Is the potential for the 0331 cylinder head cracking a reason to NOT buy a clean and otherwise good looking 00 or 01? What are we talking here in terms of:

1. Likelihood of cracking.
2. Cost of replacement.
3. Difficulty (experience level needed) to replace.

From a newbie perspective, I'm seeing a lot of clean 00-01's, but im avoiding them due to being freaked out by this cylinder head talk.

 

I avoided them and got a clean 99 with the 0630. That's just one thing I don't have to worry about.

As for likelihood of it cracking there are polls out there that, even with a small sample size, the number of cracked 2000 0331 heads is significant. %80+ if I remember correctly. That tells me it's only a matter of time before you run into a problem and chances are the people who made it into high mileage without a problem are maintaining their coolant system very very well. Or they're just lucky.

I believe something changed not far into 2001 and the issue was perhaps remedied.. someone else can comment on this. A lot less 2001s have had the problem the 2000s did.

 

I had the head crack. Ran a solid year that way without realizing it. Had in in the shop many times and they all missed it. Ended up having a cracked head and cracked block. Still drove perfectly fine, for a year. I believe it was ~2500 for a new engine, head and labor.

 

They did remedy the problem with the "Tupy" casting. Not sure exactly when but if you pull the oil cap off as you can see in the pic the "Fixed" head will say "Tupy" stamped on the cylinder head directly below the oil cap.

 

I have an '01, zero head problems (so far) 200k miles.

 

I wouldn't over look a 00-01 Cherokee, if the cooling system was taken care of with regular maintenance and has never been over heated it should be fine. But the 0331 head is a real gamble.
My 00 with the 0331 head that I drove off the lot new, never over heated it and kept up on maintenance still cracked. But I know guys that have the original 0331 head and have no issues. Some time in 01 they fixed the 0331 head. Fixed 0331 heads have the word TUPY right under the oil cap.

Pic of the new 0331 Tupy head. Open oil cap look inside for Tupy


This is what the oil cap will look like if the 00-01 has a head problem or head gasket problem. Milkshake brown under oil cap


This is what the 0331 head crack looks like if you look down inside from the oil cap opening.


another pic of the sweating crack



Like I said just make sure if looking at 00-01 to check and make sure the cooling system looks nice and green, not brown rust water.
check the oil cap for brown stuff like in the pic. Take a flash light and take a look down in there between 3 and 4 cylinder for the crack.
hope this helps

 

Is checking this gonna be kosher for the guy selling it? I don't need to bring any special tools, right? Just open up the cap and look inside for either 1) TUPY or 2) a crack.

Just want to make sure I don't muck anything up with some guy's vehicle.

Thanks everyone for the information! Very helpful.

 

yeah if he doesn't let you take off the oil cap that's a bad sign. You won't necessarily see a crack so it'll either be, TUPY, chocolate milkshake, or neither.

If you can make sure when you see it that the jeep hasn't been run in a few hours that would let you check under the radiator cap too. An honest seller would have no complaints about this.

 

Just a bright flashlight and some good eyes. Take the oil cap off look for brown milky stuff on the underside of it like in pic. Take the flash light look down inside and look for a fine crack between 3 and 4 cyl. like in the pic with the red circle.

A good way to find the crack is to drive it, bring it to operating temp,park the Jeep shut it off wait 4mins take the oil cap off and start looking for water sweating out of a crack like little beads, its not hard to miss.

Now understand your not going to know if its going to crack, you are just looking to see if its already cracked.

 

Right, understood. Thanks everyone!

 

My understanding is that all 2000 and 2001 XJs came with the original crack-prone 0331. Chrysler quietly switched to the TUPY foundry around the beginning of the 2002 model year for other Jeeps with the 4.0L, but I don't think it ever made it into any of the XJs from the factory. If you find one with a TUPY head, someone has swapped it in already.

Not as long as you completely understand what you're risking and are willing to risk it or fix it. What's really sad is when we have someone make his first post on here full of excitement over his new purchase mixed with concern over weird head crack symptoms he can't diagnose, only to find that his new toy has a serious problem. Unfortunately, it's not an infrequent occurrence.

I'm not sure there's a reliable answer to that. The polls I've seen on the internet suffer from self-selection bias. People who have the crack are more likely to find the poll and vote in it than people who have no problem at all, so cracked heads will be over-represented in just about every internet poll.

That said, it's still a serious risk, even on a truck that has been well maintained. I've had mine since I drove it off the lot new. I followed the maintenance schedule to the letter and never overheated it. Mine cracked anyway.

I personally would be willing to buy one under certain circumstances, but it's not something I would recommend to a newbie unless it's someone generally comfortable with auto repair willing to do the research on it.

If you preemptively replace it before it cracks, it'll cost you from a couple hundred bucks up to around $1000, depending on what you replace it with and whether you do the work yourself. Average is probably in the $500 range, since a new Clearwater head will run you about $450. It's possible to get cheaper with a used TUPY 0331 or older 0630 head, but remember that a used head will also require a trip to the machine shop to have it checked at a minimum.

The full cost of replacement can go up rapidly if you wait until it cracks, because as soon as coolant is in your oil, it's starting to damage your bearings. Then it's a matter of whether you catch it in time to save the bottom end. If you get exhaust gas in your coolant, it will boil the water out of it, leaving brown sludge behind that sticks to everything, clogs up the water jackets and can eat a water pump.

Moderate. It really depends on how mechanically inclined you are and whether you do your homework. Swapping in a Clearwater is easiest. If you swap in an older 0630, you'll have to do a little more work to deal with the coil rail on the '00 and '01, since the 0630 isn't set up to hold it in place.

One big problem is that all these 2000s and 2001s hitting the market now are priced too high to justify the risk. Also, you have a lot of them coming available because the head is already cracked, and the owner has changed the oil and flushed the coolant to try to unload it on an unsuspecting buyer who has never heard anything but great things about the 4.0L.

I said above that I would buy one under the right circumstances. Those circumstances would include a low enough price to still be a good deal after adding the cost of a preemptive swap. If I were buying one, I would definitely plan to replace that head before it cracked so that I could have confidence in it. There's a big difference psychologically in knowing you can rely on your engine and wondering if or when the head's going to pop.

 

If you want a off road jeep when you lift the 00-01 they are low pinon in the front which can make things ticky.

 

Proud owner of 00 xj... It's cracked and I'm broke so.... It's a gaint pain I only drive max 20 miles a day and change oil every 1000. But I'm playing with fire if u r broke like me and a novice mechanic I would avoid personally. Wish I had know about this issue beforehand. Would have never even considered buying it, just look for older model.

 

Well crap i just bought my 01 two weeks ago and i had a 2000 before that never gave me head trouble. I just looked under the oil cap, no milkshake, no visable crack yet, but no tupy either. Well boys looks like im riding this train to the end, its only got 130k and it was a oregon state fleet rig so it seemed to be well maintained. At least i can plan for it now i think when its time to replace it i will go with a preformance head sence i will be replacing it anyways and maybe i will get a boost in power. Does anybody know of any good preformance heads. On a different note ive been on here off and on sence 2011 and i never remember seeing anything about these heads before, i geuss i should spend more time on here.

 

I would look in just in case with it running and warmed up look for small bubbles or drips,if ones there it will be right level where the oil flows between rockers. I hope u don't have one. Couldn't see mine with it not running and I have no milky oil. But as far as performance heads go $$$$. But from what I understand Clearwater seems to be a good head, that's what I'm putting on nothing fancy but its beefed up so it won't crack as easy.