my 146ti is running like sh*t* at the minute, im awaiting new coil packs so instead of going for the obligatory sunday run decided to give it a clean and just kick it in... therewithin my problem, within five minutes the temp gauge had gone off the scale and expansion tank had emptied turned the engine off and let it cool. i released the cap (very slowly) to find the tank refill with air and fluid (mostly air),then within seconds it emptied itself completely back into the system. i let the engine cool some more and then topped the tank up, i then re-started the car and ran it for 15 mins but mysteriously the temp sat just below the 90 deg mark all the time!!!! is the stat on its way out or this a prelude to something more serious??