My 1999 v70awd XC has a continuous clicking, which appears to come from the left front (driver side). The vehicle has 180000 miles, new rotors & brake pads 400 miles ago. The axle boots are good, but the right side is loose on the outside end. The clicking speed up with the speed of the car. Has been off & on for 6 months. Sounds like a piece of tin riding on a cog as the cog turns.