4Doors

I've read a little about the 00-01 4.0 having a redesigned head which can have issues with cracking or something like that. Can someone shed some light on this for me? I'm looking at a couple XJs, a '00 as well as an '01. The '01 says it has a slow coolant leak and can run a little hot, so I've got to find out if it's a cracked head. Haven't talked to the guy yet, but wanted to do some homework before I got handed a line.

miglia-spyder

Well in late 1999 through 2006 they used a different casting operation for the "0331" head. The head gets the most heat fluctuation between cylinders 3 and 4. This cause a small hairline crack sometimes to small to see with the naked eye! This causes the engine to leak coolant into the cylinder and or on the outside of the head. If you look at the 3rd and 4th cyl, valve springs you might see a line of coolant "crustys". Another way to tell is if your leaking coolant out of the resevoir and cant explain where its going off to. This results in the obvious problem of premature wear on the bearings and low oil pressure (10lbs).

I wish i knew all this when I bought mine... Because even though mine runs great and doesnt get abnormally hot it still smells like coolant every once in a while!

RIDE IT TILL IT DIES!!!!

fishtaconc

the '03-06 heads had this problem resolved from what ive read, you can swap out to #0630 but youll have find a way to mount the coil rail

miglia-spyder

Ive read it both ways... Maybe a couple people just got unlucky.

jeepkid03

Yup, the '03-'06 castings are improved and will have a TUPY stamped into the head.

I replaced the head on my 2000 with an aftermarket one before it could crack. If the 2001 you are looking at runs hot, that could definitely increase the chances of the head cracking, although it sounds like it already might be.