Grant Vortex combi boiler problem

[Daddles]

Hi, I have a Grant Vortex 26e internal oil fired combi condensing boiler and the pressure keeps dropping to zero.
When I top up to 1bar and run for a while, the pressure gauge goes up to 2+ bar. Whether I release the pressure back down to 1bar or not, the pressure gauge eventually goes back down to zero.
A heating engineer suggested it was a faulty expansion vessel which I reolaced but the problem hasn't gone away
Someone said it could be the pressure relief valve but I dont see how this would cause the pressure to keep going up once it's set to 1bar.
Any suggestions would be greatly appreciated.

 

[SimonG]

Did you check the expansion vessel before replacing?

Gets expensive chucking parts at something when you dont know what you are doing.

Rather than listening to suggestions get somebody out who knows what they are doing.

 

[lame plumber]

ditto the above advice

 

[Dave Walker]

Your response and understanding of how the pressure relief valve not being at fault shows you need to get a Oftec engineer in.

 

[Best]

Probably could have been fixed using free materials.