Can anyone help. Took a rad off for decorating, and have just put it back on the wall. Connected it up and opened up the rad valves with the boiler off. Obviously pressure dropped so I used internal filler to fill it up to 1.2ish bar. I bled the rads and topped up system again. When i switched on the boiler and turned up the room stat, the boiler just whirrs, it fires up for a sec then switched straight off. It doea the same when i use the hot tap, doesnt get hot, just clicks off. So now the rads arent getting hot and nor is the water! be really grateful for some help