Oil pressure dropping to 0 at idle on XJ

[activeshooter1]

depending on your lift it may involve just about dropping the axle, the shallow end near the front of the engine needs room to clear the pickup, you can get it off pretty easy by dropping the pan enough to get to the two bolts that hold the pump on. for reinstaling you need the room. the pan bolts that are around the exaust can be a real pain.
eta been there, if this don't work find a donor motor cause the cam bearing are most likely toast and its cheaper to do a swap than rebuild

 

[ScienceguyXJ]

Anyone ever seen an article with pics on how to check the main and rod bearings? I've never done it before. Think I'm going to opt for a regular pump and not a high volume one so that way if the problem persists I'll know for sure the bearings are shot.

 

[JJacobs]

Checking bearings is a three step process. Step one, remove bearing cap and bearing insert. It should be a light color, very minor scratches or imbedded specks are ok. A copper color is not, that indicates you're down almost to the base layer of the bearing insert. If it looks ok and you want to be sure, on to step 2: Plastigauge. This is available at basically all parts stores, you want the .001-.003 variety. It is a thin strip of plastic like material. Cut it just shorter than the width of the bearing, clean the surfaces, lay it on the crank. Install the cap and torque to spec. Do not rotate the crankshaft at this point, obviously, it will distort the plastigauge material. Now remove the cap and use the width gauge on the packaging to determine the actual bearing clearance. Compare to spec. If ok, reassemble, if not replace bearings and further evaluate whether crankshaft will need to be polished or resurfaced.

Step 3 is of course reassemble and retorque. Should have mentioned above, take note when the bearing caps come off.. there is a tang in the bearing insert, it only fits in the cap one way. Also note that the main bearing caps fit snugly down into the block, it is common for them to need a light tap to dislodge even with the bolts out. Conversely, they will probably need to be tapped down into the block before the bolts are run down or you might screw up the bearing caps if you just crank the bolts down.

Cam bearings aren't so easily checked. The only way you'll know if they're hammered with the cam still installed is metal coming out the side of the bearing. That's rare, though; cam bearings usually outlast all the others.

 

[orange]

oil sample to run Oil Analysis on old oil ??? (if some miles on it.)

Shot bearings would really show up!

also clue on grade of oil in it now.

 

[ScienceguyXJ]

Thanks, found a pdf of the service manual also, that should do it!

 

[ScienceguyXJ]

Well started tearing into the thing tonight. Didn't get my oil pan off cuz my jack crapped out on me trying to lift the body a little, so I switched to pulling off the valve cover. Noticed the coolant overflow was drained again after having had the coolant flushed on Sat. and it looked like the coolant was kind of darker than it should be in the radiator. Noticed a lot of vapor coming out of the oil as I drained it... got the cover off and there was all kind of milky gunk all over the inside of the cover and think I saw some green antifreeze near what looked like a hairline crack between 3 and 4! Time to rebuild!!!

 

[gradon]

Oh, the 0331 :doh:

 

[ScienceguyXJ]

Whoever designed that thing should be dragged out into the street and shot

 

[ScienceguyXJ]

Put the oil pan back on tonight and started her up with the valve cover off and sure as sh*t she started steaming and I could see antifreeze running with the oil on the head...

 

[ScienceguyXJ]

Anyone know what it takes to switch from a 0331 to a 0630 or 7120 head. From what I can find it sounds like you just need to modify something to mount up the coil ignition rail to the new head... Thinking about having a shop in town build me a 4.6L stroker!

 

[gradon]

You can use either the 7120 or 0630--just figure a way to secure the coil rail(I've read of erector style straps). The 7120s and early 0630s will have a port for the coolant temp sender for the dash gauge on the ds rear corner of head, so leave the sensor in and unplugged if you choose one of those. Also, the exhaust ports will be larger than the stock 2000+2001 split exhaust manifolds, so you'll want to use a header for a 91-99 4.0(except one for the 99 WJ and TJ that got the 0331 a year ahead of the XJ).

 

[joe_peters]

You can also get the later 4.0 head with "TUPY" cast into it as that was the "fixed" casting.

 

[ScienceguyXJ]

TUPY??? They supposedly fixed the 0331 head so it wouldn't crack later on?

 

[joe_peters]

TUPY??? They supposedly fixed the 0331 head so it wouldn't crack later on?

That is the info posted on this and other forums. Search "TUPY" and you will get about 15 threads discussing the 0331 and TUPY casting.