I need to change the rear spoiler on my 2005 golf gti.
I read that it's possible to remove the adhesive by cutting through it with some kind of a thread, I guess nylon would be best.
Has anyone done this? Any tips?
If you can work it under the spoiler, dental floss would probably work. That will take care of the adhesive and it should come off if there aren't any bolts holding it on.
I've never done this myself, but on the make/model specific forums I frequent, I've seen dental floss and fishing line recommended. Though going back and searching, it seems the dental floss (doubled over) was recommended for emblems, fishing line for spoilers. You might also try a gentle application of heat to loosen the adhesive, perhaps also (again, gently) applying a plastic putty knife once you've got enough of a gap opened up. Make sure there aren't any bolts holding it on, check from below. Though if you work fishing line from the driver side to the passenger side that should rule out any fasteners.
If the fishing line doesn't work try fishing leaders. Fishing leaders are available that are made of small diameter steel cable. It is available in measured lengths or by the spool. They come in various strengths and are nylon coated which should protect the paint. I have used them to cut thru windshield adhesive. Park the car in the sun for a couple of hours to help soften the adhesive. Use a sawing action and lube the wire with WD40. Once everything starts to separate place small wooden wedges under the spoiler so it won't readhere.