Mazda 3 major 4-inch leak in trunk on Mazda 3

Some Mazda 3 owners report experiencing significant leaks in the trunk, which can be attributed to several common issues. These leaks may stem from faulty rear taillight seals, particularly where a white tab is positioned to block a hole but may not be correctly seated. Additionally, the long rubber seal around the trunk lid can degrade over time, allowing water to seep in, especially as it shifts with each opening and closing of the trunk. Other potential sources of water intrusion include the door membrane, cabin filter, sunroof, door seals, air conditioning, and improperly installed lights. Furthermore, some owners find that clogged drain hoses at the bottom of the trunk can exacerbate the issue, leading to water backup, especially when parked on a slope. To resolve these leaks, it is crucial for owners to inspect and possibly replace the taillight seals, assess the trunk lid seal, ensure all potential water entry points are properly sealed, and clear any debris from drain hoses.