I have a 2006 convertible bug and Earlier this week my gas cap light had came on and it went off after turning car off and now the CEL is on and I keep hearing a thumping sound coming from rear when car is not moving. It doesn't do it all the time it does it at random times. The car drives perfectly fine. Anyone have a idea what this could be? CEL went off this morning but I still hear the thumping sounds.