Turn you boiler off so that the pump is not running,fill the system to 2 bar and manually vent all rads on the system.Do not vent using the pressure relief as this will cause you problems as this is an emergency feature as should not be messed with.The boiler should then be turned on and the system run for an hour or so, the boiler will vent any air trapped through its own auto release valve.
Andrew Turner
March 2007