my g/f car has developed a weird problem honda civic 95 model, car will go up to normal temp just under half way on dial and stay that way if moving along, once it idles say in traffic 4 5 mins the needle goes up to halfway then fan kicks in fine, however the needle continues to clime 3/4 up has not overheated yet however, but once starts moving goes back down to half or lower...... coolant has been flushed im thinking it the thermostat maybe? ?