2001 echo. Had the front passenger side wheel bearing replaced. After a few days of driving a knocking sound with a pulsing frequency began when applying the brakes. Took it back twice to the mechanics for attention and the sound would be gone for a week or so and then return. There is some slight vibration on the steering wheel at speeds above 60mph but the noise seems to be exclusive to braking only. Might the bearing have not been pressed in correctly and causing misalignment of the rotor? Any ideas on what this sound could be and what the mechanics are missing or might have done would be appreciated. Thank you.