoned it up, added oil and a filter, and ran it for about 10 min. Drained it, fresh oil/filter and now my oil pressure is scary low. 50 psi on a cold start, but once it warms up its LOW. At 2000 rpm its at around 15-18, at idle in D it drops to 0 or so close to it that it doesn't matter. This thing pretty much lives at 1900-2000 rpm, which is my 20 mile each-way-to-work drive on a 45 mph two-lane (2000 rpm puts me at about 51 mph). The readings are off of a mechanical gauge. I'm not getting any strange noises (yet), but I'm wondering what may be causing this. I did use a cheap filter (Purolator) for the oil change, figuring on changing it out again after a week for my usual NAPA filter. If I'd known a filter could cause this I woulda just used the better one to start with. CAN a crapcan filter cause this?
This is on a stock 360 daily driven vehicle. No real racey stuff unless you count an Airgap intake and 4-bbl as racey. My buddy says "bring it over, we'll pull the motor and change the oil pump, water pump, timing chain, etc. Great, but his garage is 200 mi away, and I don't think I oughtta drive this car 200 mi with sub 20 psi oil pressure. 10w-40 in it now...heavier oil? Better filter? Shoot, I gotta git to work.

 

[terzmo]

I recently had an intake gasket failure that put water into my oil. Following some suggestions I got here one FBBO I doused the heads and lifter valley with clean diesel fuel until it ran clear-ish out of the oil pan drain, buttoned it up, added oil and a filter, and ran it for about 10 min. Drained it, fresh oil/filter and now my oil pressure is scary low. 50 psi on a cold start, but once it warms up its LOW. At 2000 rpm its at around 15-18, at idle in D it drops to 0 or so close to it that it doesn't matter. This thing pretty much lives at 1900-2000 rpm, which is my 20 mile each-way-to-work drive on a 45 mph two-lane (2000 rpm puts me at about 51 mph). The readings are off of a mechanical gauge. I'm not getting any strange noises (yet), but I'm wondering what may be causing this. I did use a cheap filter (Purolator) for the oil change, figuring on changing it out again after a week for my usual NAPA filter. If I'd known a filter could cause this I woulda just used the better one to start with. CAN a crapcan filter cause this?
This is on a stock 360 daily driven vehicle. No real racey stuff unless you count an Airgap intake and 4-bbl as racey. My buddy says "bring it over, we'll pull the motor and change the oil pump, water pump, timing chain, etc. Great, but his garage is 200 mi away, and I don't think I oughtta drive this car 200 mi with sub 20 psi oil pressure. 10w-40 in it now...heavier oil? Better filter? Shoot, I gotta git to work.

is it smoking ? burning oil? Blowby ? In the 60's when we had low oil pressure , outside of changing the oil pump, we'd go heavy oil. Try a straight 40 or 50 wt oil......and actually a product we used was stp and it was extremely thick but quieted an engine,stopped smoking,increased oil pressure. This may get you the 200 miles. By running the diesel until it was clear is too long. We used to run kerosene for a few minutes or less or until the motor knocked. You may need an entire build. Hope not,good luck.

 

[Jonnyuma]

No smoke or blow-by, and I never ran the engine with diesel in it. Just poured it through w the intake and valve covers off. I've heard of people doing that, but I didn't.

 

[Durandal25]

I recently had an intake gasket failure that put water into my oil. Following some suggestions I got here one FBBO I doused the heads and lifter valley with clean diesel fuel until it ran clear-ish out of the oil pan drain, buttoned it up, added oil and a filter, and ran it for about 10 min. Drained it, fresh oil/filter and now my oil pressure is scary low. 50 psi on a cold start, but once it warms up its LOW. At 2000 rpm its at around 15-18, at idle in D it drops to 0 or so close to it that it doesn't matter. This thing pretty much lives at 1900-2000 rpm, which is my 20 mile each-way-to-work drive on a 45 mph two-lane (2000 rpm puts me at about 51 mph). The readings are off of a mechanical gauge. I'm not getting any strange noises (yet), but I'm wondering what may be causing this. I did use a cheap filter (Purolator) for the oil change, figuring on changing it out again after a week for my usual NAPA filter. If I'd known a filter could cause this I woulda just used the better one to start with. CAN a crapcan filter cause this?
This is on a stock 360 daily driven vehicle. No real racey stuff unless you count an Airgap intake and 4-bbl as racey. My buddy says "bring it over, we'll pull the motor and change the oil pump, water pump, timing chain, etc. Great, but his garage is 200 mi away, and I don't think I oughtta drive this car 200 mi with sub 20 psi oil pressure. 10w-40 in it now...heavier oil? Better filter? Shoot, I gotta git to work.

also, please check the oil pressure sending unit sir. Is it a unit, or a line feed?

 

[Jonnyuma]

Mechanical gauge. I checked for leaks/cracks/holes but didn't find any. I changed the oil and filter this morning, used straight 30 wt but not much improvement. Still at about 18 psi @ 2000 rpm, drops to 0 at low idle when warmed up.
I was hoping for some external cause, but now I'm getting a little worried. I didn't have this problem before the intake gasket fiasco.

 

[krowbar]

Mechanical gauge. I checked for leaks/cracks/holes but didn't find any. I changed the oil and filter this morning, used straight 30 wt but not much improvement. Still at about 18 psi @ 2000 rpm, drops to 0 at low idle when warmed up.
I was hoping for some external cause, but now I'm getting a little worried. I didn't have this problem before the intake gasket fiasco.

maybe you got some sludge in the oil pick-up. I'd take the pan off and check. Or try a different gauge.

 

[Durandal25]

Mechanical gauge. I checked for leaks/cracks/holes but didn't find any. I changed the oil and filter this morning, used straight 30 wt but not much improvement. Still at about 18 psi @ 2000 rpm, drops to 0 at low idle when warmed up.
I was hoping for some external cause, but now I'm getting a little worried. I didn't have this problem before the intake gasket fiasco.

Jonny,

I would do a few things first, the very first would be to take the gauge out and clean the crap out of it. Getting sludge in there, and I'm sure you did, will hose your readings big time sir.

 

[Jonnyuma]

The funny thing about the capillary tubing (for the gauge) is that its EMPTY. I seem to remember it always having small oil bubbles in it before...so that's weird. The fitting was a little loose, so I tightened it down...no change there. I thought there might be some crud in the pickup/screen (that was actually my FIRST thought) but dropping the oil pan mid-week isn't possible, I'm not sure if its possible at all with the engine in the car. Just the same I put a new FederalMogul oil pump on will-call for tomorrow morning. An hour or so later...LIGHT BULB...called and ordered a pan gasket set too...duh.
I'm a little confused though...if I have 60+ psi at startup, that means the oil pump is at least ABLE to make pressure and get it to the top end, right? And some pressure drop is to be expected when the oil warms...but I watched the gauge drop from 40-ish at the start of my drive down to 18 or so about 5 miles in. The water temp holds steady at 180 degrees. The pressure rises and falls with engine rpm as it should, it just seems to be about 10 psi low once warmed up, and that's how I end up at 3-5 psi at low idle.

I don't want to go on and on...but I've searched the forums and found lots of good info (although sometimes scary) about sudden pressure losses, 0 psi at all rpm, catastrophic failures averted (or sometimes not), but not a whole lot about this particular problem. Thanks for the help with this, maybe there's some other cats that have the same issue that can benefit too.

 

[scotts74birds]

Just for perspective here, the newer Chrysler oil pressure senders trip at 4-6 psi. So is that really that bad as long as there is flow when rpm's come up?

 

[Jonnyuma]

Just for perspective here, the newer Chrysler oil pressure senders trip at 4-6 psi. So is that really that bad as long as there is flow when rpm's come up?

I hope not, Scott...its what I'm counting on until I can diagnose and fix the problem. I'm still driving it to work, but I put it in N whenever I have to stop to keep the rpm up over 1100-ish. I also let it idle for a little bit in P or N before I shut it down as my best effort at getting an oil film on everything for the next startup. I went so far as to buy a 2nd vehicle/parts chaser so I could do some more involved work without having to cut things short to put it all back together so I can get to work. Unfortunately Number 2 is a real POS and needs some work too, but I think I've got that covered this weekend.

 

[Albert Spangler]

Let's go back to basics here. You had good oil pressure before you changed the intake gasket and after changing the intake gasket, you don't have oil pressure. Most likely the oil pressure issue is related to changing the gasket. There are only two ways I can think of that changing the intake gasket would affect the oil pressure. The first is the oil pump drive didn't get hooked up. If that happened, the engine would be dead by now. The other is some gunk ended up somewhere it shouldn't have.

You said the engine isn't making any funny noises. I am assuming you are running hydraulic lifters. If the oil pressure is really getting as low as your gauge says, the lifters would be collapsing and rattling. As long as the lifters are not rattling, you should have enough oil pressure that nothing else will be damaged.

You said the gauge feed tube is empty. Have you taken the oil pressure feed fitting out of the block and made sure it is clear? That is my first guess at where the problem is. Also check and make sure the guage feed passage in the block is clear.

Everything you describe tells me that you actually have proper oil pressure. Your gauge just isn't seeing it. I have actually experience similar issues a couple of times over the years. Both times

 

[Jonnyuma]

At first I was worried about some crap getting dislodged and ending up in the pickup or a passage, like you mentioned. But the fact that the lifters are quiet, even when the needle drops, makes me think its something else. I've had the gauge tubing out of the fitting, but I haven't actually taken the fitting out, or checked the back of the gauge itself. That's where I think I'll start next.

Thanks.

 

[brasil]

...change the oil...and the filter.... go for 20W50 weight oil ( Lucas Oil for example ) and use a GOOD Filter Wix, K&N ...
give it a try..... 50 bucks or so... is worth it

Good Luck
Juergen

P.S Change the oil while it is still real hot..to get rid of the sludge (if there is any..)

 

[YoungMopar]

I HAVE THE SAME PROBLEM.... 74 RR built 360. camshaft broke driving, (sat 17 years) pulled motor. rebuilt it, added melling high volume oil pump, still have low pressure at gauge...been trying to diagnose it but another problem arose. good luck to you my friend, ive exhausted every option

 

[2fuzy]

first determine what your oil pressure actually is put a different guage on it
if the pressure is dropping that low as it warms up you probally need bearings in the bottom end