Why is the water overheating

Coolant overheating may be from; a stuck closed thermostat, sealer used to fix leaks, inoperative cooling fan, blown cf fuse, faulty cf relay, faulty coolant sensor, blocked airflow from debris on the ac condenser coil in front of the radiator, etc. If you have an operating ac system, turn it on when starting up a cold engine; virtually every vehicle ac system turns on cooling fan(s) when ac is used since the condenser coil is hot from compressed refrigerant and airflow forces heated air into the radiator behind the c-coil. The fan(s) force airflow to prevent refrigerant pressures from rising too high as well as keeping the radiator from absorbing hot airflow that can contribute to coolant overheating. In addition, a faulty coolant cap may allow coolant to flow out when a pressurized cooling system is required.