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bigdee 01-11-2012 08:06 PM

low oil pressure
 
Hi to all. I am new to this forum and hope to tap into some expertise and experience. Problem: 4.0 2004 Cherokee runs great, very quiet and runs strong but after it warms up the oil pressure drops enough to trigger the "check Gage" light. Is it possible for the 4.0 to have worn bearing clearance and still be so quiet? I am running 15w-40 fleet oil and mopar filter. If it was noisy I wouldn't hesitate to pull the oil pan and check things but I would rather wait till warmer weather. Do you think I am taking a risk by waiting a couple of months? This is a daily driver @ about 200 miles a week. I checked with a mechanical gage and at operating temperature the pressure was 45 at 2500 rpm but fell to 8 at idle(650)

2005JGC 01-12-2012 01:33 AM

Re: low oil pressure
 
my first suggestion with ANY oil pressure light is to hook up a mechanical gauge and see what your at.

bigdee 01-12-2012 01:34 PM

Re: low oil pressure
 
Quote:

Originally Posted by 2005JGC (Post 550976)
my first suggestion with ANY oil pressure light is to hook up a mechanical gauge and see what your at.

Done that....6-10 lbs at hot idle. No water in oil. Looked in oil fill cap hole and oil is circulating. I hear a VERY faint knock but it sounds more like piston slap.....runs strong and uses no oil. I have 95 k on odometer but I am not sure if this motor is original because the build date doesn't match the body build date.
The motor # is 009MX27 and under that number is a laser etching that looks like this; CCCCCCC??. Any help would be appreciated.

2005JGC 01-12-2012 04:10 PM

Re: low oil pressure
 
The fact that it is happening warm once the oil has thinned out, and that is in fact below spec (which is already absurd at a measly 13psi but comfortably 3 times that on a healthy motor). I would do an oil change and capture some of the oil and shine a flashlight through it to inspect for metal debris. if you see some metal drop the pan and pop your connecting rod caps and your main bearings too (not all at the same time of course). If you don't have a torque wrench to re-install them don't do this.

bigdee 01-12-2012 05:11 PM

Re: low oil pressure
 
Quote:

Originally Posted by 2005JGC (Post 551331)
The fact that it is happening warm once the oil has thinned out, and that is in fact below spec (which is already absurd at a measly 13psi but comfortably 3 times that on a healthy motor). I would do an oil change and capture some of the oil and shine a flashlight through it to inspect for metal debris. if you see some metal drop the pan and pop your connecting rod caps and your main bearings too (not all at the same time of course). If you don't have a torque wrench to re-install them don't do this.

Thanx for the reply. I did check for metal and found some VERY fine shiny stuff....drug a magnet through oil and it came up clean so I assume the few flakes were bearing material. I have a suspicion that this motor may have had the infamous head crack at one time because when I shine a flashlight inside the valve cover everything looks brand new. The cast iron is a shiny grey color. I would think that after 95k miles it would have a brown buildup. If the coolant did get into the oil at one time would the cam bearings fair worst? Would excessive main or rod clearances cause low oil pressure without knocking?
If the cam bearings are shot but the bottom end is good how long would this engine last?

2005JGC 01-13-2012 12:42 AM

Re: low oil pressure
 
All I can say is wherever your wear is, with you low on pressure your grasping at straws now... I would love to say it will run forever like this (as most 4.0l knocking and ticking is concerned) but if you have a worn bearing that is causing low oil pressure there is only so much time before that bearing gets worse and the low oil pressure wipes others out.

2005JGC 01-16-2012 07:22 PM

Re: low oil pressure
 
I just dealt with a low oil pressure in a 4L on Saturday... it was low on my mechanical gauge, that was when I came across a star case regarding cam bearings walking out of their journal and causing low oil pressure. Ultimately this didn't soften the blow of the required repair (not that I said this IS what was happening, I needed to tear it down) The repair was "short block" added in with the missing coolant and presumed cracked head (again further tear down was required) We were looking towards a long block. The problem is an enlarged bore so just installing a new bearing your going to end up in the same place.

Fernando07 01-19-2014 07:42 PM

Re: low oil pressure
 
What must be proper motor oil (psi) for Grand Cherokee 2014, thanks.

hoffmanestates 01-20-2014 06:22 AM

if your going to keep this beautiful truck, I wouldn't drive it anymore, granted I know 0 about these I6 but just had a semi built lower end grenade on a fellow members wrx as he just had it rebuilt, due to internal complications. shortly after bearing #4-#3 grenaded due to oil starvation. unfortunately now at this point he needs new Bock halves as they are not repairable at this point. will this happen doubt it but never know.

saldiafoster 02-26-2014 11:45 PM

Re: low oil pressure
 
I bought a 2011 Jeep Grand Cherokee 1 month ago and each morning upon start up the Oil Pressure Light comes on at idle. However, when I start driving it comes off. Took it to the dealer's service center FOUR (4) times I was told they are not seeing any light. Last time it was there for 2 weeks - they told me they did not see any light, however the next morning upon start up i see the light again :eek:
Can someone please assist me on what to do.

Thank You.
Saldia

lstowell 02-27-2014 01:49 PM

Re: low oil pressure
 
Which engine?

Could be drain down or bad sensor. The sensors are infamous for failing, but are quite easy to change.

When you take it to the dealer, do you leave it overnight and ask them to check it first thing in the morning?

Do you know the service history of your engine?
Does it burn oil?

What oil type and weight are you using?

Have you tried Seafoam treatment followed by a good oil with 10-50 or 20-50 rating, and possibly a can of STP?

saldiafoster 02-27-2014 05:30 PM

Re: low oil pressure
 
Hi Istowell,

Thank You for responding.

I have a 5.7 V8 engine.

The dealer had it for 2 full wekks driving it as well as checking it upon start up in the mornings. As per mechanic and service manager they did not see any light even after i sent them pictures of it.

I am not aware of the service history nor if it burns oil.
I don't ebe know what type or weight oil it use.

I think because I am a woman they are taking advantge of the situation as I refuse to believe they had it for 2 weeks and did not see this "oil pressure" light yet the next morning after I picked it up I saw the light when I start the vehicle and it sat in Idle for less than 5 minutes.

I have being going back and forth with htese people for the last month and I still have the same issue.

At one point the guy told me he change the oil pressure switch, so i shouldn't be seeing the light however the next morning i woke up and start the vehicle the light came back.

I am upset to the point that I fell in love with jeep now I hate it.:mad:


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