potterton power max he pressure vessel

[Jeff123]

Hi all, I'm new here so hear goes.
I have a potterton power max he, I've had some Ch pressure issues which I traced to a faulty pressure relief valve
Which is now on order but when I went to check the pressure vessel's the external one was ok but when I put the
Pump/gauge on the primary one, water came out and with a small pump I could hear bubbles.
So my question is
A, do I need to change the primary vessel or will the external one do the job
B, is it this that damaged the PRV
One other thing, with the boiler off its at 1.5bar and running it climbs to 2.3bar
Are these differences because of the primary vessel?

Thanks Jeff