Cracked cylinder heads, 2000-1 Cherokees
01-25-2018, 10:03 PM
#16
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Year: '98
Engine: 4.0 I6
Wouldn't you need a splitter to keep the factory sending unit plugged in? I assume the PCM is going to throw codes about reading zero oil pressure (missing factory sending unit)
01-25-2018, 10:15 PM
#18
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Year: 1995
Model: Cherokee(XJ)
Engine: I6 4.0L
Does the 00-01 throw low oil pressure codes?
If you're just testing, and you do get a code, you know what it is and can clear it, right?
If you're just testing, and you do get a code, you know what it is and can clear it, right?
01-25-2018, 10:23 PM
#19
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How long has it been drinking coolant?
Low oil pressure is going to be 5 psi and under at hot idle, verified with a mechanical gauge (remove the factory one an use a mechanical or digital standalone gauge for an exact measurement). If you have 10+ psi at hot idle (and I mean hot, like after a 30 minute drive minimum) then you should be in OK shape to just slap a new head on there. The dash gauge is not really that accurate in my experience
Changing the bearings is going to involve pulling the motor, and honestly I would rather build or source another used shortblock and swap if you want to go that route.
I unfortunately don't think most parts stores rent an oil pressure test kit. They have fuel pressure, cylinder pressure, etc but not for oil pressure IIRC
Here is a cheap kit that would do the trick
https://www.amazon.com/8milelake-Eng...ure+gauge+test
Low oil pressure is going to be 5 psi and under at hot idle, verified with a mechanical gauge (remove the factory one an use a mechanical or digital standalone gauge for an exact measurement). If you have 10+ psi at hot idle (and I mean hot, like after a 30 minute drive minimum) then you should be in OK shape to just slap a new head on there. The dash gauge is not really that accurate in my experience
Changing the bearings is going to involve pulling the motor, and honestly I would rather build or source another used shortblock and swap if you want to go that route.
I unfortunately don't think most parts stores rent an oil pressure test kit. They have fuel pressure, cylinder pressure, etc but not for oil pressure IIRC
Here is a cheap kit that would do the trick
https://www.amazon.com/8milelake-Eng...ure+gauge+test
25K miles of drinking coolant approximately. No milkshake in the valve cover or oil pan, so my suspicion is the head is cracked all the way through. My mom bit the bullet today and ordered the Clearwater 0331 head. My dad is a 40 year veteran heavy duty mechanic, and suggests that it is possible to do the main bearings by pulling the oil pan once the head is off, whereas the cam bearings are not possible due to needing to retain the lifters whilst sliding the cam out. So that is the most likely amount of work that will be performed, hopefully the engine won't die. I will make a new thread about the procedure (being performed by a certified mechanic) and update it on how the engine is performing periodically.
01-25-2018, 10:32 PM
#20
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Engine: 4.0 I6
Do it. And worst case down the line, you can swap the head on another block and throw it back in the Jeep.
That's what I would do.
That's what I would do.
01-25-2018, 10:41 PM
#21
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Year: 2000
Model: Cherokee(XJ)
Engine: Golen 4.6L
Oil pressure wasn't included in the OBDII spec. Although OBDII has troubleshooting value, the requirement that cars have OBDII came from the California Air Resources Board and the EPA. In other words, it was all about emissions. A misfire or bad O2 sensor was considered an emissions issue; low oil pressure wasn't.
01-25-2018, 10:46 PM
#22
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And hopefully you dont get the same surprise I did when the head comes off. Wasted cylinder walls but the bearings were ok. The PO of mine had the head gasket replaced but did nothing about the crack in the head. Sound familiar? Well I dont know how long he drove it for but it wasted 5 of the cylinder walls. 25k miles sounds like a ton with coolant leaking internally. I hope for the best for you but just know there is the possibility of the worst like what happened to me.
01-25-2018, 10:52 PM
#23
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Year: '98
Engine: 4.0 I6
Yeah, 25k miles is a lot.
But I assume you would see it when changing the oil if it was ingesting much.
OP, post some pics of the valves and cylinders. And the crank bearings if you guys change those
But I assume you would see it when changing the oil if it was ingesting much.
OP, post some pics of the valves and cylinders. And the crank bearings if you guys change those
01-26-2018, 12:19 AM
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Not sure if the mechanic has a cellular phone with a decent camera or a digital camera, but I will certainly try to get photos for the purposes of these forums 
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