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Author Topic: 2000-2001 Jeep Grand Cherokee - No oil pressure at idle  (Read 5916 times)

Offline aka_chewy

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2000-2001 Jeep Grand Cherokee - No oil pressure at idle
« on: May 04, 2010, 10:04:04 pm »
My mom just called me because they took their 2000-2001 (she couldn't remember) jeep (pretty sure it's the 4.0) into the mechanic because they just started noticing the oil pressure gauge read 0 when they would come to a light or stop sign.  When they started driving, the pressure came up and it was fine. 

Well, their mechanic told them the whole motor needed to be replaced and that this was a notorious issue for the jeeps.  Now, that doesn't seem to make sense to me, but I wanted to get other's opinions and if anyone has heard of this. 

I"m off to the google to see what I find, but trust everyone's expertise here over google links.

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Re: 2000-2001 Jeep Grand Cherokee - No oil pressure at idle
« Reply #1 on: May 04, 2010, 10:22:07 pm »
Sooooooo, without tearing the motor down or looking at anything, he determined the motor needed to be replaced?......

:scratch:

Offline aka_chewy

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Re: 2000-2001 Jeep Grand Cherokee - No oil pressure at idle
« Reply #2 on: May 04, 2010, 10:24:35 pm »
That's what I gathered.  I was going to call the place to talk to them, but they were closed for the day already.  I'm going to get more info tomorrow, but was curious if other's have heard of this issue.

Offline batman13

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Re: 2000-2001 Jeep Grand Cherokee - No oil pressure at idle
« Reply #3 on: May 05, 2010, 12:29:33 am »
ok, i have the same motor in mine (short 2 cylinders)
occasionally i have the oil pressure drop to 0 when i stop at a light, when the idle drops below a certain point, i think its like 800rpms. im gonna go out on a limb and say if the oil pump isnt faulty theres something making the jeep idle too low

it aint low till it scars asphalt

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Offline aka_chewy

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Re: 2000-2001 Jeep Grand Cherokee - No oil pressure at idle
« Reply #4 on: May 05, 2010, 12:44:59 am »
That's an interesting thought bat...I'll have to check that out.  I know I posted with out a ton of info, but I was to antsy to wait until tomorrow to ask.  And I wanted to have some intelligent questions when I call them. 

Offline batman13

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Re: 2000-2001 Jeep Grand Cherokee - No oil pressure at idle
« Reply #5 on: May 05, 2010, 12:52:31 am »
part of me also wants to say it could be the idea that the oil pressure sensor is either faulty or, it dosnt read below a certain pressure so it just goes to 0

it aint low till it scars asphalt

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Offline kenz

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Re: 2000-2001 Jeep Grand Cherokee - No oil pressure at idle
« Reply #6 on: May 05, 2010, 03:36:03 am »
I'm gonna agree with bat. I had a '91 S-10 4 cyl. that did the same thing, and it was the pressure sending unit. Went threw 4 of them.  :argh: Anyway, if it was me, I'd be finding a different mechanic pronto.


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Offline Jr. Mechanic

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Re: 2000-2001 Jeep Grand Cherokee - No oil pressure at idle
« Reply #7 on: May 05, 2010, 04:49:53 am »
The mechanic is full of crap.  If the pressure was dropping to zero, that 4.0 would be knocking so loud your mother would have freaked.

As said above, the sending units are notorious for failing.  This is probably the 10th post I've seen in a week regarding this problem. 

I've heard a lot of bad things about aftermarket sending units, specifically for every good one you get a defective one.  Hit up Dave and I'm sure he can hook you up with a Mopar sending unit.

Oh yeah, the only major issues with the WJ model 4.0 were the head castings are notorious for cracking and the #4 piston skirts tend to break off for some reason.  The oil pumps are tough as nails.
« Last Edit: May 05, 2010, 04:51:28 am by Jr. Mechanic »

Offline Kilch123

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Re: 2000-2001 Jeep Grand Cherokee - No oil pressure at idle
« Reply #8 on: May 08, 2010, 04:25:55 am »
Any mechanic with any idea of what he's doing would put a mechanical gauge on it to verify the idle oil pressure

if the mechanical gauge also reads 0 at low idle, then there could be several issues:

Stuck open oil pressure relief valve
Worn camshaft bearings
Worn out oil pump

none of these are very likely though

I'd expect a sender or gauge problem...
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