Kapag umaabot na sa 3/4 ang gauge indication, normal pa ito for some cars especially those with thermostat at you may notice this during heavy traffic. Above 3/4, you should be alarmed especially if running on clear highway because either water level is not normal or flow of coolant is being restricted by something - a locked or malfunctioning thermostat or defective water pump. Overheat is when the engine stalls so be always mindful of the temp indicator to avoid this.