Boot leak
 

Upon opening the boot for the first time in a couple of months I was greeted by an unpleasant cascade of water running from behind the boot lid carpet out of the window end of it and out of the bulb change hatch :eek: I then checked under the boot carpet and found about an inch in the spare wheel well. Clearly it’s been sneaking in for a while! Is there a common leak point in the boot lid? I’m guessing round the lights but peeping up with a torch revealed little but condensation on all the metal areas. The lid itself appears to have a couple of small bungs at the bottom in what I would assume will be drains to outside which I’ve popped out for now so anything sneaking in can just run out of the bottom and brought the carpet indoors to dry as it’s soggy along the bottom. The wheel well fish bowl is dried and the spare sat in the boot for now. Any pointers welcome! +++

Its the rubber seal round the bootlid tail lights. These are bonded to the plastic light housing, but when they are hit hard by a pressure washer to blast the moss and slime out of them the pressure pops the bonding apart leaving a capilliary path for water to get in.

My solution is to remove the lights and clean them carefully with a toothbrush then dry them thoroughly, then I use Loctite 480 to bond the rubber back in place. This is a rubber-reinforced cyanoacrylate-based adhesive which wicks all the way round the rubber seal and bonds it back as it should be. Leave it overnight to set up thoroughly and then refit the light unit.

Some cars have butyl rubber behind the light to accomodate the joints in the sheet metal of the boot lid, which can usually be reused. Others have a small dab of silicone sealant instead, which can't be reused. In those cases, clean it off both parts and apply a new small dab of sealant.

+++ muchas gracias. Tiny hard to get at nuts and bolts jobs then. Job for the weekend. Until then the drain plugs being removed should at least let it out.

And a response with the fix from the guru in less than 25 minutes! :D

I had this on my first A8, and really struggled to fix it- I extensively sealed up all the rear lights and the rear number plate area- but in the end it was a seal in the o/s/f corner of the boot lid underside that had failed (so near to the lower corner of the rear window).
I just got a 3D printed replacement for my S8, from MikkiJayne as its had gone the same way.

Actually, your leak seems a bit different- mine was water going inside the boot lid.

Here's that thread anyway- it might help.
http://forum.a8parts.co.uk/showthread.php?t=191