Boiling is problem, see below expected reasons in points:
1- Head Gaskit: if it would weak then pressure would be increase in radiator. u can check ur self either gaskit is wear or not. start ur car, open radiator cap. make sure that radiator filled with water. u will observe that in few seconds some bubbles will appear in water, if appeared then head gaskit is weak and leaking pressure. Replace it.
2- Fan: Check that fan is working properly. U cannot adjust the speed of fan.
3- Radiator cap: filled radiator with water till top. Close the radiator top with pressure cap/radiator cap. there is a samll pipe going from radiator to bottle. remove that pipe from bottle and give the air pressure through ur mouth, in that way if water comes out from the pressure cap then pressure cap useless and replace it urgently.
4-Water body: Check that water body (which rotaes water into the engine and radiator) u can check this by removing pressure cap from radiator (car should be in start position) u will observe that if u will push the throttle then water will moves into the radiator.
5- Any leakage: this is very importan point. check leakage at all start and end of all pipes joinied through radiato/engine/ fan heater etc. check all clips are properly tight.
these are my personal observation share with u, call me at 0321 4414134 in case of any confusion.