Radiators won't bleed - no pressure

[Lightfoot]

hi all,
I've just noticed I had a couple of radiators that needed bleed upstairs tonight in our new home. I started to bleed the radiators and noticed that while I was able to let alone ir out, it was not followed by water. After doing this a few times I noticed the radiators where getting cooler and I was making the issue worse....‍....

So, I must need to add more pressure to the system I though. We have an outside oil burner and a pressurised central heating system so I went outside and had a look at the pressure gauge beside the red expansion vessel at the burner. It read 0.5bar, so I opened the valve to add more water to the system and the pressure will rise to above 1 bar, but as soon as the system gets to 1bar, something turns on and the pressure drops back down to where it was as soon as the valve is closed!??! I tried turning the boiler off and pressurise the system, but the pressure again drops as soon as the valve is closed.

Any ideas on what might be causing this??

 

[oilhead]

When you re pressurise the boiler, when the pressure switch is satisfied, the pump starts and creates a low pressure area. This is normal, and you need to continue pressurising the boiler. It will be best if you switch the boiler off, pressurise to the required pressure and then switch back on.

 

[Lightfoot]

Ah, cheers. Over thinking things again Got them all bleed tonight....