How to replace the radio antenna on a MkIV

It's pretty simple and if it's just the mast that's broken, you don't even need to remove the motor from the car. To remove the old mast, unscrew the antenna mast nut (on top of the antenna on the outside of the car), power on the radio and be ready to catch the mast when it pops out. Putting the new mast in is just reversing the process. Feed the new belt into the hole (teeth facing towards the rear I believe), turn the radio off, and guide the belt and new mast in. Replace the mast nut and you're done.

If the belt broke, you'll want to take the motor out to get any pieces left in there. You need to remove the right rear panel that hides the motor - you will have to remove the rear strut tower cover as the panel is partially covered by it. The motor is mounted with one (1) 10mm bolt and is pretty easy to remove. Once you get it out, undo the four screws that hold the spooler together and pull it apart. There is some kind of seal material that hold the parts together but it comes apart fairly easily. Inside you will find a white plastic ring that guides the mast belt as it is taken up by the motor. If your belt is broken, part of it will still be inside the white ring. Remove it and reassemble.