Try to understand me because i'm not really good in english. Water began to boil at 100°c. The cooling fan of the ak12 cr12de start turning when the engine reach 102°c. 102°c is too much for the radiator and the to evacuate all that heat. This only two solution,first one is to swap the radiator for a bigger one. The second is to modifier the cooling fan to make it work at 90°c. You can do both of the solution if you want.