I bought a caddy 2 years ago, I was sold a car wit...

I bought a caddy 2 years ago, I was sold a car with a lot of prombles, took my car back on several occasions and mentioned the knocking noice and was told that everything was ok, and now my car is knocking even worst. Not to mention that Everytime it rains I have a trunck full of water. Service and sales treated me like I was bothering them for the car that I brought from there dealership.