As i was driving today i noticed that the temperature was in the red. so i pulled up at my mates house and let it cool down. noticed there wasnt any coolant at all in the radiator and in the expansion tank. so we topped it up with water and switched the car on to see if the radiator had popped, however it wasnt leaking from anywhere. before this had all happend my heaters never got fully hot, they were warm but never hot, so i assumed this was the thermostat and weas planning to change it but never got round to it. now that theres only water in the system the heaters have started working properly. does anyone know what could have happend. im still confused as to where all the coolant could have gone as ther doesnt seem to be any leaks. the car still drives normal, boosts fine, also doesnt smoke at all. thanks in advance for the help