I'm new and this is my first thread, but thought I would share since I actually solved the issue, and mostly out of frustration. I bought a 2008 A 4 S-Line 2.0 with really low miles but like everyone on this thread, had the same issue with the seat "back" covers falling off. I tried everything including double sticky tape, a glue gun, 3M velcro, and crazy glue, but nothing worked. As soon as the ambient temperature got hot, the seats would fall off! However, you're going to kick yourself when I tell you the answer!! I actually found it online. Use crazy gel glue and baking soda! Insane but when you mix the two, you'll need a chisel or jackhammer to remove it. The baking soda chemically reacts with the glue and produces a hard epoxy-like material, plus it cures in record time!!!! When I first tried it, I didn't do a good job because I used a small tube from the dollar store, and due to the fact it was runny, it was hard to work with. Yet, several sections still held! However, I bought the gel version on Amazon and whamo - it's still holding - like cement!!!!!! I still can't believe it worked! With this concoction, you can repair anything plastic! For example, my windshield wiper tank was also leaking and I was about to buy a new tank. Instead, I found the leak, cleaned the area, applied crazy glue and baking soda, let it cure for about 12 hours and IT HELD! No more leaking!!! I have to warn you, it's going to be messy with the baking soda, but it's cheap and I promise you nothing you do will be cheaper or more effective! To keep this in perspective, if I tried to remove the covers today, I would essentially destroy the backs of the seats, i.e. leather, because of how firmly their attached!

Use plenty of baking soda and make sure you have plenty of ventilation and please use gloves - safety first. Be really careful with this stuff because it's not forgiving! Work quickly and smartly, but you'll love the results! Here is a great video demonstration regarding the use of baking soda! Hope this helps and good luck!

 

Wanted to give a quick update. The seats were glued about 2 weeks ago and they're still holding strong! I was in Palm Springs and the temperature got to 110 and the seats held like steel! Problem solved. Good luck!

 

So it's been more than a month where southern California has been ravaged by a heat wave! Long story short, I was in Napa where the temperature was over 112, and the covers held! And, it's still holding! If you pursue this method, you won't be disappointed! Good luck!