Grant vortex losing pressure (moved from "forum informaton")

[Davidcgriffiths]

My central heating Grant Vortex Boiler losing pressure.
Initially it was every time the system shut off after the evening schedule, found each morning that pressure at zero.
Expansion cylinder changed for new
PSV changed Thursday and as run for 5 days now its ost pressure again. No leaks on radiators, any one any ideas.
Is there a high temperature overrun for the pump to keep it running when hot until below a certain temp.
Scratching my head on this one.

 

[BoilerBob]

Expansion hose blocked. Bob

 

[BoilerBob]

Also drop the pressure in the expansion vessel to 0.8 bar. Bob

 

[Davidcgriffiths]

Thanks will check in morning