Very noisy radiators - bubbling sounds

[lee22]

We have recently had some pipework modified in our kitchen, These pipes were feeding the radiator in our passage.
There was a maize of them running under our kitchen cupboards, some of which did not need to be in use so we had them removed and now there are only 2 pipes instead of 4.
All the radiators were bled by the person doing the job but now when we switch on our heating all of the radiators are making a lot of noise. It sounds like a bubling noise or water constantly flowing in them.
Does anyone know if this is just down to there being a lot of air in the systems and it just needs bleeding?
Can this cause any damage?
Also, there were no chemicals put in to the system when it was refilled - could this cause problems in the future?
The boiler is brand new, fitted in Dec 07, and is a condensing combi.

 

[corgiman]

is probably air

turn off the system over night and bleed the rad in the morning before turning it back on

also dont forget to re pressurize the system if it needs it.

 

[lee22]

thank you for this info.
We did bleed them and they were fine for one night but they are making the same noises again.
Do we need to keep bleeding them? Is it something that can take a bit of time?