My wife's 2003 Civic LX sedan leaks water into the trunk only when driven in the rain. I traced this leak on the passenger side to the wheelwell in the trunk. Water seems to be coming into the trunk from between the quarter panel outer skin and the wheelwell. After thorough visual i8nspection, I do not think that the leak originates from the wheelwell. I think that it is coming from higher in the C-pillar. My theory is supported by a rusted 10mm bolt that mounts the rear seat side bolster, which indicates that water is also seeping behind the door opening panel.

Has anyone had this problem? If so, what was leaking and how was it fixed? This is still under warranty, but dealers usually fumble issues like this.