Car is running smoothly at first but once it gets hot or if the car stays on the road for more than an hour ive notice rattling sound from the hood everytime i step on the gas pedal. Car although does not lose power but the sound is annoying. Theres no sound when the car is idle. Cant seem to find the cause of it. Im using corolla 1997 gli 1.6 with 110k mileage. Please help. Thanks