Installed new front brake pads and new rotors. No popping noise before but the original rotors were worn pretty badly. Now when the brakes are applied there is a constant popping noise coming from what seems like the drivers side front. I checked both sides to ensure proper assembly and that the retaining bolts/clips were tight. I did not clean any parts such as the calipers or rails. They did not look too bad. I did not grease any of the parts either. I took the vehicle for a test drive and got on the brakes pretty hard and heated them up. The noise seemed to have stopped. Drove the vehicle again and the noise is still there. There is no jerking or brake pedal vibration. Any clues?