i just got my 2002 mustang and when i go in reverse or first sometimes when i first get in the car after it sit for about 10 hours itl make a loud horn noise kinda thing.. it sounds like its comin from my rearend the tip the guy before me put on is rubbing against the bumper but i cant see that being the problem.. any suggestions? thanks in advance mostly does it in reverse

 

Its hard to say. If it is easy to reproduce, have a friend sit in the car and reproduce as you stand outside the car to try and pinpoint the noise. If its as loud as you say it shouldn’t be hard to find. Good luck...