drop the water down throu radiator drain off.fire ch up ifc it goes over 3.drop the water down till no waters comming out.expansion is red and will have a tyre valve connection.normally looking down from the top off the boiler by the wall.take cap off pump up bike pump will do.put some fairy liquid on cap makeing sure it dosent bubble meaning air escape.fill boiler back to one and test.it should stay well under 3 bar.check outside copper pipe if its dripping you need to clean or change prv
BIGWIG LIVERPOOL
Bigwig
June 2009