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It isn't just the 1.3 petrol engine that suffers this, it is all petrol variants (including the Brabus I believe?) that have this from time to time.
The throttle body is held on by 4x T30 bolts, the air pipework to it, so you'll need a flat screwdriver and a pair of nose pliers to remove the constant tension clamps that clamp the coolant hoses to the body (and it is this that I found the most arduous of the jobs). Undo in order:
- The air pipe work
- The T30 bolts
- The clamps and get a friend to hold the body whilst you undo the clamps
- The electrical connector
Once the pipes are undone, you'll need to stop up the pipes to stop the coolant from spilling out and have something to catch the coolant that does come out.
Installation is the reverse really.