hi guys I have an 03 plate 1.4 16v with an annoying prob coolant bubbles up out of the expansion bottle (with cap on) I have changed the cap but no better its fine if the heater is on full on screen but within a minute or so of the heater being turned off it boils over again I have bleed the system hoping it was an air lock but its no better my next port of call is gonna be the temp sensor as its gauge has read halfway for the 5 hours ive been mucking around with it but no fan kicking in just wondering if any of you have had this issue