So, it appears that there was an airlock in my system.... releasing it was fun!!!
Thats some serious overheating!! (and yes the water is always kept topped up! )
Question is... WHY??
After some digging round, it appears the most common cause is the thermostat housing, causing a fault with the thermostat itself also. I'm hoping that it is not anything more sinister. what else could be the problem?
Anybody else had this problem? Any advice?
The water was flowing back into the expansion tank... so no problems with the water pump?
(sorry for the randomness of the post.... Boss is hovering!!)