High pressure in combi boiler

[james789]

Hi,
My Bosch combi boiler is making loud noises with pressure gauge reading almost 4. I have turned off the mains supply and the noise has stopped. At the moment the central heatinf system is off, but normal domestic water in use. Do you think this is a faulty pressure relief valve ?
I look forward to suggestions

 

[migoplumber]

has somebody accidentally opened the fill up loop?

the prv should of blown off at 3bar so yes there appears to be a fault with that too.

shaun