Which years were XJ heads prone to blowing again?

Was it 2000 & 2001's or did they go earlier back to like 1997 or?

possibly late 00 but 01 for sure. you're looking at the casting number on the head it's cast into the head facing upwards next to the valve cover by the intake manifold. 0630 you're good to go, 0331 start looking for a spare.

you can put an 0630 head on in place of an 0331 with no mods.

Thanks man!

That's exactly what I was looking for!

The year 2000 was the worst year. 2001 years don't seem to be as bad. I did a pole on here and over at Jeepforum to see what percent of 2000XJ owners actually had their heads crack before 100k. Some guys would say that the problem wasn't as bad as they made it out to be. (most didn't own a 2000). In both polls over 100 guys responsed and over 40% of the guys had a cracked head and over %50 of the Jeepforum guys had a cracked head. Another guy did the same pole with the 2001 year and the numbers dropped to around 25%.My 2000 cracked at 78,000 miles. The 0630 isn't quite a direct swap, but close. The exhasut manifold doesn't line up quite right so you need to grind down a few areas. You also need a plug for rear thermostat. You really want to find an 0331 head (direct swap) out of an 04-06 TJ. They don't seem to have the cracking issue the earlier years had. When my head cracked I replaced it with an 06 TJ head, but the motor was too damaged and the replaced head didn't fix the problme. I ended up getting a remaned motor from an 06 TJ and put it in my XJ. You can get used 06 0331 heads online with free shipping for about $250-300 or about $200 at a junkyard but you have to do the removal work. If you need help doing the swap, let me know. It's not too bad, but definatey easier with someone helping.

there is no rear temp sensor in the 0630 head Brad (96+) 7120 is the earlier HO head (91-95) with the temp sender hole in the rear.

GrimmJeeper said:

there is no rear temp sensor in the 0630 head Brad (96+) 7120 is the earlier HO head (91-95) with the temp sender hole in the rear.

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That's right. Sorry about mixing that up. It's been a while since I had to deal with that issue and do all that research. I probably should have looked at my old threads before I commented. I'm glad one of us is paying attention.

Grimm: is it feasible to drill and tap the head for the guage sensor? Or was there a change in the head?

Sean, it is possible but much easier to just get a 7120 head if you need the rear sensor. most people though just extend the wires and drill and tap the thermostat housing to accept the sensor that is supposed to be in the back of the head.

GrimmJeeper said:

there is no rear temp sensor in the 0630 head Brad (96+) 7120 is the earlier HO head (91-95) with the temp sender hole in the rear.

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(out of my chapter, but I saw it in new posts and I'm drunk so... :dunno

the 96 heads and even some of the 97 heads have the temp sensor port (the 97s will have a blockoff plug already installed.) But you can stuff any broken temp sensor from an 87-96 in it, or a 1/8" NPT plug from home depot, for less than five bucks, so it's really not a big deal.