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One issue nobody has mentioned is the valve rotation problem. '00-'01 4.0L motors are subject to the TSB for a problem with the valves in which they don't rotate properly. The valves get stuck in one spot, then build up carbon deposits that prevent them from closing all the way, resulting in misfires. Then the combustion chambers have to be cleaned, and the valves have to be manually rotated. It's not a big deal if you know about it before it becomes a problem, and it doesn't seem to affect a large percentage of the XJ population.
As was mentioned above, there are two versions of the emissions in the 2000 models. The California/"50 state" version had two extra catalytic converters under the exhaust manifolds, for a total of three cats. They also have four O2 sensors around those two extra cats, which gives you twice as many points of potential failure. CA emissions XJs were sold all over the country and were marketed by Chrysler as "50 state emissions," because 50 is better than 49, right?
No, not really. The EPA/Federal/"49 state" version only had one catalytic converter in the traditional spot in the rear, with two O2 sensors. Where the precats are in the CA version, there are just straight pipes in the EPA version. Not only is it simpler, but it usually produces less heat and usually makes the heat soak issue less severe.
2000 was the only year you had this choice. All 2001s had the dual precats. The 2000 EPA emissions XJ is slightly more desirable if you can find it, but don't let that make your decision if you find a good deal on a rust-free CA version. All the issues with the precats can be managed.
As for the head, you have choices:
You can learn what signs to look for and run it like it is, then replace the head IF it cracks. The percentage that does crack seems to be over-represented on the internet because nobody runs to the internet to post about the day his head didn't crack. Many people go hundreds of thousands of miles with no issues. So you can run it and be ready for the swap if it does crack.
You can preemptively swap the head with either an aftermarket 0331 or a Tupy 0331. Clearwater/Odessa Cylinder Head in Florida sells new 0331 heads that are cast in China with a thicker deck to prevent cracking. They cost around $500 and come mostly ready to drop in on a Saturday afternoon.
The Tupy heads were Chrysler's solution to the cracking problem. In 2002 (after production of the XJ was over), they moved production of the 0331 to the Tupy factory in Brazil. Tupy added nickel to the alloy to prevent cracking. You might save some money by finding a Tupy head in a junk yard and having it checked in a machine shop, or just buying a reconditioned Tupy head on line.
Promaxx sells a replacement 0331 through Summit Racing. It costs more than a Clearwater head, and I have yet to hear any feedback to justify the higher price.
You can fit a 0630 or 7120 head from an older XJ, but it will take a bit of light fabrication to make it work. The exhaust ports are larger on the older heads, so they don't mate up to the '00-'01 exhaust perfectly. You can buy or make an adapter plate that prevents leaks, or you can install a header with a wider flange that seals off the ports. You also have to rig up a bracket to hold the coil rail on the '00-'01 motor, but that's easy.
If it were me, I would approach it like this:
If this were my only vehicle and my daily driver, I'd go ahead and replace the original 0331 so that I could have complete confidence in it. You don't want to keep driving one once the head cracks, so I would prefer to do the swap on my timetable rather than have it crack at a particularly inopportune period in my life.
If I had another reliable vehicle, I'd just run it as is and watch for symptoms. That way, if it never cracked, I'd never have to spend the time and money on it. But if it did crack, I'd have something else to drive until I could fix it.
Should you buy one? I can't answer that, but I will say that the distributorless ignition system in the '00-'01 XJs is the best ignition ever put on the 4.0L engine. When something does go wrong, the computer will keep you running long enough to limp you home when earlier motors would have quit. Aside from the 0331 head, which is a known, manageable problem, these years are every bit as rugged and reliable as the previous years.
Originally Posted by Tbone289
2000 XJs with federal emissions don't heatsoak any more than '97-'99 XJs. The '00 and '01 with California emissions have the grater chance to heatsoak with the 2 extra pre-cats on the headers.
It does happen with the EPA emissions also. Mine did it before the engine swap, but it was very mild with just a little stumbling on hot restart that smoothed out fairly quickly and never threw a code. The difference seems to be not that the CA vehicles do it more often, but that when the EPA version does it, it's not as severe.
For the OP, there are fixes for the heat soak problem. There's a TSB that specifies a heat shield and an insulation sleeve for the #3 injector that usually fixes it. DEI also makes a complete fuel rail and injector insulation kit that covers considerably more than the OEM fix.
Originally Posted by SexyDexy
As long as you don't overheat the motor, they are just fine.
False. I owned mine since I drove it off the lot in June 2000 with 6 miles on the odometer, so I know for a fact that it was never overheated and was maintained to the letter of the maintenance schedule. The head cracked anyway. Some of them just do that. There's no way to know if you're one of the unlucky ones until it happens.
Last edited by extrashaky; Dec 14, 2017 at 10:14 AM.
It does happen with the EPA emissions also. Mine did it before the engine swap, but it was very mild with just a little stumbling on hot restart that smoothed out fairly quickly and never threw a code. The difference seems to be not that the CA vehicles do it more often, but that when the EPA version does it, it's not as severe.
More so than '97 - '99 as I stated? Why?
Mine does it on rare occasions when shut down hot in the summer, but no more than friend's earlier OBD-II models. It shouldn't be any worse than any of the models without a fuel return line.
Last edited by Tbone289; Dec 14, 2017 at 11:13 AM.
Here is some more proof that the 0331 heads do indeed crack and destroy things if not treated. Miles at time of death 217k. And it looks like it has been leaking for a very long time.
Well, for one thing, it might be that the '00 was designed to run a little hotter than the '99. The electric fan doesn't come on in the 2000 until the coolant reaches 223°.
It also might be affected by a difference in heat radiation or retention of the cast iron manifolds. They went from one steel manifold in '99 to two cast iron manifolds in 2000 with a gap between them right there under the #3 injector that likes to overheat. Does the steel cool off quicker? Slower? I don't know. Does the gap make a difference?
It might also be affected by the downpipe, even without the cats. For all we know the twin downpipes may radiate heat differently from the single pipe of its predecessor. The point is that the precats weren't the only difference.
I should also clarify what I wrote above about how often it happens, as I realize that can be interpreted two ways. I'm saying that I suspect that any 2000 XJ you buy will have about an equal chance of developing a heat soak problem, regardless of CA or EPA emissions, while any CA XJ individually will experience the problem more often and with greater severity than an EPA XJ with the problem. That would lead to a lot of people with EPA XJs not really noticing it. I had rough hot starts for years, but they cleared up so quickly it didn't occur to me that it was a known issue until I saw all the posts about the CA XJs throwing codes.
I bought my jeep xj 2001 less than two months ago the lower radiator hose burst causing it to over heat replaced lower hose and thermostat and drove it home only to find moisture coming out between head and block. Autozone replacement head for About $360 plus $50 core charge. (mainly got this head because they only wanted $50 for the core charge everyone else was much higher)
The reason for the over heat was a jacked up thermostat (looks like previous owner tried to punch a air bleed hole in it ) well anyway a new head ,gaskets, and also replaced lifters it is running fine again.
So would I consider this a good jeep Heck yes and bought it for $2700
No problems.
Paid 4995.00 for it 175k on it at that time. It's clean.
I agree w/ the idea of buying the latest model year possible, it just makes sense.
It possibly still has the original head on it.
It's not a tupy.
A 185 thermostat, new radiator, wp, hoses, relay w/ adjustable thermostat for the a/c fan and a new oem mech. fan clutch are the best way to prevent the head cracking issue. Imo of course.
Just bought a 2001 Limited a few months back. The head wasn't cracked, but I didn't take any chances and replaced it with a Clearwater HD head. My best advice is to put in 4 hole injectors(search around on here, there's a few people who sell them), and replace basically the entire cooling system if you want to be extra cautious and make sure the Jeep will run forever. I was skeptical about buying a 2001, but like a lot of other people are saying, they get a bad wrap. they are still great Jeeps. No matter what year you buy it will have its own quirks. Just inspect it well and make an informed decision.
I have a theory for you guys. It seems that 99% of 2001 heads crack but the 2000 guys are more of a 60% group. Mine is a later model 2000 and it cracked. When I pulled my head it had "00" cast into it. Im sure 01 models have "01" cast into them. I was recently given a 0331 head that has "99" cast into it. Its going on my engine even though I know it might crack. It was free so might as well. I have no problem taking the chance. So, to those of you who have experienced a cracked head, what year was cast into the head? For those of you who drive a 00 and havent cracked a head, whats the manufacturing date on your Jeep? Just wondering if anything changed between the 99 and 00 cast 0331 heads.
Probably a good idea to rebuild/modify the entire cooling system no matter what year XJ you purchase, I hear they overheat.
I'm still trying to figure out why people think a distributor and spark plugs wires are better than what's used on the 2000 and 01's.
No distributor, and the CNP set up seems to work fine to me.
X2
Definitely rebuild or modify the cooling system no matter what.
Lots of people think the coil pack is not as good because the viper coil pack mod is pretty much the only upgrade for it unlike the multiple different upgrades for the distributor and wire setups. The truth is the coil pack makes plenty of spark and ignition power for 4.0s even when modified or even for mild strokers so there is no real reason to upgrade it. Just my .02
Well, for one thing, it might be that the '00 was designed to run a little hotter than the '99. The electric fan doesn't come on in the 2000 until the coolant reaches 223°.
It also might be affected by a difference in heat radiation or retention of the cast iron manifolds. They went from one steel manifold in '99 to two cast iron manifolds in 2000 with a gap between them right there under the #3 injector that likes to overheat. Does the steel cool off quicker? Slower? I don't know. Does the gap make a difference?
It might also be affected by the downpipe, even without the cats. For all we know the twin downpipes may radiate heat differently from the single pipe of its predecessor. The point is that the precats weren't the only difference.
I should also clarify what I wrote above about how often it happens, as I realize that can be interpreted two ways. I'm saying that I suspect that any 2000 XJ you buy will have about an equal chance of developing a heat soak problem, regardless of CA or EPA emissions, while any CA XJ individually will experience the problem more often and with greater severity than an EPA XJ with the problem. That would lead to a lot of people with EPA XJs not really noticing it. I had rough hot starts for years, but they cleared up so quickly it didn't occur to me that it was a known issue until I saw all the posts about the CA XJs throwing codes.
My fan in my '00 comes on at about 210 degrees. Assuming my temp gauge is reporting the correct temperature. I just replaced my CPS. Jeep was just dying, no sputtering (like you turned off the key), and would start right back up. This is a little bit after if reached operating temperature. No wonky gauges, CEL's, or pending CEL's like I read about. Let it idle for the longest time in the driveway after the swap. Fan must of have kicked in four times all at about 210. One thing I have not had a problem with is heat soak or misfires. It is a CA version. When I first bought the Jeep, as I stated before it was a bit of a fixer upper, I did not have the problem. Reading about it everybody was throwing in the 2 cents about what plugs to use. When I got around to replacing the plugs my logic was she was getting new plugs of what she already had in there. Turned out to be cheapo Champions. It had the heat shield on top of the manifold. Pretty beat up. When I did the 4 hole injector upgrade I bought a new one. As far as the cooling system goes the radiator was shot so I replaced that, did the thermostat, and all the hoses too. I have plans on doing a lot up front in the spring. It will be time to dump my anti-freeze (do it every 2 years), upgrade the battery cables, headlight harness, going to try and fix my AC again maybe put in a new condenser. Thinking about putting in a tranny cooler. Thinking while I am there might do the water pump, idler, and replace the adjustment rod for the belt.
