did someone actually hit u from behind a long time ago? yesterday i checked my mates sportivo which never been in an accident and the way we sprayed the high pressure water at the jet wash, water still leaked inside the car from the foam seals of the tail light. so it must be a factory fault or something. when i sprayed mine, it was leaking under the latch for the hatch back tail gate and into the spare wheel compartment. which i think it fair enough as i was spraying the high pressure water directly into the gaps at one stage. rain water will only travel where gravity takes it. the pressure of the water shooting will make it bounce upward and into the seals and then into the cabin. your best bet is to wipe the inside clean and go to the jet wash with someone and them sitting in ur car and seeing if any water leaks in from the outside when you spray it with water. just imitate heavy torrential rain. dont go spraying directly into the gaps. see where the point of entry is before you start attacking the car with silicon.