Thanks Dah, I changed the expansion tank cap with a ford part and i realised that i had been filling it to the absolute top with water ... so above the max level.... wonder if the steam and water loss was due to that? the water level is now within the min max levels after replacing the cap i drove around town and motorways for about 100 miles... the temp guage ranged from middle to right into and passed the red... but it didnt over heat. I also noticed that the water level in the expansion tank has stayed at same point. i have run the car at both fully cold and fully hot on heater gauges and this made no difference. a mechanic said the stat isnt a problem... but as you say, for a few bob and some work... it cant do any harm. Thanks