Hi there, just changed mine and took down some (very) detailed notes for future... Might be of some help
I noticed that the temperature gauge sometimes goes over the 90 mark after harder driving and the high speed fan kicks in. At the same time I felt that the radiator is partially cold while the top hose is hot and firm, so the rad was most likely blocked. Leaking plastic coolant pipe or punctured and leaking hoses were also symptoms of this. Flushing and reverse flushing with NovaStop Flush or similar high quality cleaners helped briefly as a first remedy, but new rads are around €150 or £120, so i decided it was not worth taking any risks.
Essentially the process is similar to the posts for changing the 147 rad: remove wheels, bumper, undertray and wheel arch liners (c.1hr), disconnect rad, change over (1hr) and reassembly (1hr). Allow a bit more time for cleaning and fixing the odd thing as access to engine bay is easy at this stage. A good opportunity to clean behind the arch liners and even to Waxoil the forward sills.
Tools and Parts
You will need: new rad, red coolant, spanners, TX27 key, water and cleaning stuff, two bricks and wood for support, 4x cable ties and some red rubber and copper grease, also some 40mm jubilee clips, just in case. Takes about 3-4 hours, all fairly easy.
1. Jack up on axle stands. Remove front wheels.
2. Remove both wheel arch liners, held on with 5-6 screws - these can be fairly hidden behind aa lot of muck...
3. Remove under tray if fitted: 3x TX27 screws under bumper, 4-5 bolts underneath
4. Remove bumper: four more TX27s on top and four inside the wing. Disconnect indicator connector at driver side under wing. Pull sides gently outward to move bumper of the two clips, it is free now. Disconnect any other connectors, if fitted. Set bumper aside.
5. Disconnect radiator fan (remove the aluminium cover and blue clip) and resistor plugs. Disconnect air intake. Drain and capture the coolant. My GT differed to other descriptions as the pipes on the rad can be removed easily: the elbow joint on the radiator has two metal lugs. Press these in together with your fingers and pull the elbow loose away from the radiator, no need to remove any pipes. Mind the O-ring inside, though, it is easily lost.
6. Remove the plastic shroud/frame around the aircon rad, held on with 8 or so 8mm hex screws. Some can only be accessed when lowering the rad assembly!
7. Remove the steel bottom bracket, 2x 13mm bolts each side. Have some bricks and wood handy to support the rad assembly when it comes down. Now remove remaining 8mm screws and remove both the shroud and aircon rad. Mind that there are also two clips on the bottom holding the shroud to the rad. Support the aircon radiator with cable ties, remove the shroud. Careful not to damage the oxidised fins or connections.
8. Lower down the rad and fan assembly and remove it completely.
9. Remove the four screws that hold on the fan frame and remove it. Give everything a good clean, particularly inside the pipes where accessible. They are probably quite bunged up. A bit of red rubber grease on pipes, o-rings and grommets will help to keep the rubber supple. Gently clean the aircon rad and oil filter with compressed air, if available.
10. Fit the fan to the new rad, relocate it, bolt aircon rad and shroud back on. Make sure the radiator lug on top goes into the bracket with the hole and that you have not forgotten the rubber grommet there. Then the base bracket goes back on.
11. Rest of the reassembly is the reverse of the first nine steps. A bit of copper grease on bolts eases the work next time...