i have a nissan sentra 2001 2.0 SE with 107,000 miles on it...ok theres a problem when i start the car. when i turn the key the engine starts perfect, just that when i turn the key at the very end i hear a loud noise. so every time i turn the key to start the engine, it makes like a "crank" noise. some of my friends say its the timing belt. i also hear a loud noise on the front right side of the engine...the area where the timing belt is. ok so iv been hearing that sentras have a CHAIN instead of belts and dont need to be replaced. so whats that loud noise in the right side of my engine and why do i hear a "crank" noise when i turn the key to start the engine??? advice plz...thanx.