I've got a real head-scratcher here for those of you who'd like to take a stab at it: When idling at a stop light or even after putting my '01 Elantra in Park and pulling up the emergency brake, I sometimes hear a series of noises from the rear of the car. It sounds as if someone is trying to escape from my trunk—ta-dump, ta-thump, da-thunk! On one hand, when I am at a stop light I can make the thumping sound go away by pressing harder on the brake pedal. On the other hand, when I take my foot OFF the brake pedal after pulling into my driveway and putting the car into Park with the e-brake up, I sometimes also hear the noise. When it happens in my driveway, the thumping noises are loud enough to catch the attention of anyone standing nearby. It can go on for up to a minute before it dies out.
I can't seem to figure out if the noise points to a problem with the rear disc brake pads, calipers, ABS system, rotors, rear struts, brake cylinder(s), emergency brake or even the exhaust muffler. I don't notice any braking problems or suspension issues (although on the front end my car has already had a few odd problems including two new front struts and a new engine mount). Because I can't reproduce the rear thumping noise for my dealer, this has gone on now for four years! If I continue to do nothing—because I can't get anyone at my dealer to troubleshoot a problem they can't reproduce—am I potentially putting myself or other drivers in danger?
Thanks in advance for your help. Also, has anyone else had this problem?