Boiler not working after moving radiator

[conall]

One of my radiators was moved. After being replaced, each rad in the house was checked for airlocks, but water came from each. When swithched on, the boiler (Potterton) started banging after a minute or two. I then checked the pump for air and some did escape. After this, the banging ceased - however, the boiler only runs for a few minutes - one of the pipes gets very hot - then it cuts out. There is a swishing noise which I assume to be the pump. Any ideas what the problem is - could there still be an airlock in the system - or is the pump damaged ?

 

[ChrisR]

Problem is that a pump won't pump if it has (any) air in it. Check around where the boiler pipes go into the hot water cylinder, often there's a bleed point there. Check there's ploenty water in the header tank. Make sure you're bleeding the system with the mtorized valve(s) open - ie , eg,push small lever on end to "manual" position.
If all else fails try turning the pump round to push the air to where it can be bled out - then turn it back again!

 

[conall]

Thanks for the advice. I unsrewed the main nut in the centre facing of the pump and started the boiler. The pump was turning alright and a little water escaping from where I had removed the nut. I left it run for a few minutes with the nut out and eventually some air escaped. Boiler is now working fine so I think removing the nut and allowing to run allowed the trapped air to escape.

 

[corgiman]

Problem is that a pump won't pump if it has (any) air in it. Check around where the boiler pipes go into the hot water cylinder, often there's a bleed point there. Check there's ploenty water in the header tank. Make sure you're bleeding the system with the mtorized valve(s) open - ie , eg,push small lever on end to "manual" position.
If all else fails try turning the pump round to push the air to where it can be bled out - then turn it back again!

Thats a brilliant bit of advice and have had cause to use that me self, blast primary airlocks to wosit.