i am using this car since last four years. had been running perfectly without any major issues. few weeks back, one of radiators pipe got bursted and car heated up. i got it checked up, new pipe installed and no other damage was observed. now once in a week, while driving, the temperature needle starts to rise from middle position (normal position) it goes up and than falls down to normal position. i have observed that with the passage of time, its peak position is rising. Mechanics have failed to understand. kindly help.