Baxi 105 E Losing water pressure

[Jamieson01]

I have a Baxi 105e and have carried out a couple of repairs in the time i have lived in this house, this problem is baffling me tho'.

the system needs water topped up after a very short time. i can get up in the morning pressurise up to 2 bar then leave system off and come back an hour later and it's back to zero. however if i switch the heating on the pressure is maintained. i have checked all valves and radiators, i have also checked the manifold in the bathroom which feeds the upsairs rads. all showing no leaks.i have just tonight checked the overflow outside and this is dripping ever so slightly. what could be causing the water to be dumped outside???? and how do i fix it????

please help it's doing my head in!!!

 

[namsag]

NEW pressure relief valve req . , bottom right hand corner held in place with allen screw and the nut on pipe to outside

 

[clf-gas]

Could try topping the pressure up and turning the valve to release a few times to see if this will shift any trapped particles.

Would think a new valve though, very easy to DIY.