Very straightforward job - Save £££s
I have just done this job in less time than it took to write this guide, OK a bit more but only a bit. My radiator developed a hole at the top so the car was still drivable. If you suddenly lose all your coolant, your car won't be. Don't take it to the garage, they'll charge you a huge sum for twenty minutes work. I urge you to tackle it yourself.
This guide relates to a manual car, in automatics, the method is the same but there are two additional hoses from the oil cooler at the bottom of the radiator to remove and re-attach (you'll need to clamp these two hoses to prevent oil loss).
Socket set with 10mm and 12mm sockets, large cross-head screwdriver, pliers. Also a new radiator (about £30 off ebay) and 2 litres of antifreeze.
Firstly drain the coolant (if there's any left in there), There isn't a drain plug fitted to later K11s so simply remove the hose clips from the radiator end of the top hose and the engine end of the bottom hose (so you don't need to scrabble about under the car). Some coolant will probably drain from the engine. Catch it in a washing up bowl or something similar.
Removing the radiator is vary easy. Disconnect the fan wires (block connector with a catch on the side) unbolt the horn and use the pliers to free the clip on the expansion tank hose (to the right of the rad filler cap) then pull that off (the expansion tank is to the right front of the engine bay, by the battery). Next, remove the four 10mm bolts securing the front frame to the car (two each side, one pair 40mm to the right and the other pair 40mm to the left of the bonnet catch) then the single 12mm bolt securing the bottom of the bracing piece down from the bonnet catch to the front sub-frame.
Lift the front frame away from the car. The bonnet release cable is still attached so just lay the frame out of the way (watch that you don't scratch the paintwork use an old towel or something). The radiator has two pegs top and bottom, these pass through rubber grommets and this is all that holds the radiator in place.
Pour the rest of the coolant out of the old radiator and lay it on its front. Remove the two large screws securing the fan assembly to the rad. The fan has a peg located in a hole on the lower edge of the radiator, when the screws are removed it will come away easily. then remove the lower hose.
K11 Micras rust in the front subframe. Whilst you have access, it might be an idea to wire brush the rust off and give it a coat of rust inhibiting paint... Just a thought.
Fit the fan and hose to the new radiator. Locate the two lower pegs into the lower grommets, offer up the front panel (a dab of soap will ease the pegs into the grommets). Put the bolts back, re-attach the horn and the fan wire. Re-connect the hoses (lower, upper and expansion tank).
Finally re-fill with coolant 1 litre of anti-freeze to 1-2 litres of water (don't forget the expansion tank). Best to use new coolant, not the stuff you drained from the car. The system holds four litres in all.
Bingo and you cup of tea will still be warm!