Heatline combi boiler pressure issue

[iaxgls]

HI,
I am having a combi boiler pressure issue (Heatline boiler, 5 yrs old), the pressure guage keeps dropping below 1, and when i wake up in the morning it has dropped completely to nil.
eg. yesterday at 7 am i increased the pressure to about 1.4, the heating was on periodically during the day, at about 7 pm i went out, and the pressure was still at about 1.35 (the heating had been off for about 45 mins by that point), i came home at about midnight, and the pressure was at about 1, and the light started flashing, when i work up this morning the pressure was at 0.
I am able to fill up water using the pressure loop and then it works perfectly well, but cant understand why the pressure guage keeps droppping.

When the pressure guage is showing nil, if i bleed the radiators there is no apparent loss in the pressure at which the water comes out.

I live in a 1st floor flat, and there are no visible signs of leaks either in my flat, or in the flat below me, im pretty sure the issue has to be with the boiler.
I have looked at the exit pipe out the window and it seems to be dry/mildly wet, but its difficult to confirm if it is coming from the boiler or just outside moistness.
I have had a couple of plumbers over who seem to scratch their head and are not sure what to do.

any thoughts greatly appreciated, its cold

Thanks
IAXGLS

 

[tj351011]

if you are losing pressure you are losing water if there is no apparent leaks in your flat it must be leaking outside through the pressure relief pipe.this usually means the pressure expansion vessel has lost its charge or failed. OR the pressure relief valve is faulty. either way its best left to a boiler engineer to check both components and replace the faulty one