No/Low Oil Pressure

[SCB2525]

96 XLT 4.0 OHV, 186k

The oil pressure gauge plummeted to nothing one day despite no noises or sharp increases in temp. So I keep driving it and the gauge keeps fluctuating between normal and nothing. A bit and later, I start to hear a bit of light rattling conducive to low oil pressure, but not no oil pressure. I pulled over and sat for a while and tried it again, and pressure was fine, and the rattling gradually went away. Then it happened again and I kept stopping and going until I got home. I changed the oil out from some Quaker State synth with about 2k on it with 4 quarts of Quaker State 10w-40 dino and a quart of MMO. First, after a test drive, all was well and then it plummeted again. So I've been driving it because I have no choice and its odd. It will go for tens of miles without issue and then randomly do it again for a time, and randomly come and go. It seems the longer I let it sit, the less likely it is to do it for a while.

This has happened before but was "cured" with a simple oil change, which I presumed was a clogged filter. That was a few years ago.

So what are you're thoughts? I honestly can't justify doing anything involving removing the engine, considering it would probably cost more than the truck is worth.

 

[rhauf]

96 XLT 4.0 OHV, 186k

The oil pressure gauge plummeted to nothing one day despite no noises or sharp increases in temp. So I keep driving it and the gauge keeps fluctuating between normal and nothing. A bit and later, I start to hear a bit of light rattling conducive to low oil pressure, but not no oil pressure. I pulled over and sat for a while and tried it again, and pressure was fine, and the rattling gradually went away. Then it happened again and I kept stopping and going until I got home. I changed the oil out from some Quaker State synth with about 2k on it with 4 quarts of Quaker State 10w-40 dino and a quart of MMO. First, after a test drive, all was well and then it plummeted again. So I've been driving it because I have no choice and its odd. It will go for tens of miles without issue and then randomly do it again for a time, and randomly come and go. It seems the longer I let it sit, the less likely it is to do it for a while.

This has happened before but was "cured" with a simple oil change, which I presumed was a clogged filter. That was a few years ago.

So what are you're thoughts? I honestly can't justify doing anything involving removing the engine, considering it would probably cost more than the truck is worth.

It sounds to me like there is a problem with the oil pump pick-up tube. if it were me, i'd drop the pan (or pull the engine if need-be) and change/inspect the oil pump and pickup tube. the tube could be loose from the pump and letting air in, when the pump is sucking air, it wont build pressure and thats you're low oil pressure.

and i'm not sure i fallow that removing the engine would "cost more than the truck is worth" it never costs me anything to remove an engine. disconnect it, hoist it out.. costs nothing but a couple hours of time.

if you're really lazy and don't want to take the engine out, you could try over-filling the oil by a couple quarts and see if that makes the problem go away. remember, any time an engine runs without oil, even for only a moment at a time, there is metal-to-metal contact in you're bearings and they can be destroyed in very, very short order (i lost oil pressure once and the engine lasted less than a minute before seizing with 3 spun bearings)

the OHV 4.0 is a very reliable engine, if you fix the oil pump it should serve well for a long time.

 

[RickMar]

I would say you are having an issue with your oil pressure sending unit.
I have heard they are commonly known "to bite the dust".

I have a 1999 Mountaineer 5.0L 186,000 miles and the same thing (except for the noise) happened to me about 3 years ago. At first I was a little on edge thinking my oil pump bombed out on me. The oil pressure gauge still goes ballistic now and then and eventually works fine. But at least I know exactly what the issue is.

I would check or replace the sending unit...short money to get rid of the worry.
Also, catch it early just in case there is something major going on.

Good Luck;
Rick

 

[SCB2525]

I really don't think its the sending unit. I did replace it when it read no pressure all the time sometime earlier than when this first started a few years ago and the unit worked after that. Plus, the rattling that comes with extended periods of "no pressure" according to the gauge is definitely low-pressure valve-train noise.

I'm not pulling the engine. I can't do it myself and I can't afford to have it done. Plus, I don't even know if its a mechanical problem because why would it stop for a good 3 years and then pop back up with the same low-pressure and rattling? I'm thinking something might be plugged.

Would overfilling it cause any harm?

 

[rhauf]

I really don't think its the sending unit. I did replace it when it read no pressure all the time sometime earlier than when this first started a few years ago and the unit worked after that. Plus, the rattling that comes with extended periods of "no pressure" according to the gauge is definitely low-pressure valve-train noise.

I'm not pulling the engine. I can't do it myself and I can't afford to have it done. Plus, I don't even know if its a mechanical problem because why would it stop for a good 3 years and then pop back up with the same low-pressure and rattling? I'm thinking something might be plugged.

Would overfilling it cause any harm?

i highly doubt there is something plugging it. that is extremely unlikely. even if something was plugging it, it would be consistent, not fluctuating as you describe. you can run a couple extra quarts (id say two, max) without hurting anything. if you don't want to fix it then i'd recommend selling before it's ruined and leaves you stranded somewhere. oh. and tell the buyer it needs a new oil pump.

 

[Spdrcer34]

i highly doubt there is something plugging it. that is extremely unlikely. even if something was plugging it, it would be consistent, not fluctuating as you describe.

REALLY? State your source? Just because YOU have never seen, doesn't mean it is "extremely unlikely". As a matter of fact it is VERY likely. And a blockage in the system WOULD cause a fluctuation as described.



I had a oil pressure drop issue while offroading this last summer.

As it turns out, the combination of the TERRIBLE bumpy Forest Service Roads and the fresh oil was a bad combination. The end result was oil build up in the valve covers, and in all the passages broke free, and caused them to clog up the Oil Pick-up screen.

I had oil pressure below 1200 or so, but above that I had NOTHING. But I was still able to drive it home...I did have a clatter that I thought was going to eat the engine from the inside out.

Zero oil pressure and Zero noise COULD be the sending unit.
Zero oil pressure AND noise is NOT the sending unit. It's a failure in lubrication system.

Ryan

 

[rhauf]

REALLY? State your source? Just because YOU have never seen, doesn't mean it is "extremely unlikely". As a matter of fact it is VERY likely. And a blockage in the system WOULD cause a fluctuation as described.



I had a oil pressure drop issue while offroading this last summer.

As it turns out, the combination of the TERRIBLE bumpy Forest Service Roads and the fresh oil was a bad combination. The end result was oil build up in the valve covers, and in all the passages broke free, and caused them to clog up the Oil Pick-up screen.

I had oil pressure below 1200 or so, but above that I had NOTHING. But I was still able to drive it home...I did have a clatter that I thought was going to eat the engine from the inside out.

Zero oil pressure and Zero noise COULD be the sending unit.
Zero oil pressure AND noise is NOT the sending unit. It's a failure in lubrication system.

Ryan

my source is my own experience. I'm pretty sure thats all any of us here have to offer, as this is not a place for facts, but a place where we can give recommendations based on personal experience. if this is the case, and oil return passages are blocked, he should run a lightweight high detergent oil (or synthetic, maybe with a little ATF mixed in) to clean it up. also i'd think his oil when he changes it would come out sludgy from the crap it picks up if the engine is really that gunked up inside.

either way, he would have to take his engine out/apart or do more work than he is willing to do in order to fix it right, and since he's not willing to work on the engine internals (which require extracting the engine) it's really sort of a moot point unless pouring something in will fix it.

by the way, quakerstate oil is in fact a sludgy oil, has more parafin or something in it.. i'd run castrol or something.

 

[rhauf]

double post.

 

[2000StreetRod]

clogged returns

I burned up the engine in my Grand Cherokee V8 with similar symptoms. I drove for a while on the freeway and the oil pressure dropped. I pulled over as soon as I could and checked the dipstick. The oil level was fine. I drove home and replaced the oil pressure sending unit. Later the same thing happened again so I drove it to the local dealer since I was in the process of moving from Georgia to South Carolina. About two miles from the dealer I began to hear noisy lifters. It turned out that the oil returns in the head were clogged so after driving for a while all of the oil was in the heads and there was none for the pump to pick up in the sump. Ended up costing $5,000 for a remanufactured engine and installation. Since then I do an engine flush before every other oil change.

 

[SCB2525]

What is everyone's thoughts on an engine flush in-a-bottle like Seafoam? I'm at the point where the risk is somewhat negated by the fact that the engine might grenade itself anyway at any time.

Also, what is the pressure threshold at which these dummy gauges goes to nothing? I remember it being somewhere in the lower single-digits.

 

[TooManyTrucks]

My 95 had the same fluctuating gauge. I checked pressure with a real gauge..it was fine. I replaced the sending unit...it turned out to be a short in the wireloom...

Seafoam is good stuff. Make sure your thermostat is hot enough otherwise these engines do sludge up if they don't get to operating temps.

 

[SCB2525]

You know, now that you mention it I have had the suspicion that my thermostat might be stuck open for a while. The temp gauge never goes past half-way and rarely goes beyond 1/4-1/3 of the way up.

Maybe a thermostat replacement and a seafoam-in-the-crankcase round is the way to go.

 

[Spdrcer34]

`foam it!

Buy 2 cans.

Pour 1 can in the crankcase. Run the motor up to operating temp. While you're doing that, suck half of a can into the engine through the vacuum line on the throttle body. Pour the other half of the can in the gas tank.

Let the engine cool down, and change the oil.

Ryan

 

[SCB2525]

Why let the engine cool down? I'd think I would want to change it while all the crap is warm and suspended?

 

[SCB2525]

Anyway, I decided to try Amsoil's engine flush since I've read much better reviews of it as opposed to Seafoam when being used in a full-can dose. Not sure when I'll actually flush it but I'll check back here with results.

 

[SCB2525]

Well now, today I started it to move it into my garage and the gauge never moved at all. Pulled it in, changed the filter, put in the flush, ran it for like 30 mins, gauge never moved. Not only that but now its knocking and ticking. So, I'm at wit's end; I don't know what to do. I don't have the tools or know-how to drop the pan myself or the resources to have someone else do it.

It seems my Explorer isn't long for this world.