Originally Posted by rigwrecker

its probably your expansion vessel fooked top up the water to 1.5 bar click heating on and watch the guage if it goes up to 3 bar it will dump out the water through a pressure relief valve and u will need to top up again this will mean the vessel is knackered u might be lucky and the vessel only needs pumped upthere is a valve like a tyre valve on the top off the vessel vessel is prob behind the boiler so u will find the valve ontop off the boiler at the back take off cover and push pin if u get water vessel is done if just air use a pump to pump up a bit failing that the release valve may be passing