I just replaced my thermostat and I went for a test drive around the block to try to heat it up. The first time around the block was fine, but a few minutes later, at the next stop light the oil light started blinking and it sounded like it had a nasty ping. I got on it and out of the rear view mirror i noticed white smoke coming from the exahaust. Now the car is making a bad ping at idle and I can hear a knocking from the top part of the motor. Any ideas? Please help!!!