vokera expansion vessel?

Try Re-charging the pressure Vessel with a car tyre pump through the valve on the top of the unit, (usually right under the fue pipe)it should be between 0.75 and 1 bar. If it does not hold pressure then you will have to replace it. You can add another expansion vessel to the central heating return pipe (as near to the boiler as possible), this does not involve removing the boiler from the wall, but it does depend on the location of your boiler and the amount of accessible space below it.
if you're not good with pipework then get a plumber.

Phil
April 2007

Last time I replaced an expansion vessel I had to take the boiler off the wall to get it out but this isnt always the case it does depend on the boiler, but having said that it usually does mean taking it off the wall.

Steve
May 2005

have you repressurised the vessel???

d..
May 2005