hi there.
i've just bought a lovely 340. it has a few minor problems like idling when cold, but i've checked out other comments on this forum, and hopefully will be able to sort that. the other problem, however, no one else has mentioned yet...
i've noticed water standing in the boot after heavy rains. it's a very slow leak, and the rubber seal is in good shape. it looks like it might be coming from drainage from the tailgate, but i'm not sure what to do about this. does anyone have any advice? i feel like i'm fighting a battle again time and rust...

mine used to puddle on the flat bit just inside the seal, to the left of the number plate. i've no idea where it came from, but i presumed it was to do with a break in the seals.

Mine had a bit come in around the spoiler, but some silicon sealant sorted that. Fake Kar still does, and that doesn't have the spoiler, so I thinks it's down to the actual window rubbers. If you don't watch it it comes in through the lock area, and rusts that away. I'm just gonna put a bit of silicon around the rubbers

Chances are the sealant between window rubber and the car body is cracked and gone. I had that problem at both the rear window and windscreen.

Buy some window sealant at the car parts shop. (I used Dinitrol Window Sealant). It must be permanently-flexible. Clean the old sealant out first.

I have that problem too with my 340 & 360 when I wash the car, infiltrations are possible around the rear lights