Hello fellow DIY'rs iv just got my heating system back up and running after some work on my house. There problem iv got is my radiators are not all workong. The rads upstairs are working fine but the rads downstairs some cold, some warm but warm at the top and cold at the bottom. the system iv got is glow worm space saver boiler and it has a sunvic timer with a sun vic motorised valve. do i need to bleed the rads downstairs?