help with my vaillant combi

[chrisreef]

can anyone help me with a problem on my vaillant combi vcw gb 242e,I keep losing pressure on my top up ,I top it up to the mark run a bath the pressure drops then it will go right up to max then during the night when central heating is on it will gradually go to zero then next day I have to top it up again,I can find no leaks on system and we had a new heat exchanger the small one about a year ago.Any suggestions would be appreciated

 

[jj4091]

Sounds like the expansion chamber is either leaking or needs re-pressurising.

 

[Gees]

Or the pipe feeding it is clogged up.
You may have been better off in the right forum..