could possibly be the rear door seal, has it been raining? could be water getting in, also a/c drain tubes could do this too if there blocked, seen and had this in my vr, but it was l/h/f floor. car hasn't been in an accident before? could be a panel not lined up properly, just some ideas, my boot used to leak water in my vr, was the boot seal, so could start at the door seal if it looks a little worn and go from there, a good quick easy spot to start, along with drain tubes(checking if blocked and un blocking) before chaseing anything major, good luck with it.
|