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4.0 Drops Oil Pressure when at idle.

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Discussion starter · #1 ·
Hey I'm new and this is my first post. I found your site when looking for answers to my problem on google.com. Ok to my point. I have a 2001 Jeep Grand Cherokee Laredo with a 4.0L I6 and it has about 120k on it. today while at a stop light the oil gauge dropped to "0":nono: and my "Check Gauge" came on. When the light turned green and I started going again the Oil Gauge went back up to about 40-50 PSI. but when ever I stopped it would drop back down. So I went to Auto Zone and got a new sending Unit hoping this would fix it. But it didn't. Once it warmed up and I was sitting at a light it would drop back down to about 20 PSI it's never done that before. it's not knocking or ticking, I'm using a FRAM ph-16 oil filter and Mobil 1 10w-30. I'm freaked cause it's the only Thing I have to get me to and from work and I’m pretty broke. Any help on how I can fix it would be great.
Thanx

David.
 
#2 ·
Welcome to the forum. Thanks for filling out your Jeep info and being very descriptive of your problem. As a general point, I'd say you'll probably want to steer clear of the fram oil filters, except for maybe the tough guard. For your oil pressure problem, do you notice any change in the way the engine feels while it's idling and the pressure gauge drops? I'm not entirely convinced that the gauge isn't failing or you don't have more of a wiring issue if you don't feel any difference in the Jeep. With no oil pressure, I would think the Jeep should stall or at best run very rough. If the pressure is verified to be dropping, my best guess would be that the pump is going bad.
 
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#4 ·
This might be comforting.. my 2001 Dodge Ram has your exact symptoms. The compression is fine though. Just every now & then it will go crazy. It did it for about a week & I checked the compression and it was perfect. Now it only does it once in a blue moon. If it was my Jeep I would have fixed it already but I know I have nothing to worry about.
 
#5 ·
strange, especially if it doesn't have poor running symptoms...

do these guages often act up? is it not uncommon to have an oil pump/sending unit fail with such low mileage?

I notice my needle too, but my guage is in BAR... It often hangs around 3 BAR (close to 44psi?) and gets a wee bit higher with the revs up, we bit lower in the revs down. I have an I6 as well, and avoid the fram filters - although I still use dino oil.

I don't know jeeps very well, but in some cases I would open the oil cap while the engine is running to see that I'm getting oil up top, not sure if that's a good idea or not though.
 
#6 ·
try a mopar sending unit, for some reason Jeeps do not like many aftermarket sending units for any of its sensors. you also might get a loaner mechanical pressure gauge from your local parts store and see what the pressure really is.
 
#7 ·
Definitely start with a mopar oil pressure sending unit... the aftermarket ones are crap.... of course, the mopar ones are crap too, but at least the read right for a while... LOL
 
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#8 ·
My buddy has the same issue with his XJ, every once in a while it does it but the engine is solid. He hasn't tried any fixes yet...at least that I know - haven't talked in a while.
 
Discussion starter · #9 ·
the88thpianoman said:
For your oil pressure problem, do you notice any change in the way the engine feels while it's idling and the pressure gauge drops? I'm not entirely convinced that the gauge isn't failing or you don't have more of a wiring issue if you don't feel any difference in the Jeep. With no oil pressure, I would think the Jeep should stall or at best run very rough. If the pressure is verified to be dropping, my best guess would be that the pump is going bad.
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It doesn't feel any diffrent when it drops. Not that I can hear or feel. I did use a MOPAR Sending Unit. My aunt is the Head person for the Parts Department over here and one of our dealer ships. I'm going to do a oil change today. any tips for the kind of oil I should use and filter?
 
#10 ·
DavidMoses said:
It doesn't feel any diffrent when it drops. Not that I can hear or feel. I did use a MOPAR Sending Unit. My aunt is the Head person for the Parts Department over here and one of our dealer ships. I'm going to do a oil change today. any tips for the kind of oil I should use and filter?
Click to expand...
Have you tried changing your oil?

Dodge, and Chrysler vehicles have an oil bell that sits too low to the oil pan, as your oil gets sludgey the oil pump sucks that crap up. Mine did it when I first got my jeep, changed the oil never happened again. I'd say thats probably your problem since jeep is unfortunately made by chrysler. :(

As a tip to everyone, always start with the simplest solution first. This for example, the oil is the cheapest solution. Change the oil, if it still continues then Hey! you got clean oil and a filter at least. I hear a lot of people that are like "Man I wasted a lot of money on putting parts on my car when all it was, was so-and-so." Well at least all those parts you just replaced won't need to be changed for a while. :D
 
#11 ·
This same thing happened to me when I first got my Jeep 01 WJ 4.0. Luckily it was still under warranty. I took it to Jeep as soon as I noticed the pressure dropping to 0 at idle. Jeep put in a new oil pump, but that didn't help so I took it back. The fix for me was a brand new long block luckily I didn't have to pay for it. My symptoms where the same, the jeep seemed to be running fine except for the low oil pressure.

I hope this is not the case for you.
 
Discussion starter · #12 ·
severrin said:
Have you tried changing your oil?

Dodge, and Chrysler vehicles have an oil bell that sits too low to the oil pan, as your oil gets sludgey the oil pump sucks that crap up. Mine did it when I first got my jeep, changed the oil never happened again. I'd say thats probably your problem since jeep is unfortunately made by chrysler. :(

As a tip to everyone, always start with the simplest solution first. This for example, the oil is the cheapest solution. Change the oil, if it still continues then Hey! you got clean oil and a filter at least. I hear a lot of people that are like "Man I wasted a lot of money on putting parts on my car when all it was, was so-and-so." Well at least all those parts you just replaced won't need to be changed for a while. :D
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Yup just did an oil change. Used a K&N oil filter and Mobil1 7500. It's still doing it but it only seems to do it when it's been driving for more then 25 mins. It starts up with at least 45-50PSI then after driving for a little bit it goes down to 40psi when at idle. then when it's really warmed up and been running it falls faster and faster to about 20psi to almost 12psi. that's when ever I take my foot off the gas. once i'm on the gas it goes back up to 45psi. So new oil Check, New Sending Unit Check. I'm thinking about taking it to someone else to see whats wrong but don't wanna get raped in the butt. I only have about 300 bucks to fix it.
 
#13 ·
DavidMoses said:
Yup just did an oil change. Used a K&N oil filter and Mobil1 7500. It's still doing it but it only seems to do it when it's been driving for more then 25 mins. It starts up with at least 45-50PSI then after driving for a little bit it goes down to 40psi when at idle. then when it's really warmed up and been running it falls faster and faster to about 20psi to almost 12psi. that's when ever I take my foot off the gas. once i'm on the gas it goes back up to 45psi. So new oil Check, New Sending Unit Check. I'm thinking about taking it to someone else to see whats wrong but don't wanna get raped in the butt. I only have about 300 bucks to fix it.
Click to expand...
Buy an oil pan gasket, and drain your oil into a container you can use to save it if you want. Take off your oil pan and check your pump bell housing, see if the screen is clogged and how much sludge is on the bottom of the pan. If it's clean, then your pump might need to be replaced.
 
#14 ·
What is the weight/viscosity of the oil you are using?
 
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#18 ·
DavidMoses said:
Okay so I looked at the Sending Unit again and in the wireing there is a **** load of oil in it. I tried to clean out as much as I can but really couldn't get the much out. And Tips
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some halogen free brake cleaner or electronics cleaner
 
#19 ·
DavidMoses said:
Okay so I looked at the Sending Unit again and in the wireing there is a **** load of oil in it. I tried to clean out as much as I can but really couldn't get the much out. And Tips
Click to expand...
The previous sending unit was broken, and oil was coming out through it into the connector.
Clean it carefully, and replace the sending unit with a new mopar one.
Get the correct socket at the auto parts store to tighten it.
 
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