Removed the plastic cover by rear taillights and noticed the water flows through the highlighted gaps onto the trunk/boot floor. Should these gaps lead somewhere or be connected to anything?
Looks like you’re in England like me where it’s not stopped bloody raining for 6 months . I’ve had the exact same problem this week. Rain getting into the far left of the boot. I pulled off that plastic housing and the drainage hole was gummed up with mud, grass, hair. Ran a kettle of boiling water down it / unblocked it with a toothbrush. Water is meant to run freely down where I’ve put the arrow. If it can’t then it will overflow into the areas you’ve highlighted and get into the boot.
Similarly, my 3rd generation leaks rainwater into the "boot" when the tight drainage path between taillight and the sheet metal on which it's mounted clogs with leaves, pollen, bits of tree blossoms, etc.
Thanks for that. Yes, rainy England! Beneath the plastic removable cover was actually clear but the car is parked on a slight tilt so when it rains the water flows mostly down the rear right side of the hatchback/trunk door and much if it pours through those gaps. Have you experienced water from the trunk reaching the rear seats or rear footwell areas?
No, never. Only in the boot and only a small amount. Before I identified the problem I actually thought one of my dogs had done a quick wee in there on the way to the park. At its worst it would gather around the far rear left and some would drop into the spare tyre area. It would also go as far forward as where I’ve marked in blue -the rubber gasket but only in small amounts and never into the passenger cabin.
That is excellent. Thanks for the highlighted photo and other information. There is likely more than one leak in my car - one similar to the trunk leak you describe and possibly another which flows down the side edge of the rear seat (slightly soaking the edge of the cushion) and down somehow into the footwell. Will keep searching for the source but will resolve the trunk leak first in case it is connected. There is a good amount of water entering the lower (red highlighted) gap straight into the trunk. Might seal this up but it must serve a purpose? Thanks again.