Low oil pressure after engine is hot

[Leebo24]

Good evening. Brand new to the forum. Hoping to get some help. Bought 2005 Rubicon about a year ago. 129K miles. 4.0 L inline 6 motor. Six speed manual transmission. Runs great. Just last night, oil pressure gauge dropped to zero at idle. This occurred after running down the highway for 25-30 minutes at 65 MPH. Motor did not run rough or show any signs of an issue. Jeep ran perfectly the entire trip. As I pulled away from red light and increased RPM’s gauge went back to normal. Next time I stopped, gauge did the same thing. I tapped the throttle, the gauge went back to normal, but quickly dropped to zero again as I let motor idle. No sign of an oil leak anywhere. Let Jeep sit for about an hour and a half. Gauge acted normal. Ran down highway again … low pressure again. Any help would be appreciated. I hear possibly oil pressure sending unit needs replaced. I know oil pressure is going to fluctuate, but gauge moved very little at stops prior to
this.

Thanks in advance. Will post pictures once I figure out how to do so.

 

[TexasTJ2004]

2005 does not have a real gauge, it is a pressure switch, like it has 2 states, under 9PSI or above.
Either your pressure switch sensor went bad, or the oil pressure dropped under 9PSI

 

[Leebo24]

Good evening. Brand new to the forum. Hoping to get some help. Bought 2005 Rubicon about a year ago. 129K miles. 4.0 L inline 6 motor. Six speed manual transmission. Runs great. Just last night, oil pressure gauge dropped to zero at idle. This occurred after running down the highway for 25-30 minutes at 65 MPH. Motor did not run rough or show any signs of an issue. Jeep ran perfectly the entire trip. As I pulled away from red light and increased RPM’s gauge went back to normal. Next time I stopped, gauge did the same thing. I tapped the throttle, the gauge went back to normal, but quickly dropped to zero again as I let motor idle. No sign of an oil leak anywhere. Let Jeep sit for about an hour and a half. Gauge acted normal. Ran down highway again … low pressure again. Any help would be appreciated. I hear possibly oil pressure sending unit needs replaced.

Thanks in advance. Will post pictures once I figure out how to do so.

 

[macleanflood]

Go to any parts store and "rent" an oil pressure gauge...you'll disconnect your sensor and use whatever adapters you need to get to 1/8". I bought one on Amazon. I like to run mine out the hood so I can watch it as I drive.

If/when you replace your sensor use a Mopar. I've heard some folks have luck with Standard. I went through bunches till I bought a Mopar.

Good luck! Tons of forum posts on this subject.

-Mac

 

[macleanflood]

Just posted this to essentially the same question.

Go to any parts store and "rent" an oil pressure gauge...you'll disconnect your sensor and use whatever adapters you need to get to 1/8". I bought one on Amazon. I like to run mine out the hood so I can watch it as I drive.

If/when you replace your sensor use a Mopar. I've heard some folks have luck with Standard. I went through bunches till I bought a Mopar.

Good luck! Tons of forum posts on this subject.

-Mac

 

[TheBoogieman]

I went through that a few months ago. Buy a Mopar oil pressure sensor.

 

[Leebo24]

Thank you all for the replies. Any reason it only happens when hot? Also, if oil pressure is actually dropping, why would that be happening?

 

[TheBoogieman]

Thank you all for the replies. Any reason it only happens when hot? Also, if oil pressure is actually dropping, why would that be happening?

The sensor is just screwing up the signal. I was too lazy to test my oil pressure. I bought a new Mopar sensor for $35 on Amazon. Fixed my issue in 10 minutes.

 

[Leebo24]

The sensor is just screwing up the signal. I was too lazy to test my oil pressure. I bought a new Mopar sensor for $35 on Amazon. Fixed my issue in 10 minutes.

Just ordered Mopar sensor from Rock Auto. Will change and post results.

 

[TheBoogieman]

Duplicate thread.

 

[Leebo24]

Just ordered Mopar sensor from Rock Auto. Will change and post results.

New sensor is in. Waiting to go on long ride and get motor hot to see if new sensor fixes issue.

 

[Leebo24]

The sensor is just screwing up the signal. I was too lazy to test my oil pressure. I bought a new Mopar sensor for $35 on Amazon. Fixed my issue in 10 minutes.

New sensor … same issue. Gauge was good until hot and at idle. Any additional thoughts? Engine runs smooth when gauge bottoms out.

 

[Leebo24]

New sensor … same issue. Gauge was good until hot and at idle. Any additional thoughts? Engine runs smooth when gauge bottoms out.

Very odd that this only started to happen after valve cover gasket replacement.

 

[ChasUGC]

Yeah, I'm trying to diagnose a similar problem. I replaced a faulty oil pump sensor a while ago, and I returned it, because it was also faulty and got a new one. When my Jeep is cold, it makes a lot of lifter noise. I'm attributing this to the last oil change, so I'm giving my mechanic the oil and filter that I want on it. High Mileage Synthetic Blend and a good anti-drain back valve oil filter. I didn't have that problem before the oil change unless my oil level got a little low. But, if I drive on the highway and the Jeep gets a good workout, on a very hot day, the oil level will bottom out after I get off the freeway and come to a stop. I will get warning lights for the low oil pressure. But, not always. No engine noise or anything, and when I drive again the oil pressure goes up a bit. But, this worries me, with all the cold noise issues, and the freeway situation. My engine has 215,000 miles on it, so I want to take care of it. It is soundless when it warms up to temperature. My mechanic thinks it is just an old engine, but i want to squeeze all the miles that I can out of it, until it has to be replaced. I don't relish having to spend $2000-$3500 dollars for a new engine. I'm leaning towards a new oil pump and sensor if the issue continues. This Jeep is such a drain on my pocketbook.

 

[Leebo24]

I have zero engine noise or roughness when the gauge zeros out. I agree with you …. Extremely frustrating and not fun on the wallet.

 

[MikeE024]

Just ordered Mopar sensor from Rock Auto. Will change and post results.

Good call

Installing a new Mopar oil pressure sender solved my issue when the same thing happened to me on a hot day.

Best of luck.

 

[MikeE024]

Yeah, I'm trying to diagnose a similar problem. I replaced a faulty oil pump sensor a while ago, and I returned it, because it was also faulty and got a new one. When my Jeep is cold, it makes a lot of lifter noise. I'm attributing this to the last oil change, so I'm giving my mechanic the oil and filter that I want on it. High Mileage Synthetic Blend and a good anti-drain back valve oil filter. I didn't have that problem before the oil change unless my oil level got a little low. But, if I drive on the highway and the Jeep gets a good workout, on a very hot day, the oil level will bottom out after I get off the freeway and come to a stop. I will get warning lights for the low oil pressure. But, not always. No engine noise or anything, and when I drive again the oil pressure goes up a bit. But, this worries me, with all the cold noise issues, and the freeway situation. My engine has 215,000 miles on it, so I want to take care of it. It is soundless when it warms up to temperature. My mechanic thinks it is just an old engine, but i want to squeeze all the miles that I can out of it, until it has to be replaced. I don't relish having to spend $2000-$3500 dollars for a new engine. I'm leaning towards a new oil pump and sensor if the issue continues. This Jeep is such a drain on my pocketbook.

I had what seems like a Christmas tree’s worth of lights come on the dash when my oil sender acted up. The engine rough idled and then worked normal again as if it never happened after I shut off the engine and restarted it a few minutes later. A new Mopar sender solved the issue for me.

I had good luck with Valvoline synthetic blend and full synthetic using a Wix xp, mopar, and mobil filter.

Many of us have lifter noise and don’t need a rebuild. Some guys have had lifter noise for many thousands of miles and their tractor engine just keeps on doing what it does.

I had good luck with removing lifter tick (only happened on startups for me) by adding MMO (marvel mystery oil) in with my oil.

I’m too afraid to run MMO with the turbo so I’m running Redline now days for different reasons.

 

[Leebo24]

Good call

Installing a new Mopar oil pressure sender solved my issue when the same thing happened to me on a hot day.

Best of luck.

Appreciate the reply. Didn’t fox my issue. Same thing happened. Motor got hot, and at idle, gauge went to zero.

 

[MikeE024]

Appreciate the reply. Didn’t fox my issue. Same thing happened. Motor got hot, and at idle, gauge went to zero.

I hate to ask, but are you sure it’s a Mopar sensor?

Assuming it is, I’d check for codes and then check wiring. Make sure the grounds are all hooked up, and that the harness wires are in good shape specially around the rear-most of the valve cover (driver side).

Another thing to consider is cleaning and reseating the plug to the oil sender and your PCM plugs. Just give everything the best look through that you can. If the sender plug has junk on the pins, you could have high
resistance where the pins meet. Or maybe something isn’t fully connected properly and once hot, they expand and stop making a proper convection.

Don’t forget to look for bent or pushed pins when inspecting/cleaning plugs with connector cleaner and/or Deoxit.

I’d also check your oil level and make sure all is good there. While not impossible, it seems odd that the oil pump would temporarily give up the ghost (only when hot) after other work was done.

Just to be sure, I’d check wires, grounds, and connectors (ensure they are clean and tight).

Sadly, a mechanic jacked up my last rig leaving me stranded up the road due to to damaging wires near the back of the valve cover. Not saying your mechanic did anything wrong, but things happen especially in the hands of “professionals”.

 

[Leebo24]

I had what seems like a Christmas tree’s worth of lights come on the dash when my oil sender acted up. The engine rough idled and then worked normal again as if it never happened after I shut off the engine and restarted it a few minutes later. A new Mopar sender solved the issue for me.

I had good luck with Valvoline synthetic blend and full synthetic using a Wix xp, mopar, and mobil filter.

Many of us have lifter noise and don’t need a rebuild. Some guys have had lifter noise for many thousands of miles and their tractor engine just keeps on doing what it does.

I had good luck with removing lifter tick (only happened on startups for me) by adding MMO (marvel mystery oil) in with my oil.

I’m too afraid to run MMO with the turbo so I’m running Redline now days for different reasons.

This is all great info! Thank you. It is a Mopar sensor. Very frustrating to have these issues just after taking it to a shop. I will check wiring and connections. Hope it’s something simple.