I did this the other day, I didnt like the color of the coolant, so i took it in to a shop to have the coolant system flushed. man was it bad, Now all nice new stuff in side, nice and green, i didnt know it needs to be done every 2 years or 30,000 miles. i have had my XJ just about 2 years. so @ least i know that is done. they said it breaks down and can get acidic, and eat your engine parts. well just thought i would share that, no big deal