So for starters, let me say that there is an extremely helpful post that is on this form that says how to take off the bumper cover from an Audi A5. Assuming it was a B8, NOT a B8.5 model.... Very good write up, with excellent pix and notes.
With that being said, the Audi A5 B8.5 models have a few subtle differences in how to remove their rear bumper. I will try and add photos to this post later. But I have listed below the changes, or like I said "differences" between the A5 B8 & B8.5 bumper cover removal steps.
My car is a 2015 A5 B8.5 Quattro S-Line Prem. Plus 2.0T (for what it's worth, I'm fairly positive the S5 bumper cover removal will be similar to this.)
Tools I used:
Cordless Drill with a bit that has a socket fitting (optional, but man was it super helpful and a time saver.)
Flat blade screw driver
Torx #25 screw driver
Torx #25 bit socket for a 1/4" drive ratchet
Torx #20 screw driver (or socket)
Torx #40 socket (and 3/8" ratchet)
Deep well 10mm socket (1/4 inch drive)
a 6 inch or longer 1/4" ratchet extension
a 3/8"s drive ratchet (extension optional)
a pair of dikes (to cut zip ties from bumper cabling)
2 - Black zip ties (Yes, Audi used zip ties on the rear bumper cover. Replacement zip ties must be medium in size to fit)
Any sort of blunt plastic sturdy object to help with pushing the diffuser clips off the inside of the bumper cover (DO NOT use a flat blade to push the plastic tabs "out". Just use the flat blade to wedge them downward, and then use the blunt object as a "pushing" device to push the tabs out. (You can even use the handle of a medium sized 3/8" drive ratchet.)
This tool list made my job "possible/easy" to do, so that I didn't have to take my wheels off. You can still do the job without items such as the 1/4" ratchet, and #25 torx socket. I used them because it allowed me to leave my rear wheels on. Personal preference, as well as the tools you have available.
Steps I performed in this order:
1. Removal of 3 Torx (#25) screws in each of the rear fender wells (still same old process).
2. Removal of 3 Torx (#25) screws from underneath the car. (still same old process).
3. Removal of a black plastic "push clip" that is removable using the flat blade screw driver. (New B8.5 A5 S-Line feature to remove)
4. Removal of 2 black square plastic knobs that has 4 holes in it that holds tail lights in. I used a short awl. You can use a small/skinny screw driver too. (still same old process).
5. Give the tail lights a firm pull carefully, and they will pop out.
6. Unplug tail lightsThen you can fully remove them.
7. Removal of 2 10mm nuts that are inside the body of the car that help hold on the bumper cover. (I used a 10mm deep well socket, and an 8 inch long extension for a better reach)
***Be careful with the 10mm nuts.
If you drop them, they may
be gone for good if you don't have a magnet for retrieval.!***
I dropped mine inside the body, and it was a MAJOR PITA to fish out with a magnet.
Now, here's where some new B8.5 items differ from older B8 bumper removal process.
8. There is no longer a "white" peg that holds the corners of the bumper on behind the tail lights. 2015 Audi A5 B8.5 has replaced this with a "vertical black plastic #40 Torx screw" that is in a fixed position. The #40 Torx screw moves a "slide lock" mechanism that travels "up/down" the vertical Torx screw. This is what helps hold the bumper on below the tail lights. The tail lights MUST be removed to get to these slide locks.
When you turn the plastic Torx screw "counter clockwise" it will lower the slide lock and allow the bumper cover to loosen. Once the slide locks are fully lowered the bumper will detach easily (with a firm pull using your hands). Be aware if you lower the slide lock too far, it may pop out of the rail.
It's ok, if the slide lock pops out or falls out. It can be placed back in while the bumper cover is off of the car. But it must be with the #40 Torx screw threaded into the top slightly.
9. At this point you should probably have a large sheet of cardboard, or blanket on the ground to lay the bumper cover on. This is because there is a cable connected to the bumper cover on the Right Rear portion of the bumper cover for the rear object sensors. It does not have a master connector to unplug (unfortunately, which is a minor pain in the ass.)
If you try to unplug the connectors from the bumper sensors at the "silver boxes" you may end up breaking off the plastic clips.
10. Instead, I used a #20?? Torx socket bit with my cordless drill to remove the 3 Torx screws that hold the silver boxes into the bumper cover.
11. Next, You can then start to unplug the smaller black & gray bumper sensor plugs with a flat blade screw driver. You can use the flat blade to slide back the "gray T-tab" lock of the connector towards it's wire to unlock them. Once "unlocked" the connectors will then slide off.
12. In the center of the bumper cover there are 2 locations where the wires for the sensors are zip tied to the bumper cover. I used a pair of dikes to cut the zip ties. During re-installation I had black zip ties on hand, and used them during reassembly of my bumper cover.
13. Using a #20(or #25) torx driver, remove the single screw near the corners of the bumper cover & diffuser. (1 per side)
At this point you get the pleasure of removing the diffuser from the bumper cover.
I found that it was easier to remove the diffuser/valance with the bumper cover laying on a clean thick blanket, paint side down. You can use towels, or whatever you have on hand.... Totally up to you, and how you want to do this part.
It's possible to remove the diffuser with the bumper cover facing up towards the sky, but it makes it more difficult. Just be careful while you're pushing the tabs out, so that you don't tear or deform the plastic tabs of the bumper cover. They're not very strong.