It could be the CV joint, but that going bad and making noise would not likely be related to the work you had done. If it sounds like the ball bearing in a paint can rattling around when you take a corner under power, that is it. It could also be a loose heat shield, perhaps the one that protects the catalytic converter. Might even be the fan shroud, that could be loose as the mechanic either had to remove it or work around it to get to the radiator.