you need to drain at least a bucket or two
then the prv might re-seat itself,but there could be just a bit of dirt from stopping this
if thats the case just replace it
the pressure inside the ev should be about .8
the actual system pressure should be about 1.5 bar when it is cold and disconnect the filling loop when this is done.
use a simple tyre guage to check the pressure in side the ev
don't use the pressure guage on the unit , that is only for telling you the system pressure
also when you only got air out of the ev that shows the diaphragm is not burst
good practise would be to add a pipe to the prv to drain outside
once you have done this it would be a good idea to clean the system and add an inhibitor
Ok so drain the system by turning the pressure release valve (bucket or 2)
Pump up the EV to .8
Clean the system and add inhibitor
repressurize and hope for the best right?