Thanks for the reply. "Struggling" means that when I switch the boiler on, 9 times out of 10 nothing happens, the remaining time it fires up but stops after about 2-5 seconds.
I have bled all the radiators and the pump, but not tried anything else yet.
I have an Ideal Classic FF280 boiler based system. I had to drain the system to remove an unwanted radiator from the system and now it is now struggling to restart. There is a continuous low frequency hum from the motor, even with the boiler switched off. If I restart the boiler it occasionally...