if you have never serviced your radiator for 4 years and the water is rusty, do a full servicing it wouldent cost more then RM100.service it and get a good radiator water, not the rm5 cheap radiator water or the 'water wetter' just get the mid range one and you would be fine. you might want to check the hoses too, get it inspected by your mechanic. you might need to replace your hoses too.if your tempreture still rises up then there could be 2 possibilities
1. your water pump is jammed
2. your termostat is scrwed :(