2000 Jeep Wrangler Low oil pressure, zero oil pressure at I

WANTJEEPWORKNOW

MEMBER
2000 JEEP WRANGLER
6 CYL
4WD
AUTOMATIC
131,000 MILES

I have a 2000 Jeep Wrangler Sahara with 4.0 L inline 6, about 130,000 miles on it. When starting the jeep when cold the oil pressure reads 40. When going for a while it reads a little above 20 on the freeway and around 10 in town. At an idle, like when stopping at an intersection, it goes to zero. The check guages light comes on when it gets to zero. Once I get going again the oil pressure goes back up from zero. There is no noise or vibration. The vehicle has not lost a drop of oil since I noticed the problem. I have also had to put lots of coolant in the radiator since it is often running low, but I cannot find an external leak and am 99% sure there is not one. I am reasonbly sure that water is not getting into the oil. The temperature never goes over the midpoint on the guage and I have driven it over extended distances. I do not know if the problems are connected or not. When noticing the oil pressure dropping to zero, the first thing I did was changed the oil pressure sensor. When that proved not to be the problem I sought the help of a mechanic that thought it best to change the oil pump. So I did that, but there was absolutely no change. I had a mechanic connect an external oil guage up in place of the sensor and his guage confirms zero oil pressure at an idle. I am at a complete loss and in need of help.

6 Replies

CJ MEDEVAC

MECHANIC
11,005 POSTS

See my profile, I do not know your rig, for I am a CJ guy......I hurt for you, cause I know the deal when you think your Baby is having Bad Problems.

You need a Chilton or Haynes Manual to guide you.

I have rebuilt and helped rebuild many engines in the past, mostly Jeep 258, some 304s and a few Ford truck engines, By no means am I an Expert.

I will go ahead and hit you with worst case, so that the rest may be HOPE!

Your engine may be SLAP WORE OUT. Large clearances in bearing, wear on major components, like the Crankshaft, Poor maintence may have helped it along....Done with worst.

What about a WEAK SPRING...etc. In your OIL PRESSURE RELIEF VALVE ASSEMBLY? On CJs its above the Oil Filter. See your New Manual!

What about using "LUCAS" oil stabilizer, instead of 1qt. oil?

The oil pump you installed, was it standard, or can you get a High Volume for it, such as in CJs?

Thats about all I got, I will keep thinking.

Reply,

Love, Turddog

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Tuesday, April 13th, 2010 AT 8:31 PM

DWTURNER45

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Your description of the problems you are having match mine exactly, only I have 73,000 miles on mine, right down to the point on adding coolant to the reserve tank. The problem with loosing coolant has been going on for a while, took it both to my mechanic and the Jeep dealer with no resolution. The issue with the oil pressure just started in the last couple of days. I really hope someone has a answer to this!

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Tuesday, April 20th, 2010 AT 8:06 AM

WANTJEEPWORKNOW

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4 POSTS

Let me know if you find the answer and I will do likewise. With only 73,000 yours gives me hope that it is something simple and not something like a previous owner having grossly overheated/abused it and wearing out bearings etc. Irritating that the dealership has no clue isn't it?- I talked with one too with no result.

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Tuesday, April 20th, 2010 AT 7:33 PM

MHPAUTOS

MECHANIC
31,937 POSTS

HI there,

Thank you for the donation,

With no oil pressure indicated at the external pressure gauge fitted would indicate a number of things,

1. No oil in system.
2. Blocked pick up.
3. Cracked pick up tube.
4. Defective oil pump or drive.
5. Faulty (stuck open pressure relief valve)
6. Faulty oil filter.
7. Blocked oil gallery.
8. No prime in pump due to air.

Often new pumps need priming or they will not pick up oil. Even with excessive bearing clearances you would still get some pressure, I feel that this will be a pump or blockage issue.

Mark (mhpautos)

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Tuesday, April 20th, 2010 AT 7:48 PM

WANTJEEPWORKNOW

MEMBER
4 POSTS

I took the cover off the engine to see if oil was in fact getting to the lifters at 0 pressure on the gauge. I waited until the temperature rose and the pressure reading dropped to 0 and the "check guages" light came on. Everything looked to be the same as it was when the engine temp was 0 and the pressure read 40. I then used a paper towel to dry up one of the lifters while the engine was running and waited to see if it took very long to fill. It took only seconds to fill back up. It would seem that oil is being pumped from the pan to the top of the engine, no problem at any temp, so it must be after that point that the loss in pressure occurs? Here are a couple pics to show the oil level in the lifters. I think this level is normal.

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Sunday, April 25th, 2010 AT 11:26 PM

CJ MEDEVAC

MECHANIC
11,005 POSTS

Well boss, the Aussie, threw in a factor I never thought of, the Pick-up, sucking air thru a crack or bad gasket or seal. HE ALSO GAVE ANOTHER VOTE TOWARD THE OIL PRESSURE RELIEF---They can get messed up, my Pap's Ford F-150s Got stuck CLOSED, We blew off 4 filters (leaving the screw-on part, on the engine) Then we figuered out what was going on!

I have thought about this, and talked to the local production engine rebuilder, he says it only takes 4 lbs of oil pressure to keep an engine safe, but he also said, he didn't want to experience it!

I have a '46 Willys (my avatar) It originally had a "Old Tractor" type filter on it, when I rebuilt him (a strong masculine pronoun) I changed to a remote, spin on filter. (The original was remote also, but it used the little "bucket handle" filters)

"Willy" does not filter oil, as it comes thru the pump (100% filtered oil) He sorta filters off of the oil galley (throwing #s, about 10% as the engine runs)

If I were to stick on a REGULAR filter, all of my Oil Pressure would dissapate thru the wide open filter.

1st Point--maybe a plug in/on a galley loose/fell out/crack in the galley

I have to run a PB 50 agriculture, spin on filter, to restrict oil flow thru the filter (when you, look in the threaded hole, there is a 1/16-1/8 inch hole, to slow the flow) Way, way back, some cars didn't even have filters, so robbing and filtering from the galley was a foward step up!

2nd point---Have you changed the filter--maybe it is stopped up or MFGed wrong

Your lifters operate off of a main galley, I do not know your engines OIL FLOW CHART, But a real good guess is your pressure gauge is taking its Sample---Way before it gets to the galley with the lifters.

3rd point----with nothing to lose, at this point, Loosen your filter slightly, wait for the ZERO reading----THEN spin her loose a little, see what kind of MASSIVE SQUIRTAGE Occurs----I always use my Brother-In-Law for these type "NELSOMATIC TESTS"

This may narrow it down to before or/ after the filter/ oil pump (or do 2 tests, 1 with pressure, 1without)

As for the water loss, I will ask, My friend ED, owner of the "Engine Exchange" again.

Anybodys Thoughts?

Love, Turddog

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Monday, April 26th, 2010 AT 2:05 AM