Low Oil Pressure (Not The Sensor)

Pull the oil fill cap and look down in there for signs of a crack/coolant or mixing of the coolant and oil. I think if you have the engine running you’ll possibly see it if it‘s cracked and leaking.
 
If I thought my head was cracked I might send the oil out to a place like Blackstone Labs and have them check it. Coolant in the oil isn't great for anything. Normally you'd run warm and loose coolant but you never know if you just got it. I think the crack should be visible after the engine is warm through the valve cover like @MountaineerTom says.
 
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MountaineerTom said:
Pull the oil fill cap and look down in there for signs of a crack/coolant or mixing of the coolant and oil. I think if you have the engine running you’ll possibly see it if it‘s cracked and leaking.
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Inconclusive.

MAYBE there's a teeny tiny little bubble every second or so coming from the driver side under the oil fill cap, but you really have to want to see something. It's not even the size of the smallest champagne bubble you've ever seen. And there doesn't appear to be a green tinge from coolant either.
 
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RedWranglerRedWrangler said:
Inconclusive.

MAYBE there's a teeny tiny little bubble every second or so coming from the driver side under the oil fill cap, but you really have to want to see something. It's not even the size of the smallest champagne bubble you've ever seen. And there doesn't appear to be a green tinge from coolant either.
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Maybe it's just enough to cause your issues.

Were you able to see the TUPY molded into the head when looking through the oil fill hole to confirm if you have the head that's prone to cracking?
 
Welp just cleaned out the port with a brass tube brush & blasted 1qt of oil out of the hole, then checked myself with a mechanical oil pressure tester and saw 0psi at hot idle. I don't know how that happens without any other noises / symptoms but there ya go.

Guess all I can do is keep up with oil changes and try to keep this thing alive as long as possible.
 
RedWranglerRedWrangler said:
Welp just cleaned out the port with a brass tube brush & blasted 1qt of oil out of the hole, then checked myself with a mechanical oil pressure tester and saw 0psi at hot idle. I don't know how that happens without any other noises / symptoms but there ya go.

Guess all I can do is keep up with oil changes and try to keep this thing alive as long as possible.
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Amazing!,im a 4.0 I don’t need no stinking oil pressure!,im speechless don’t know what to tell you to do at this point?was hoping for better news,sorry man
 
Don't confuse pressure with flow.
It's not practical to measure oil flow, so they rely on a pressure reading.
If you are confident that the pump is functioning (you would definitely know it if there was no oil being pumped to the top end), then I would start by checking the electrical connections at the sending unit. Wires in the engine compartment get brittle with age, and can be responsible for a ton of other 'apparent' issues.

If you were losing oil pressure due to internal engine issues, then you would likely see smoke in the exhaust, oil in the water, water in the oil, etc.
 
WestCoastDan said:
Don't confuse pressure with flow.
It's not practical to measure oil flow, so they rely on a pressure reading.
If you are confident that the pump is functioning (you would definitely know it if there was no oil being pumped to the top end), then I would start by checking the electrical connections at the sending unit. Wires in the engine compartment get brittle with age, and can be responsible for a ton of other 'apparent' issues.

If you were losing oil pressure due to internal engine issues, then you would likely see smoke in the exhaust, oil in the water, water in the oil, etc.
Click to expand...
Not sure I understand. I bypassed any potential electrical causes by screwing in a mechanical oil pressure tester directly to the engine. I don't have any smoke in the exhaust, or oil in water / water in oil as far as I can tell.

Only other things I can think are that 1) my mechanical oil pressure tester isn't sensitive enough and I'm getting like 2 psi or something, enough to circulate oil, but not enough to register or 2) the oil pressure port is located such that it can't pick up pressure below a certain level. I don't know kinda grasping at straws here
 
The oil port will read single digit pressures just fine, so you def have an oil pressure issue.

You could have a bad oil pump or a clogged pick up screen.

You might be able to limp it along awhile with a high volume oil pump if the bearings are truly causing the loss of oil pressure.
 
I'm going to bet that your 0331-cylinder head is has a small crack and has been leaking coolant into the engine for a while. If I remember correctly, the area in which it cracks allows coolant to reach the cam bearings. I think it's the #2 or3 cam bearing that gets wiped.
The reason you have no engine noise is because the oil pressure is bleeding out the cam bearing and not the bottom end (mains/rods).
Unfortunately, Mopar's diagnostic flow charts and schematics suck compared to GM.
But if you get yourself a pressure gauge and an adapter.... you can diagnose this.
You need to check you oil pressure @ the oil filter. You need an adapter to do this. See below. You may be able to obtain it at an autozone that lends tools.
Then you need to remove the oil pressure sensor and install the pressure gauge at the port and record it.
The oil pressure at the oil filter and at the sensor port should be within a few pounds of one another.
If the oil pressure at the filter adapter is 30-40 psi, but the pressure at the sensor port is much lower, it's due to the cam bearings being wiped. You have oil pressure down low, but low to no pressure up top.




https://www.amazon.com/dp/B0002SQWY8/?tag=wranglerorg-20
 
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williambmac said:
I'm going to bet that your 0331-cylinder head is has a small crack and has been leaking coolant into the engine for a while. If I remember correctly, the area in which it cracks allows coolant to reach the cam bearings. I think it's the #2 or3 cam bearing that gets wiped.
The reason you have no engine noise is because the oil pressure is bleeding out the cam bearing and not the bottom end (mains/rods).
Unfortunately, Mopar's diagnostic flow charts and schematics suck compared to GM.
But if you get yourself a pressure gauge and an adapter.... you can diagnose this.
You need to check you oil pressure @ the oil filter. You need an adapter to do this. See below. You may be able to obtain it at an autozone that lends tools.
Then you need to remove the oil pressure sensor and install the pressure gauge at the port and record it.
The oil pressure at the oil filter and at the sensor port should be within a few pounds of one another.
If the oil pressure at the filter adapter is 30-40 psi, but the pressure at the sensor port is much lower, it's due to the cam bearings being wiped. You have oil pressure down low, but low to no pressure up to.




https://www.amazon.com/dp/B0002SQWY8/?tag=wranglerorg-20
Click to expand...
100% this.
 
Richard49 said:
100% this.
Click to expand...
williambmac said:
I'm going to bet that your 0331-cylinder head is has a small crack and has been leaking coolant into the engine for a while. If I remember correctly, the area in which it cracks allows coolant to reach the cam bearings. I think it's the #2 or3 cam bearing that gets wiped.
The reason you have no engine noise is because the oil pressure is bleeding out the cam bearing and not the bottom end (mains/rods).
Unfortunately, Mopar's diagnostic flow charts and schematics suck compared to GM.
But if you get yourself a pressure gauge and an adapter.... you can diagnose this.
You need to check you oil pressure @ the oil filter. You need an adapter to do this. See below. You may be able to obtain it at an autozone that lends tools.
Then you need to remove the oil pressure sensor and install the pressure gauge at the port and record it.
The oil pressure at the oil filter and at the sensor port should be within a few pounds of one another.
If the oil pressure at the filter adapter is 30-40 psi, but the pressure at the sensor port is much lower, it's due to the cam bearings being wiped. You have oil pressure down low, but low to no pressure up to.




https://www.amazon.com/dp/B0002SQWY8/?tag=wranglerorg-20
Click to expand...

Very very interesting. This is the only explanation I've seen for how the vehicle's conditions are even possible. I'm curious to do this diagnosis, but wonder if it would change the solution at this point already — an engine rebuild / replacement?

If I perform the diagnosis and determine it's the cam bearing(s) and head/gasket, is the pragmatic solution for that also an engine rebuild / replacement?
 
WestCoastDan said:
Don't confuse pressure with flow.
It's not practical to measure oil flow, so they rely on a pressure reading.
If you are confident that the pump is functioning (you would definitely know it if there was no oil being pumped to the top end), then I would start by checking the electrical connections at the sending unit. Wires in the engine compartment get brittle with age, and can be responsible for a ton of other 'apparent' issues.

If you were losing oil pressure due to internal engine issues, then you would likely see smoke in the exhaust, oil in the water, water in the oil, etc.
Click to expand...
Sorry, this is completely wrong. You are conflating blown head gasket symptoms with low oil pressure problems.
 
RedWranglerRedWrangler said:
Very very interesting. This is the only explanation I've seen for how the vehicle's conditions are even possible. I'm curious to do this diagnosis, but wonder if it would change the solution at this point already — an engine rebuild / replacement?

If I perform the diagnosis and determine it's the cam bearing(s) and head/gasket, is the pragmatic solution for that also an engine rebuild / replacement?
Click to expand...
The head will have to be removed and pressure tested. Cam bearings, and cam, if bad need to be replaced. Before all that a compression test would help indicate how far you would need to go. You may get by with just a head and cam bearings. (If the cam isn’t wiped out) Personally I would always go for a rebuild over replacement but then I do all the work myself. If you’re not doing the work, and the engine’s condition indicates a need for rebuild, I think a reman engine would be the wisest path.
 
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