Hello All,

Brand new, here.

I have a 200 Jeep Grand Cherokee Laredo 175,000 miles. For the last couple months I have had low engine pressure when I am decelerating or at idle (but shoots back up to normal when I accelerate).

I replaced the sending unit. Nothing.

I took it to a shop and they hooked up a manual gauge. They said it was running under the jeep specs. The number was below 10.

They are telling me either the Oil Pump is bad or my engine is on the way out. The mech. went on to say that it was most likely the engine on the way out.

Like I said, I have had this problem for a few months now and have not experienced any other issues -- i.e. sounds, loss of power, or choking.

I'm hoping to get some feedback of what you all thought of the my situation.

Thanks in advance!

 

Welcome to CF!

I'm thinking worn oil pump because of regaining pressure when the rpm's come up. I'm guessing this is a 4.0, right? It's pretty easy to replace an oil pump on them and they are known to wear out. Do the easy things first, then go on from there.

If it's a 4.7, good luck.

 

Thanks, dave1123, for your response.

It is a 4.0 engine.

Ok, so, because of the regaining of pressure upon acceleration you're thinking it's just a oil pump issue? On scale of 1-10, how sure are you that is the culprit?

 

I can't scale it. It's just an easy place to start. Once you have the pan off, you can Plastigauge the crankshaft bearings to know for sure. Take the pump apart and if it's worn, you should see grooves in the rotors and case. The clearance between the inner and outer rotors is where you loose the pressure.

 

Didn't the Grand Cherokee 4.0L get the 0331 head in 2000? If you have the 0331 head crack, that could also cause low oil pressure if the cam bearings are damaged. Have you had any cooling system issues or disappearing coolant?

 

Don't add problems where they aren't. He never mentioned overheating or coolant loss. I have 2 friends with XJ's that lost oil pressure because of worn oil pumps and were fine after replacing them. MY 2000 4.0 head cracked but I've still got 40 psi at idle hot and 45-50 cold. 188K miles as well. Usually these heads crack around 125-150K or so. He said this problem came on just recently, so I'm assuming oil pump.

BTW, the XJ's got the same head.

 

I know. I have an XJ that lost an engine to a cracked 0331.

I'm not trying to pile on problems, but he seemed to be latching onto the oil pump as his issue without ruling out other possible causes that are relatively easy to test for. If he didn't know about the 0331 problem, he wouldn't necessarily associate cooling issues with low oil pressure and might not mention them (which is why I asked that question, to get more information before offering a solution blindly). While the oil pump could be the culprit, it would be silly to replace it on a hunch and then find out that the money and effort was wasted on an engine that needs an overhaul.

 

Point well taken. I guess I'm too well acquainted with jeeps and their problems to think "out of the box" so to speak. My head cracked into an exhaust port creating lots of steam and coolant dripping out of the tailpipe. The ones that crack under the valve cover can leak into the oil for awhile and not be so obvious. My bad! I jumped on the oil pump because it was just last week that one of my friend's oil pump failed. He had it changed overnight.

SO....backing up a bit, are you loosing coolant out of the reservoir rapidly? Is there coolant on your oil dipstick? You can check your oil by pulling the drain plug when it's cold and just seeing what comes out in the first bit. You don't have to drain the whole crankcase, just a little bit. After it cools, the coolant will settle to the bottom and come out first. Also, take the oil filler cap off and look down the hole with a strong light. The crack will be right under the hole in most cases, right between the #3 and #4 exhaust valves. I will appear as a line of green or white stain.

Coolant ruins bearings rapidly and can cause a loss of oil pressure. I hope this is not the case with your jeep.

 

First lets put things in perspective:
1. 175,000 miles
2. low pressure at idle
3. normal pressure at highway speed

Low oil pressure at idle on a high mileage engine is not unusual and may not be a concern. As long as engine is not making noise and lifters are staying pumped up....you have adequate lubrication.
Do a google search on "low oil pressure 2000-2001 4.0 jeep engines". You will find this to be a common problem. Many people have thrown away money trying to fix it to no avail. IMO just keep a watchful eye and ear on things and if things get worse it will be time to react. If it makes you feel better my 2000 has had less pressure (4psi) for over 5 years and is still running like a sewing machine.

 

Check your oil daily, might have a leak.

 

What brand oil filter are you using? If it's a FRAM it may be the problem.

 

Hey folks,

I'm experiencing a similar symptom in my 4.7 2000 grand cherokee 160,000 miles. Appeared about 3 months ago when a chime came on when the engine was warm and at an idle. Oil pressure had dropped to nothing. anything over 1000 RPM's would bring it back to 40 psi(per dash guage) This has been pretty consistent for the time of a month and it went away.(no oil was changed in this time) I started to see 40psi at idle and a little higher at operating rpm's(1000 or more) the problem has since come back. every once in a while, it will just return to normal operating pressure for a short amount of time, then return to the low pressure issues. One big thing i have noticed is creamy looking oil around this oil fill when i look down the port. it is in the cap and down the neck to the crank case. I'm assuming that this is coolant in my oil... any thoughts?

 

The crud you're seeing in the oil fill is from condensation, pretty normal if you drive short trips. The oil pressure issue sounds like a failing sending unit. Replace it with a Mopar sending unit.