replacement on 2004 Jaguar XJR

when should a serpentine belt be changed on 04 jag xjr?

2 answers
This depends on the condition of the belt. Look for cracks and for the newer belts the ridges should be measured. For your particular car the inspection interval is every 20K miles. I hope this helps.
There is no interval; I would recommend no more than 5-7 years or 60,000 - 90,000 miles.