Remove the thermostat valve.. Every thing will be fine.. Dont waste money on other things.. These are japanese car and designed according to japan.. The people of japanese not exceed from 65km/hr.. But in pakistan the weather is harsh and the behaviour of driver too with these innocent vehicle.. We speeding 660cc car upto 90 nd 100 nd some people also use AC at that time.. Thats are the reason the car show heat up sign on long route.. But in city, the problem resolved automatically. So dont take tension, remove the thermostat valve or direct the fan, use only 5w30 or 10w40 PS oil for good engine efficiency.. Or keep going waste your money..