Loud rattling noise under hood then car dies! help!!!!
 

ok so i just bought a 2000 740 il with 120 k on it. engine looks super clean on iside. ok so i had the car for the first 3 days and worked perfect. i bouhgt the car with check service engine light on and thought it was the oil change light :'/ anyways it started making this really loud rattling noise and i ignored it and everyday it got just a tad louder. then the other night i was driving to get munchies and the car starts to sound like it has a huge exhaust leak. so it started off as a large rattle like the fan clicking against a piece of plastic and then it finished off dying on me sounding like the exhaust pipe fell completely off. car still cranks but no start. and i read the code while the car still ran and i had a knocksensor code. any possible relation to the failure here??? i found a video on bimmer forums.com and i will post it up sounds exactly how my car sounded like thnx any help will help please trying to fix my car that i bought for my girl asap.