Used car sale

That's a very common problem on any car that sits in a high humidity environment. To prove the dealer right, take it on another test drive, ... For 30 minutes, in city driving. If the pulsation doesn't go away, have him machine the front rotors. Machining is preferable to replacement because even new rotors can warp and need the same service. There's a published legal minimum thickness that must be maintained. If either rotor is near that minimum, then they have to be replaced. New rotors aren't very expensive but might as well get the repairs done before you buy the car.