temp gauge should of shown it!do ya heaters get hot?have you checked the hoses and rad to make sure the circulation is good?you could always run it up get the fans in wait till they cut out then slowly undo the cap,it should not boil over at that stage!i presume you have no nasty noises from the cambelt area?i see you are doing ya belt!always good practise to check ya pump for play and to check the bearing by simply spinning t and see how it feels!(much the same way u would check the wheel bearing!)