The 2000 model year, along with I think the 99-01-02 with the 4.0L I-6, changed to a different head. The heads that were used, if I remember, is casting #00331, which mine has, and more often than not, will crack.
My experience was that at approx. 140,000 miles, I started losing coolant out of the reservoir. About every 300 miles I had to put in about half a gallon. This went on about 4 months. Couldn't find the source of the leak, no oil in the coolant or no coolant in the oil?
Then later, the crankcase was full of coolant, had it torn down, and sure enough the head had two cracks; one that let the coolant in the combustion chamber, and one that let coolant in the crankcase, so $1500 later it's put back together with a rebuilt head --- yes it was another casting #00331, so we'll see!
(warning) I used a head and block sealer before I went to the expense of the new head. It was guaranteed to seal all cracks. Well when the engine was torn down, most all the holes that let oil lube the valves and lifters, then drain down to the crankcase, were all plugged from the sealer, so if it had worked, I would have had more engine expense.